Category Archives: Fungi

Fungi, Plant Pathogens

Plasmopara constantinescui Voglmayr & Thines 2007

California Pest Rating for
Plasmopara constantinescui Voglmayr & Thines 2007
Pest Rating: B
PEST RATING PROFILE

Initiating Event:

On August 8, 2017, diseased leaves of Impatiens walleriana plants were collected, from a retail nursery in Placer County, by Placer Agricultural County officials and sent to the CDFA Plant Pathology Laboratory for diagnoses.  The plants had been shipped from a different nursery in San Joaquin County.  Cheryl Blomquist, CDFA plant pathologist, identified the downy mildew pathogen, Plasmopara constantinescui, as the cause for the disease.  The pathogen was assigned a temporary ‘Q’ rating.  Consequently, the infected plants, received at Placer County, will be destroyed by County officials (Walber, 2017).  Impatiens walleriana plants related to the shipment from San Joaquin County were double-bagged and disposed at a landfill, by the nursery (Khan, 2017).  The risk of introduction and establishment of this pathogen in California is assessed and a permanent rating is herein proposed.

History & Status:

Background:   Plasmopara constantinescui is an obligate oomycete plant pathogen that causes downy mildew disease in its host plants.  Presently, the host range for the pathogen only includes Impatiens species, belonging to the plant family Balsaminaceae.

Plasmopara constantinescui was originally described as Bremiella sphaerosperma from Impatiens in eastern Russia and northeastern North America (Constantinescu, 1991).  However, after molecular phylogenetic analyses of DNA sequences, B. sphaerosperma was found to belong to the genus Plasmopara and transferred there accordingly.  Furthermore, as there already existed, within Plasmopara, a species by the same epithet, the newly-transferred pathogen was given a new epithet, P. constantinescui (Voglmayr & Thines, 2007).  This species was also shown to be closely related to Plasmopara obducens, which is a common, widely distributed pathogen of several species of Impatiens in the Northern Hemisphere, including California (Constantinescu, 1991; Voglmayr & Thines, 2007).

Hosts:  Impatiens sp. (impatiens), I. capensis (jewel weed), I. noli-tangere (western touch-me-not), I. pallida (pale touch-me-not) (Constantinescu, 1991; Farr & Rossman, 2017).  Plasmopara constantinescui was recently detected in Impatiens walleriana (buzzy lizzy) plants (see: ‘Initiating Event’.) 

Symptoms:  Pale yellowish to ochre, round to irregular, and scattered spots appear on the upper surface of leaves.  These spots are small (1-6 mm-diam.), vein-limited, and with margins that are indistinct to reddish brown or violaceous.  They rarely coalesce and cover larger areas.  White to greyish or yellowish downy growth of sporangiophores of the oomycete develop in patches on the underside of the spots (Constantinescu, 1991).  It is likely that, similar to other downy mildew-causing pathogens, Plasmopara constantinescui attacks and spreads rapidly in young, tender green leaf, shoot, and blossom tissue (Agrios, 2005).

Disease development: Generally, downy mildew pathogens overwinter as thick-walled resting spores called oospores in plant debris in the soil or on weed hosts, and as mycelium in infected, but not dead, twigs.  Downy mildew develops and is severe under conditions that favor periods of prolonged leaf wetness and high relative humidity during cool or warm, but not hot, periods.  During rainy period in spring, the oospores germinate to produce a sporangium.  The sporangium or its zoospores are transmitted by wind or water to wet leaves near the ground where they infect through stomata of the lower leaf surface.  Mycelium develops and spreads into intercellular spaces of leaves.  When it reaches the sub-stomatal cavity, it forms a cushion from which sporangiophores arise and grow through the stoma.  Sporangia are produced at the tips of the sporangiophores and are transmitted by wind or rain to nearby non-infected plants (Agrios, 2005; Daughtrey et al., 1995).  In pathogenicity tests, Plasmopara constantinescui was able to cause systemic shoot infection of Impatiens walleriana (Personal communication: Suzanne Latham, CDFA plant pathologist).

Dispersal and spread: Wind, rain/water splash, infected plants and infected plant debris.

Damage Potential: While estimates of crop losses caused particularly by Plasmopara constantinescui have not been reported, generally, downy mildews can cause significant losses in short periods of time. Affected plants may result in defoliation, flower drop, and stem rot, similar to Impatiens walleriana plants infected with the closely related downy mildew species, P. obducens (Crouch et al., 2014).  Nurseries, private and public gardens, and landscape plantings may be at particular risk of contracting downy mildew disease caused by P. constantinescui.  Fungicidal control of the pathogen is possible, but may be difficult.  Under cool wet weathers, downy mildews are often uncontrollable and checked only when the weather turns dry and hot (Agrios, 2005).

Worldwide Distribution: Asia: Eastern Russia (formerly USSR); North America: Canada, USA (Indiana, Massachusetts, Wisconsin, Iowa, Maryland, Minnesota, Virginia, South Carolina, and California) (Constantinescu, 1991; Farr & Rossman, 2017; Voglmayr & Thines, 2007; CDFA Pest and Damage Record 2017).

Official Control:  Bremiella sphaerosperma (synonym of Plasmopara constantinescui) is on the ‘Harmful Organism List’ for Brazil (USDA PCIT, 2017).  Presently, P. constantinescui has a Q rating in California.

California Distribution:  Based on the source of diseased Impatiens, Plasmopara constantinescui is present in San Joaquin County

California Interceptions:  One intrastate interception in Placer County (see: Initiating Event).

The risk Plasmopara constantinescui would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: The downy mildew oomycete, Plasmopara constantinescui requires prolonged periods of leaf wetness and high relative humidity during cool or warm, but not hot, periods. These conditions for infection and development of the pathogen is likely to limit its establishment in California, to coastal regions in particular.

Evaluate if the pest would have suitable hosts and climate to establish in California.

Score: 2

– Low (1) Not likely to establish in California; or likely to establish in very limited areas.

– Medium (2) may be able to establish in a larger but limited part of California.

– High (3) likely to establish a widespread distribution in California.

2) Known Pest Host Range: The host range for the pathogen is limited to Impatiens

Evaluate the host range of the pest.

Score: 1

– Low (1) has a very limited host range.

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

3) Pest Dispersal Potential: Spores are produced in abundance. The pathogen is transmitted via infected plant material, winds, and rain/water splash.

Evaluate the natural and artificial dispersal potential of the pest.

Score: 3

– Low (1) does not have high reproductive or dispersal potential.

– Medium (2) has either high reproductive or dispersal potential.

– High (3) has both high reproduction and dispersal potential.

4) Economic Impact: If left uncontrolled, downy mildews can cause significant losses in short periods of time. Affected plants may result in defoliation, flower drop, and stem rot, thereby lowering crop yield and value in increasing production costs largely due to administration of control measures.  Fungicidal control of the pathogen is possible, but may be difficult.  Under cool wet weathers, downy mildews are often uncontrollable and checked only when the weather turns dry and hot.

Evaluate the economic impact of the pest to California using the criteria below.

Economic Impact: A, B, C, D.

A. The pest could lower crop yield.

B. The pest could lower crop value (includes increasing crop production costs).

C. The pest could trigger the loss of markets (includes quarantines).

D. The pest could negatively change normal cultural practices.

E. The pest can vector, or is vectored, by another pestiferous organism.

F. The organism is injurious or poisonous to agriculturally important animals.

G. The organism can interfere with the delivery or supply of water for agricultural uses.

Economic Impact Score:  3

– Low (1) causes 0 or 1 of these impacts.

– Medium (2) causes 2 of these impacts.

– High (3) causes 3 or more of these impacts.

5) Environmental Impact:  Downy mildew disease caused by Plasmopara constantinescui could significantly impact home/urban, private and public gardens, and landscape plantings.

Evaluate the environmental impact of the pest on California using the criteria below.

Environmental Impact: E

A. The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.

B. The pest could directly affect threatened or endangered species.

C. The pest could impact threatened or endangered species by disrupting critical habitats.

D. The pest could trigger additional official or private treatment programs.

E. The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings

Environmental Impact Score: 2

– Low (1) causes none of the above to occur.

– Medium (2) causes one of the above to occur.

– High (3) causes two or more of the above to occur.

Consequences of Introduction to California for Plasmopara constantinescui:

Add up the total score and include it here. 11

-Low = 5-8 points

–Medium = 9-12 points

-High = 13-15 points

6) Post Entry Distribution and Survey Information: Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included.

Evaluation is ‘Low’.  Based on the source of diseased Impatiens, Plasmopara constantinescui is only present in San Joaquin County.

Score: (-1)

-Not established (0) Pest never detected in California, or known only from incursions.

–Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).

-Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.

-High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

Final Score:

7) The final score is the consequences of introduction score minus the post entry distribution and survey information score: (Score)

Final Score:  Score of Consequences of Introduction – Score of Post Entry Distribution and Survey Information = 10.

Uncertainty:  

None.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Plasmopara constantinescui is B.

References:

Agrios, G. N.  2005.  Plant Pathology fifth edition.  Elsevier Academic Press, Massachusetts, USA.  922 p.

Calflora.  2017.  Information on California plants for education, research and conservation. [web application]. 2017. Berkeley, California. The Calflora Database [a non-profit organization].  http://www.calflora.org/

Constantinescu, O. 1991. Bremiella sphaerosperma sp. nov. and Plasmopara borreriae comb. nov. Mycologia 83: 473-479.

Crouch, J. A., M. P. Ko, and J. M. McKemy.  2014.  First report of impatiens downy mildew outbreaks caused by Plasmopara obducens through the Hawai’ian Islands.  Plant Disease, 98: 696.  DOI: https://doi.org/10.1094/PDIS-10-13-1017-PDN

Daughtrey, M. L., R. L. Wick, and J. L. Peterson.  1995.  Downey mildews.  Part I. infectious diseases, diseases caused by fungi.  Compendium of flowering potted plant diseases.  APS Press, the American Phytopathological Society.  38-38 p.

Farr, D. F., and A. Y. Rossman.  2017.  Fungal Databases, U. S. National Fungus Collections, ARS, USDA. Retrieved September 7, 2017, from http://nt.ars-grin.gov/fungaldatabases/

French, A. M. 1989. California Plant Disease Host Index. California Department of Food and Agriculture, Sacramento (Updated online version by T. Tidwell, May 2, 2017).

Khan, S.  2017.  Email from S. Khan, CDFA Pest Exclusion, to T. Walber, CDFA Interior Pest Exclusion, and J. Chitambar, CDFA, dated 9/19/2017. 4:43 pm.

USDA PCIT.  2017.  USDA Phytosanitary Certificate Issuance & Tracking System. Retrieved September 7, 2017. 4:19:24 pm CDT.  https://pcit.aphis.usda.gov/PExD/faces/ReportHarmOrgs.jsp.

Voglmayr, H., and M. Thines.  2007.  Phylogenetic relationships and nomenclature of Bremiella sphaerosperma (Chromista, Peronosporales). Mycotaxon 100: 11-20.

Walber, T.  2017.  Email from T. Walber, CDFA Interior Pest Exclusion, to J. Chitambar, CDFA, dated 9/8/2017, 9:44 am.

Responsible Party:

John J. Chitambar, Primary Plant Pathologist/Nematologist, California Department of Food and Agriculture, 3294 Meadowview Road, Sacramento, CA 95832. Phone: 916-262-1110, plant.health[@]cdfa.ca.gov.

Pest Rating: B

Posted by ls

Fungi, Plant Pathogens

Phytophthora cactorum (Lebert & Cohn) J. Schröt. 1886

2 Comments
California Pest Rating Proposal for
Phytophthora cactorum (Lebert & Cohn) J. Schröt. 1886
Pest Rating: B
PEST RATING PROFILE
Initiating Event:

None.  The current risk and status of Phytophthora cactorum in California are reassessed and a permanent rating is proposed.

History & Status:

Background:  Phytophthora cactorum is an oomycete pathogen that has a very wide host range and can cause a wide range of disease symptoms including, root rot, collar and crown rot, fruit rot, and stem canker, usually in conjunction with other Phytophthora spp. in its hosts.  Phytophthora root and crown rot disease are among the most important soilborne diseases of stone fruits (Brown & Mircetich, 1995).  It is widespread in temperate regions of all continents and occurs in soils of natural forests, agricultural fields and orchards.  It can persist and spread in different environments and is capable of surviving in the soil as a saprophyte and by producing resting spores.

Phytophthora cactorum is widespread in California and has been found in several counties (see: “California Distribution”).  In California, P. cactorum has been found in several hosts: apple, avocado, apricot, American plum, European plum, Japanese plum, Myrobalan plum, sour cherry, sweet cherry, sweet almond, Mabaleb cherry, cherry laurel, peach, nectarine, pear, Southern California walnut, Northern California walnut, English walnut, strawberry, oval kumquat, sweet orange, kiwifruit, peony, rose, rhodendron, tomato, garden rhubarb, lilac, lily, calla lily, Didier’s tulip, tulip, garden snapdragon, western vervain, virbinum, blue blossom ceanothus, million bells, safflower, wild oats, daphne, white fir, Pacific madrone, chamise, manzanita, wild oats, coyote brush, incense cedar, beefwood, deodar cedar, eucalyptus, California buckthorn/coffeeberry, buckthorn, California flannelbush, toyon, common hop, holly, spicebush, carob, savin juniper, juniper, English laurel, redbay, Frasier’s photinia, chokeberry, Ponderosa pine, sticky cinquefoil, Formosa fire thorn, fire thorn, California live oak, valley oak, oak, cork oak, southern live oak, Indian hawthorn, redwood, giant sequoia, yew, and sticky monkey flower (French, 1989, CDFA Pest Damage Records).  The pathogen has also been recovered from various habitats including flowing water, stream and ditch banks, residential and public gardens, recreational areas, orchards, forests, and nurseries (Yakabe et al., 2009; CDFA Pest Damage Records).

Hosts: Phytophthora cactorum has a very wide host range of plants belonging to several families including, Aceraceae, Apocynaceae, Apiaceae, Araliaceae, Cactaceae, Cucurbitaceae, Cornaceae, Ebenaceae, Ericaceae, Fagaceae, Geraniaceae, Grossulariaceae, Hippocastanaceae, Juglandaceae, Lauraceae, Liliaceae, Oleaceae, Pinaceae, Proteaceae, Polygonaceae, Rutaceae, Rosaceae, Salicaceae, Solanaceae, Sterculiaceae, and Violaceae (CABI, 2017).

Farr and Rossman (2017) include 1332 records of hosts for Phytophthora cactorum and its synonyms.  Hosts include: Abies alba (silver fir), A. amabilis (Pacific silver fir), A. balsamea (balsam fir), A. balsamea var. phanerolepsis, A. concolor (white fir), A. firma (momi fir), A. fraseri (Fraser fir), A. magnifica var. shastensis (Shasta red fir), A. procera (noble fir), Abies sp., Acacia sp. (wattles/acacias), Acer spp. (maples), Actinidia chinensis (kiwi), A. deliciosa (fuzzy kiwifruit), Adenostoma fasciculatum (chamise), Aesculus hippocastanum (horse chestnut), Aesculus sp. (buckeye and horse chestnuts), Agonis flexuosa (Jervis Bay Afterdark), Alnus glutinosa (common alder/black alder), A. incana (grey alder/speckled alder), A. oregana (Oregon alder), Amygdalus persica (peach), Ananas comosus (pineapple), Anemone coronaria (poppy anemone/Spanish marigold), Angelica sp. (angelica), Annona cherimola (cherimoya), Antirrhinum sp., A. majus (snapdragon), Aquilegia sp. (columbine), Aralia cordata (spikenard), A. elata (Japanese angelica-tree), Arbutus menziesii (Pacific madrone/madrone), Arctostaphylos spp. (manzanita), Aster spp. (asters), Aucuba japonica (spotted laurel/Japanese laurel), Avena fatua (common wild oat), Baccharis pilularis (coyote brush),  Banksia spp. (banksia), Begonia sp. (begonia), Beta vulgaris var. crassa (beets), Betula lutea (yellow birch), B. pendula (silver birch), Betula sp. (birch), Boehmeria spp. (false nettles), Brassica oleracea var. bullata (Brussel sprouts), Brassica sp. (mustard), Brassolaeliocattleya sp. (orchid), Bryophyllum pinnatum (airplant), Buxus sp. (boxwood), Cactus sp., Calceolaria integrifolia (bush slipperwort), Calceolaria sp. (sweetshrub), Calibrachoa sp. (million bells), Callistephus chinensis (China aster), Calocedrus decurrens (California incense cedar), Calycanthus floridus (eastern sweetshrub), C. occidentalis (spicebush), Calytrix angulata (yellow starflower), Capsicum annuum (cayenne pepper), C. frutescens (chili pepper), Carica papaya (papaya), Carthamus tinctorius (safflower), Carya illinoinensis (pecan), Castanea sativa (sweet chestnut), Castanea sp., Casuarina sp. (beefwood), Catharanthus roseus (Madagascar periwinkle), Ceratonia siliqua (carob), Cereus spp., Cattleya sp. (cattleya orchid), Ceanothus thyrsiflorus (blue blossom ceanothus), Cedrus deodara (deodar cedar), Ceratonia siliqua (carob tree),  Chamaecyparis spp. (false cypress), Chrysalidocarpus lutescens (areca palm/butterfly palm), Chrysanthemum spp., Citrullus lanatus (watermelon; syn. C. vulgaris), Citrus aurantium (bitter orange), C. grandis (pomelo; syn. C. maxima), C. limon (lemon), C. limonia (Mandarin lime), C. sinensis (sweet orange), Citrus sp., Clarkia spp., Cleome spp.,  Cocos nucifera (coconut), Cornus sp. (dogwood), C. sericea (western dogwood), Cucumis  melo var. inodorus (Kolkhoznitsa melon), C. melo var. reticulatus (galia melon), C. sativus (cucumber), C. pepo (field pumpkin), Dahlia sp., Daphne cneorum (rose daphne/garden flower), D. mezereum (February daphne), D. odora (winter daphne), Daphne sp., Dendrobium sp. (dendrobium orchid), Dianthus caryophyllus (carnation), Daucus carota (carrot), Diospyros kaki (persimmon), Diplacus aurantiacus (syn. Mimulus aurantiacus, sticky monkeyflower), Eriobotrya japonica (loquat), Echinochloa crus–galli (barnyardgrass), E. eyriesii, Epidendrum spp. (Epidendrum orchids), Erica hyemalis (cape heath), Eucalyptus spp., Fagus sp. (beeches) F. sylvatica (common beech), Fragaria spp. (strawberry), F. ananassa (strawberry), F. chiloensis (Chilean strawberry), F. vesca (wild strawberry), Frangula californica (coffeeberry/California buckthorn), Fraxinus spp., (ash), Fremontia californica (California flannelbush; syn. Fremontodendron californicum (California flannelbush), Fremontia sp., F. mexicanum (Mexican flannelbush), Fortunella margarita (oval kumquat), Galeandra baueri (orchid), Gladiolus sp., Glycine max (soybean), Hesperocyparis macrocarpa (syn. Cupressus macrocarpa, Monterey cypress), Heteromeles arbutifolia (toyon), Hibiscus spp. (rosemallows), Humulus lupulus (common hop), Ilex sp. (holly), Juglans californica (California black walnut), J. hindsii (Northern California walnut/Hinds’ black walnut), J. nigra (black walnut), J. pyriformis, J. regia (English walnut), Juglans sp., Juniperus procera (African juniper), J. sabina (savin juniper), Juglans. sp., Kalanchoe spp., Lactuca sativa (lettuce), Laeliocattleya sp. (orchid), Lilium spp. (lily), Lycopersicon esculentus (tomato; syn.  Solanum lycopersicum), Malus domestica (apple), Malus sp., M. sylvestris (European crab apple), Mespilus germanica (medlar), Panax quinquefolius (American ginseng), Pelargonium spp. (pelargonium), Paeonia lactiflora (Chinese peony/common garden peony), Paeonia spp. (peony), Panax spp. (ginseng), Persea americana (avocado), P. borbonia (redbay), Photinia spp. (photonia/chokeberry), Picea spp. (spruce), Pinus spp. (pine), Populus alba (silver-leaf poplar), Potentilla glandulosa (syn. Drymocallis glandulosa, sticky cinquefoil), Prunus armeniaca (apricot/American plum), P. avium (sweet cherry), P. cerasus (sour cherry), P. dulcis (almond; syn. P. amygdalus), P. ilicifolia (hollyleaf cherry/evergreen cherry), P. laurocerasus (cherry laurel/English laurel), P. mahaleb (mahaleb cherry), P. mume (Chinese plum/Japanese apricot), P. persica (peach), P. persica var. nucipersica (nectarine), P. salicina (Japanese plum), Prunus sp., Pyracantha coccinea (scarlet firethorn), , P. koidzumii (Formosa firethorn), Pyracantha sp. (fire thorn), Pyrus communis (European pear), Quercus agrifolia (California live oak/coast live oak), Q. falcata (southern red oak), Q. lobata (valley oak), Q. petraea (durmast oak), Q. robur, (English oak), Quercus sp., Q. suber (cork oak), Q. virginiana (live oak), Rhamnus (Frangula) californica (California coffeeberry), Rhaphiolepis indica (Indian hawthorn), Rheum rhaponticum (false rhubarb), Rheum hybridium (rhubarb), Rhododendron spp., (azalea), Ribes spp., (currants), R. lobbii (Lobbs gooseberry), R. uva-crispa (gooseberry), Rosa sp. (rose), Salix sp. ( willow), Sequoiadendron giganteum (giant sequoia), Solanum (nightshade), S. lycopersicum (tomato), Syringa vulgaris (lilac), Syringa sp., Taxus sp. (yew), Theobroma cacao (cocoa), Tulipa sp. (tulip), Tulipa gesneriana (Didier’s tulip), Viola sp. (violet), Vanda sp. (Vanda orchid), Verbena sp., V. lasiostachys (western vervain), Viburnum spp., Vicia faba (fava bean/broad bean), Vicia sp. (vetch), V. unguiculata, Vigna unguiculata (cowpea; syn. V. sinensis), V. cylindrica (catjang), V. sesquipedalis (yardlong bean), Vitis vinifera (grape ), Zea mays (corn), Zantedeschia sp. (calla lily) (CABI, 2017; Farr & Rossman, 2017; French, 1989; CDFA Pest Damage Records).

Symptoms: Phytophthora cactorum attacks a wide range of host plants causing varied symptoms, depending on the host.  Symptoms include root rot, collar and crown rot, fruit rot, stem cankers, leaf blight, wilts and seedling blights.  This pathogen can cause pre- and post-emergence damping-off disease in several plant species.  It has been reported to reduce sprouting and kill seedlings of beech, and cause seedling blight in Pinus spp., Salix scoulerana, and Robinia spp. (CABI, 2017).

On apple, pear and other woody hosts, P. cactorum causes crown, collar and root rot.  Crown rot affects rootstock tissue from the graft union down to the tips of the primary roots, whereas collar rot affects the scion above the graft union or slightly above the soil line.  Root rot refers to symptoms that appear beyond the proximal junction of primary roots to crown tissue (Cox, 2014).   Above ground symptoms are indicative of an impaired root system and include general stunting with reduced terminal growth and small, chlorotic leaves.  Symptom expression depends on the amount of infected crown or root tissue and their rate of destruction.  Young trees are usually killed by the pathogen since their root systems and crown regions are not as developed as those of mature trees.  Generally, crown rots advance rapidly and trees fall and die soon after the first warm spring.  Their leaves wilt, dry, and remain attached to the tree (Adaskaveg et al., 2009; Gubler & Teviotdale, 2009).  Trees with root rot slowly decline and eventually die over several seasons. At early stages of tree decline, removing the bark reveals orange to reddish brown necrotic lesions in cambium tissue.  A thin, dark delineated margin is evident at the junction of healthy tissue and the expanding lesion which, over time, turns dark brown as it gets colonized by secondary fungi and bacteria.  Symptoms can extend through the root system resulting in a lack of fibrous and feeder roots.  Crown lesions can extend to the primary roots and up to the graft union, while collar lesions can extend up to a meter up from the graft union.  On dissection, collar infections may appear striped in the inner phloem tissue and, sometimes, result in weeping though cracked barked tissue (Cox, 2014).   Phytophthora cactorum also causes fruit rot in apple and pear, producing pale olive and dark brown lesions in apple and pear respectively.  Those lesions are diffusely marbled or uniformly colored with softly delineated margins (Covey et al., 2014).

In Rhododendrons affected by Phytophthora root rot, roots become necrotic and leaves turn chlorotic, wilt, roll downwards parallel to the midrib, and eventually turn brown.  In contrast, leaves of infected azalea become chlorotic, and then necrotic, but seldom wilt. Necrotic leaves eventually drop to the ground (Hoitink et al., 2014).

Infected trees may develop cankers on the stem or near the soil line with discoloration of infected bark, sometimes extending into the internal tissues (CABI, 2017).

Phytophthora cactorum can cause crown rot and root rot of strawberries.  Initial symptoms typically include plant stunting and small leaves.  Later, infected plants may collapse rapidly or gradually.  When cut open, brown discoloration of the crown vascular tissue or entire tissue is apparent.  While other Phytophthora species may be involved, P. cactorum is the most common species on strawberry (Koike et al., 2008).  Fruit is also infected by P. cactorum resulting in leather rot disease.  On green fruit, symptoms appear as dark brown areas or green areas with brown margins.  As the rot spreads, the entire fruit turns brown with a rough texture that appears leathery. Infected mature fruit may be slightly discolored or turn brown to dark purple.  Internally, vascular tissue to each seed is darkened, and in later stages of decay mature fruit becomes leathery.  Infected fruit have unpleasant odor and taste.  Under moist conditions, white mycelial growth may be present on the surface of fruit.  Green and mature fruit eventually become shriveled mummies (Ellis & Madden, 1998).

Disease development: P. cactorum can survive for several years, mainly as oospores (sexual spores) in soil and mummified fruit. The pathogen can also survive as chlamydospores (thick-walled asexual spores) (Erwin & Ribeiro, 1996) in orchard soil or mycelium in host tissue (Cox, 2014).  Similar to other Phytophthora spp., P. cactorum lives as a saprophyte in litter and in soil containing dead organic material and is favored by moist and moderate climates. In spring, and in saturated soil, oospores germinate to produce sporangia.  In free water, zoospores are produced within sporangia and liberated into water.  While oospores and chlamydospores form the primary inoculum, sporangia are the principal source of secondary inoculum (CABI, 2017).  Free water is required for infection, however, a high incidence of disease can occur with as little as 2 hours or less of wetness at 17-25°C.  Optimum temperature for infection is 21°C.   The most favorable temperatures for sporangia production are between 15 and 25°C, and optimally at 20°C.  No sporangia are produced at 10 and 30°C (Ellis & Madden, 1998).   Sporangia can germinate directly or indirectly by producing zoospores.  Zoospores allow a population to increase rapidly and disperse widely in films of free water.  Zoospores are expelled from sporangia under suitable temperature and moisture conditions and swim by means of their flagella towards their host in response to root exudates.  Once a zoospore comes in contact with a root it germinates producing a germ tube which penetrates the root directly under waterlogged soil conditions.   More mycelium develops and eventually, oospores (sexual spores) are produced and serve as resting structures that can survive for several years.  (CABI, 2017).

Transmission: Like most Phytophthora species, P. cactorum is soil-borne and water-borne and may be spread to non-infected sites through infected plants, nursery and planting stock, and seedlings, soil, run-off and splash irrigation and rain water, and contaminated cultivation equipment, tools, and boots.  Under high moisture and windy conditions, sporangia may be airborne and important in spread of diseases such as leather rot of strawberry.  The pathogen is not seed-borne but can be spread by infected seedlings and through soil or plant debris containing oospores or chlamydospores contaminating seed samples (CABI, 2017).  Furthermore, irrigation water from canals, rivers, and ponds can be contaminated with Phytophthora spp. (Brown & Mircetich, 1995).

Damage Potential: Specific crop losses caused by Phytophthora cactorum alone may be difficult to assess as more than one species of Phytophthora may cause diseases with symptoms similar to those caused by P. cactorum and may be present in infected hosts. Nevertheless, P. cactorum is a serious pathogen of a wide range of plant species. Infections of 88-97% apple and pear nursery stock material in commercial nurseries has been reported (Jeffers & Aldwinckle, 1988), and P. cactorum has been frequently detected in several ornamental nurseries within California (Yakabe et al., 2009).  Therefore, nurseries may be at risk and need to be monitored for this pathogen to ensure production and planting of disease-free nursery stock.

California’s native vegetation is also at risk of root and crown rot caused by P. cactorum and other Phytophthora spp., many of which are endemic (limited) to California, while some are rare, endangered, or threatened plants, e.g., Ribes spp. (currant/gooseberry), Monterey cypress, and Arctostaphylos spp. (manzanita) (Calflora, 2017; CNPS, 2017).  Introduction of Phytophthora species are a threat to plant health in Bay Area restoration sites, where nursery stock is planted for flood control or to mitigate environmental impacts.   Detections on madrone, toyon, oaks, sticky monkeyflower, and manzanitas in native stands indicate that P. cactorum is capable of becoming established in a variety of native plant habitats under a range of soil and environmental conditions and can have negative impacts on native vegetation.

Worldwide Distribution: Asia: China, India, Indonesia, Iran, Israel, Japan, Korea DPR, Republic of Korea, Laos, Lebanon, Malaysia, Pakistan, Philippines, Taiwan, Turkey, Vietnam; Africa: Egypt, Kenya, Morocco, Senegal, South Africa, Tunisia, Zimbabwe; North America: Bermuda, Canada, Mexico, USA; South America: Argentina, Brazil, Chile, Colombia, Peru, Uruguay, Venezuela; Europe: Austria, Belgium, Bulgaria, Croatia, Czech Republic, (former) Czechoslovakia, Denmark, Finland, France, Germany, Greece, Hungary, Ireland, Italy, Lithuania, Netherlands, Norway, Poland, Romania, Russian Federation, Russia (European), Serbia, Slovenia, Spain, Sweden, Switzerland, United Kingdom; Oceania: Australia, New Zealand; Central America and Caribbean: Cuba, El Salvador, Trinidad and Tobago (CABI, 2017; EPPO, 2017).

In the USA, Phytophthora cactorum has been reported from California, Florida, Maine, Michigan, Minnesota, New York, North Carolina, Ohio, South Carolina, Tennessee, Virginia, Washington (CABI, 2017; EPPO, 2017).

Official Control:  Presently, Phytophthora cactorum is the “Harmful Organism Lists” for Egypt, French Polynesia, Guatemala, India, Israel, Lebanon, and Nicaragua, while, Phytophthora spp. is on the “Harmful Organism Lists” for Canada, French Polynesia, Mexico, Namibia, Seychelles, South Africa, and the Bolivarian Republic of Venezuela (USDA PCIT, 2017).

California Distribution: Phytophthora cactorum is widely distributed within California.  From 2001-July, 2017, the pathogen was detected in Alameda, Butte, Contra Costa, Imperial, Los Angeles, Marin, Merced, Monterey, Placer, Sacramento, San Diego, San Francisco, San Mateo, Santa Barbara, Santa Clara, Santa Cruz, Siskiyou, Solano, Sonoma, and Stanislaus Counties (CDFA Pest Damage Records).

California Interceptions:  None reported.

The risk Phytophthora cactorum would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: Phytophthora cactorum has already established a large distribution under moist and cool to warm climates in California.

Evaluate if the pest would have suitable hosts and climate to establish in California.

Score: 2

– Low (1) Not likely to establish in California; or likely to establish in very limited areas.

– Medium (2) may be able to establish in a larger but limited part of California.

– High (3) likely to establish a widespread distribution in California.

2) Known Pest Host Range: The pathogen has a very wide host range.

Evaluate the host range of the pest.

Score: 3

– Low (1) has a very limited host range.

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

3) Pest Dispersal Potential: Phytophthora cactorum, like other Phytophthora, has high reproductive capability under moist conditions.  It is dependent on moisture for spore dissemination and plant infection.  It is soilborne and may be spread to non-infected sites through infected plants, nursery and planting stock, and seedlings, soil, run-off and splash irrigation and rain water, and contaminated cultivation equipment, tools, boots, rivers, canals, and ponds.  Therefore, it is given a high rating in this category.

Evaluate the natural and artificial dispersal potential of the pest.

Score: 3

– Low (1) does not have high reproductive or dispersal potential.

– Medium (2) has either high reproductive or dispersal potential.

– High (3) has both high reproduction and dispersal potential. 

4) Economic Impact: Damage caused by Phytophthora cactorum alone may be difficult to assess as more than one species of Phytophthora may be associated with root and crown rot of host tree.  Nevertheless, cactorum is a serious pathogen affecting production of several economically important hosts including, apple, pear, stone fruits, strawberry, ornamentals, and California native plants.  Nursery productions could be at risk. Controlling the disease would include soil water management and use of resistant varieties, thereby requiring changes in cultural practices and increase in crop production costs.

Evaluate the economic impact of the pest to California using the criteria below.

Economic Impact: A, B, D, G

A. The pest could lower crop yield.

B. The pest could lower crop value (includes increasing crop production costs).

C. The pest could trigger the loss of markets (includes quarantines).

D. The pest could negatively change normal cultural practices.

E. The pest can vector, or is vectored, by another pestiferous organism.

F. The organism is injurious or poisonous to agriculturally important animals.

G. The organism can interfere with the delivery or supply of water for agricultural uses.

Economic Impact Score: 3

– Low (1) causes 0 or 1 of these impacts.

– Medium (2) causes 2 of these impacts.

– High (3) causes 3 or more of these impacts.

5) Environmental Impact: In conjunction with other Phytophthora, P cactorum may be a contributor to root and crown disease of environmental plants. California’s native vegetation is at risk of root and crown rot damage caused by P. cactorum and other Phytophthora spp.  Certain native plants are endemic (limited) to the State, while some are rare, endangered, or threatened.  The pathogen is capable of becoming established in a variety of native plant habitats under a range of soil and environmental conditions and can have negative impacts on native vegetation.  Its association alone and with other Phytophthora spp. in infected forest and native tree and shrub hosts could result in lowered biodiversity, disrupted natural communities, and critical habitats.  Also, it may significantly impact ornamental plantings and home/urban gardening.

Evaluate the environmental impact of the pest on California using the criteria below.

Environmental Impact: A, B, C, E

A. The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.

B. The pest could directly affect threatened or endangered species.

C. The pest could impact threatened or endangered species by disrupting critical habitats.

D. The pest could trigger additional official or private treatment programs.

E. The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.

Environmental Impact Score: 3

– Low (1) causes none of the above to occur.

– Medium (2) causes one of the above to occur.

– High (3) causes two or more of the above to occur.

Consequences of Introduction to California for Phytophthora cactorum:

Add up the total score and include it here. 14

-Low = 5-8 points

-Medium = 9-12 points

                        –High = 13-15 points

6) Post Entry Distribution and Survey Information: Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included.

Evaluation is:

Score: (-3)

-Not established (0) Pest never detected in California, or known only from incursions.

-Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).

-Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.

–High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

 Final Score:

7) The final score is the consequences of introduction score minus the post entry distribution and survey information score: (Score)

Final Score:  Score of Consequences of Introduction – Score of Post Entry Distribution and Survey Information = 11

Uncertainty:  

None.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Phytophthora cactorum is B.

References:

Adaskaveg, J. E., J. L. Caprile, W. D. Gubler, B. L. Teviotdale.  2009.  Cherry: Phytophthora root and crown rot, pathogen: Phytophthora spp.  UCIPM Statewide Integrated Pest Management Program, University of California Agriculture & Natural Resources.  http://ipm.ucanr.edu/PMG/r105100711.html

Browne, G. T., and S. M. Mircetich.  1995.  Phytophthora root and crown rots.  In Compendium of Stone Fruit Diseases, Eds: J. M. Ogawa, E. I. Zehr, G. W. Bird, D. F. Ritchie, K. Uriu, and J. K. Uyemoto.  APS Press, The American Phytopathological Society. Pages 38-40.

CABI.  2017.  Phytophthora cactorum (apple collar rot) full datasheet.  Crop Protection Compendium. http://www.cabi.org/cpc/datasheet/40953

Calflora.  2017.  Information on California plants for education, research and conservation. [Web application]. 2017. Berkeley, California. The Calflora Database [a non-profit organization].  http://www.calflora.org/

CNPS.  2017.  Inventory of rare and endangered plants of California (online edition, v8-03 0.38).  California Native Plant Society, Rare Plant Program. Website http://www.rareplants.cnps.org [accessed 10 August 2017].

Covey, R. P. Jr., and D. C. Harris; revised by K. Cox.  2014.  Phytophthora fruit rot.  In Compendium of Apple and Pear Diseases and Pests Second Edition Eds. T. B. Sutton, H. S. Aldwinckle, A. M. Agnello, J. F. Walgenbach.  APS Press, The American Phytopathological Society.  Pages 41-42.

Cox, K.  2014.  Phytophthora collar, crown, and root rots.  In Compendium of Apple and Pear Disease and Pests Second Edition Eds: T. B. Sutton, H. S. Aldwinckle, A. M. Agnello, J. F. Walgenbach.  Pages 63-65.

EPPO.   2017.   Phytophthora cactorum (PHYTCC).  PQR database.  Paris, France: European and Mediterranean Plant Protection Organization.  https://gd.eppo.int/

Ellis, M. A., and L. V. Madden.  1998.  Leather rot.  In Compendium of Strawberry Diseases Second Edition Ed. J. L. Maas.  APS Press, The American Phytopathological Society.  Pages 33-35.

Erwin, D. C., and O. K. Ribeiro.  1996.  Phytophthora Diseases Worldwide. St Paul, Minnesota, USA: American Phytopathological Society Press.

Farr, D. F., and A. Y. Rossman.  2017.  Fungal Databases, U.S. National Fungus Collections, ARS, USDA. Retrieved July 31, 2017, from https://nt.ars-grin.gov/fungaldatabases/

French, A.M. 1989. California Plant Disease Host Index. California Department of Food and Agriculture, Sacramento (Updated online version by T. Tidwell, May 2, 2017).

Gubler, W. D., and B. L. Teviotdale.  2009.  Apple, Phytophthora root and crown rot (updated 3/2009).  UCIPM, University of California Agriculture & Natural Resources, Statewide Integrated Pest Management Program.  http://ipm.ucanr.edu/PMG/r4100511.html

Hoitink, D. M. Benson, and A. F. Schmitthenner; revised by D. M. Benson and S. N. Jeffers.  2014.  Phytophthora root rot.  In Compendium of Rhododendron and Azalea Diseases and Pests Second Edition Eds: R. G. Linderman and D. M. Benson.  Pages 5-10.

Jeffers, S. N., and H. S. Aldwinckle.  1988.  Phytophthora crown rot of apple trees: sources of Phytophthora cactorum and P. cambivora as primary inoculum. Phytopathology, 78: 328-335

Mircetich, S. M., and M. E. Matherton.  1976.  Phytophthora root and crown rot of cherry trees.   Phytopathology 66: 549-558.

USDA PCIT.  2017.  USDA Phytosanitary Certificate Issuance & Tracking System. Retrieved June 6, 2017. 11:48:29 am CDT.  https://pcit.aphis.usda.gov/PExD/faces/ReportHarmOrgs.jsp.

Yakabe, L. E., C. L. Blomquist, S. L. Thomas, and J. D. MacDonald.  2009.  Identification and frequency of Phytophthora species associated with foliar diseases in California ornamental nurseries.  Plant Disease, 93: 883-890.

Responsible Party:

John J. Chitambar, Primary Plant Pathologist/Nematologist, California Department of Food and Agriculture, 3294 Meadowview Road, Sacramento, CA 95832. Phone: 916-262-1110, plant.health[@]cdfa.ca.gov.

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 PEST RATING: B

Posted by ls

Fungi, Plant Pathogens

Uromyces transversalis

California Pest Rating for
Uromyces transversalis (Thüm.) G. Winter
Pest Rating: C
PEST RATING PROFILE
Initiating Event:  

None.  The status of Uromyces transversalis in California, is updated and the current rating is reviewed.

History & Status:

Background:  Uromyces transversalis is an autoecious rust pathogen that causes rust disease, commonly known as gladiolus rust, only in members of the family Iridaceae, including Gladiolus, Tritonia, Crocosmia, and Watsonia spp.  Gladiolus is the major host of the pathogen, while the other hosts are of lesser economic importance.  Of six rust pathogens that can infect gladiolus, U. transversalis is the most economically damaging one.

Uromyces transversalis is indigenous to eastern and southern Africa, where it was first detected on leaves of Tritonia securigera in 1876.  Almost a century later, the pathogen spread to the Mediterranean region and southern Europe.  During the 1960-70s it was reported from France, Italy, and Morocco, and from England by 1996 (USDA APHIS PPQ, 2007).

Gladiolus rust was first detected and confirmed in the United States in April 2006, from a gladiolus production farm in Manatee County, Florida, and later, in another commercial gladiolus farm in Hendry County, Florida (USDA APHIS PPQ, 2007).  Then, in May 2006, gladiolus rust was detected on hybrid gladiolus plants in a home garden in San Diego, California.  Consequently, an intensive 23 square mile survey was conducted and the rust pathogen was detected at one commercial nursery and two other residential sites (Blomquist et al., 2007).  Since 2006, the pathogen has been repeatedly detected in Florida and California.  The source of introduction of Uromyces transversalis into the USA is unknown.  The pathogen is known to occur in Mexico and has been intercepted in numerous shipments of cut flowers from Mexico dating back to 2004.  The initial detection in Florida was the result of trace-back investigations following an interception of rust-infected flowers in Hawaii that originated in Florida.  Infected Florida-produced gladiolus flowers were intercepted in Minnesota in 2008, which had, likewise, originated from one of the original infected Florida gladiolus producers (Preston, 2009).

In California, to date, the disease has been detected in over 680 samples submitted to the CDFA Plant Pest Diagnostics Laboratory.  Samples have come primarily from landscapes associated with residences, businesses, and municipalities from no fewer than twelve California counties, ranging from Solano County and San Francisco County in the northern region to San Diego County in the southern region where it was originally detected.  Samples have come from no fewer than 38 different California cities (CDFA Pest Detection Reports).  The wide distribution indicates that Gladiolus Rust is well beyond the possibility of eradication in California, and is, instead, a management issue.

In August 2006, the gladiolus rust pathogen, Uromyces transversalis, was deemed as actionable and reportable by the USDA.  In 2007, federal and state action was taken in accordance with the USDA APHIS’ ‘Gladiolus Rust National Eradication and Management Plan’ (USDA, 2007), whenever the pathogen was detected in commercial growing areas, domestic commerce, and residential areas.  The decision to go that route was made when the pathogen was still believed to be limited in distribution in Florida and California and eradication was thought to be feasible.    However, on May 15, 2015, APHIS revised the domestic response requirements for U. transversalis to no longer take domestic action or require others to take action when gladiolus rust is found in commercial growing areas, domestic commerce, and residential areas.  This revision was made because the pathogen has spread to the limit of its natural range, based on its current distribution, known biology, and plant hardiness zones in the United States.  However, APHIS will continue to regulate other gladiolus rust pathogens that are known to occur in the United States (USDA, 2015).

Transmission:  The primary pathways for introduction of the pathogen are by shipments of infected plants and cut flowers. Interceptions from commercial shipments and passenger baggage at ports-of-entry in Arizona, California, and Texas confirmed that cut flowers are the major pathway of gladiolus rust from other countries (USDA APHIS, 2007). A significant anecdotal observation of the close proximity of residential infections with cemeteries also comes as no surprise, considering the propensity of the public to use gladiolus cut flowers to decorate grave sites.  Long distance and local spread is by wind-blown spores. These airborne spores are easily dispersed by lightly brushing a symptomatic plant and can be spread by surface-contaminated clothing, equipment, corms, rhizomes, and flowers (USDA APHIS PPQ, 2007).

Symptoms: Symptoms are typical for a rust disease, with yellowish-brown (uredinia) or blackish-brown (telia) pustules on the leaves, either solitary or aggregated.  Uredinia develop first and produce urediniospores, followed by development of the telia, which produce teliospores.  Initial symptoms of gladiolus rust are the appearance of small, yellowish spots.  Later, the epidermis bursts open exposing pustules full of yellowish- orange spores.  Over time, pustules coalesce to form large lesions.  Rust pustules normally form on foliage, on both sides, but under heavy disease pressure, can also form on flower spikes. Severely infected plants fail to even flower or produce mature corms. The pustules are formed in lines that run “transversely” across the leaf veins (as opposed to round or amorphous pustules, as is normally the case with most rust fungi on monocots whose sori run longitudinally along the vein of the leaf).  These unique transverse pustules are useful for making field identifications of the rust (USDA, 2007; USDA APHIS PPQ, 2007).

Hosts:  All hosts belong to the family Iridaceae.  The primary/major host is Gladiolus hybrids (sword lily/gladiolus). Minor hosts include, Crocosmia aurea (falling stars), Freesia refracta (common freesia), Tritonia sp. (flame freesia), T. lineata, T. securigera, T. squalida, Watsonia sp. (bugle lily), W. angusta, W. densiflora, W. meriana, and W. borbonica (CABI, 2017; EPPO, 2017; Farr & Rossman, 2017).

Damage Potential:  Gladiolus rust is a serious disease in nurseries and, if left uncontrolled, can completely destroy commercial gladiolus crops.  Severely damaged plants do not flower and/or their corms do not ripen (USDA APHIS PPQ, 2007).  There are efficacious fungicides available that can control the pathogen, however the frequent treatments necessary to protect the product can be costly for producers (Schwartzburg, 2006).  Furthermore, gladiolus rust can be controlled with best management practices (USDA, 2015).

The pathogen has only rarely been found in commercial settings in California, possibly because production managers have taken pro-active measures to protect their crops against the pathogen by frequent scouting and preventive fungicide treatments.  An example of this is a large gladiolus cut flower producer in Santa Barbara County that is virtually surrounded by infected residences. The nursery staff routinely inspect and fungicide-treats the crop which is grown from new imported corms each year.  As further protection, a host-free period at the production grounds follows the harvest of the year’s crop (Scheck, 2012).

Worldwide Distribution: Africa: Kenya, Malawi, Mauritius, South Africa, Tanzania, Uganda, Zambia, Zimbabwe; North America: Mexico, USA (California, Florida); Central America and Caribbean: Costa Rica, Cuba, Martinique; South America: Argentina, Brazil; Europe: France, Italy, Malta, Spain; Oceania: Australia, New Zealand (CABI, 2017; EPPO, 2017; Farr & Rossman, 2017).

Official Control: Uromyces transversalis is on the ‘Harmful Organism Lists’ for the following countries:  Australia, Chile, China, Colombia, Ecuador, French Polynesia, India, Israel, Republic of Korea, Madagascar, Nauru, New Caledonia, Peru, Tunisia (USDA PCIT, 2017).

California Distribution:  Alameda, Contra Costa, Los Angeles, Orange, San Diego, San Francisco, San Mateo, Santa Barbara, Santa Clara, Santa Cruz, Solano, and Ventura Counties.

California Interceptions:  None reported.

The risk Uromyces transversalis would pose to California is evaluated below.

Consequences of Introduction: 

 1) Climate/Host Interaction: The ability for Uromyces transversalis to have suitable hosts and climate in order to establish in California is already illustrated by its state-wide distribution over the past eleven years.

Evaluate if the pest would have suitable hosts and climate to establish in California.

Score: 3

– Low (1) Not likely to establish in California; or likely to establish in very limited areas.

– Medium (2) may be able to establish in a larger but limited part of California.

– High (3) likely to establish a widespread distribution in California.

2) Known Pest Host Range: Gladiolus is the only major host for Uromyces transversalis.

Evaluate the host range of the pest.

Score: 1

– Low (1) has a very limited host range.

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

3) Pest Dispersal Potential: Uromyces transversalis has high reproduction and dispersal potential.

Evaluate the natural and artificial dispersal potential of the pest.

Score: 3

– Low (1) does not have high reproductive or dispersal potential.

– Medium (2) has either high reproductive or dispersal potential.

– High (3) has both high reproduction and dispersal potential.

4) Economic Impact: Gladiolus Rust is known to lower yields, could increase costs due to fungicide treatments for commercial producers, and could result in quarantines by other states or countries.

Evaluate the economic impact of the pest to California using the criteria below.

Economic Impact: A, B, C

A. The pest could lower crop yield.

B. The pest could lower crop value (includes increasing crop production costs).

C. The pest could trigger the loss of markets (includes quarantines).

D. The pest could negatively change normal cultural practices.

E. The pest can vector, or is vectored, by another pestiferous organism.

F. The organism is injurious or poisonous to agriculturally important animals.

G. The organism can interfere with the delivery or supply of water for agricultural uses.

Economic Impact Score: 3

– Low (1) causes 0 or 1 of these impacts.

– Medium (2) causes 2 of these impacts.

– High (3) causes 3 or more of these impacts.

5) Environmental Impact: Gladiolus rust could impact home/urban garden plantings.

Evaluate the environmental impact of the pest on California using the criteria below.

Environmental Impact: E

A. The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.

B. The pest could directly affect threatened or endangered species.

C. The pest could impact threatened or endangered species by disrupting critical habitats.

D. The pest could trigger additional official or private treatment programs.

E. The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.

Environmental Impact Score: 2

– Low (1) causes none of the above to occur.

– Medium (2) causes one of the above to occur.

– High (3) causes two or more of the above to occur.

Consequences of Introduction to California for Gladiolus Rust:

Add up the total score and include it here. 12

-Low = 5-8 points

-Medium = 9-12 points

-High = 13-15 points

6) Post Entry Distribution and Survey Information: Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included.

Evaluation is ‘High’. Gladiolus Rust has spread to at least 12 California counties since its first detection in 2006. 

Score (-3). 

-Not established (0) Pest never detected in California, or known only from incursions.

-Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).

-Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.

–High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

Final Score:

7) The final score is the consequences of introduction score minus the post entry distribution and survey information score: (Score)

Final Score:  Score of Consequences of Introduction – Score of Post Entry Distribution and Survey Information = 9.

Uncertainty:

None.

Conclusion and Rating Justification:

Based on the evidence provided above the rating for the gladiolus rust pathogen, Uromyces transversalis, is proposed to continue as C.

References:

Blomquist, C. L., S. L. Thomas, J. M. Mckemy, P. A. Nolan, and M. Luque-Williams.  2007.  First report of Uromyces transversalis, causal agent of gladiolus rust, in San Diego County, California.  Plant Disease, 91: 1202.  http://dx.doi.org/10.1094/PDIS-91-9-1202C

CABI.  2017.  Uromyces transversalis (gladiolus rust) full datasheet.  Crop Protection Compendium.  http://www.cabi.org/cpc/datasheet/55868

EPPO.  2017.  Uromyces transversalis (UROMTV).  PQR database.  Paris, France: European and Mediterranean Plant Protection Organization.  https://gd.eppo.int/

Farr, D. F., and A. Y. Rossman. Fungal Databases, U.S. National Fungus Collections, ARS, USDA. Retrieved August 1, 2017, from https://nt.ars-grin.gov/fungaldatabases/

Preston, Catherine (2009) USDA Presentation: Gladiolus Rust, Balancing Eradication Efforts and Growers’ Needs through Regulation. http://dpm.ifas.ufl.edu/plant_pest_risk_assessment/ALS6921%20Presentations/PPQ_GR%20presentation.pdf

Scheck, H.  2012. Communication to Timothy Tidwell, Plant Pathologist, CDFA, from Heather Scheck, Plant Pathologist, Santa Barbara County Department of Agriculture (in 2012).

Schwartzburg, K. 2006. NPAG Report Uromyces transversalis (Thüm.) G. Winter 1884: Gladiolus Rust.

USDA, 2007. Gladiolus Rust (Uromyces transversalis): A National Management Plan for Exclusion and Eradication.  GR Plan Original, February 28, 2007.

USDA.  2015.  APHIS revives response to domestic detections of gladiolus rust caused by Uromyces transversalis.  DA-2015-20, dated May 13, 2015 to State and Territory Agricultural Regulatory Officials.

USDA APHIS PPQ.  2007.  Pest Alert.  Gladiolus rust: a new threat.  United States Department of Agriculture Animal and Plant Health Inspection Service Plant Protection and Quarantine.  APHIS 81-35-011.

USDA PCIT.  2017.  USDA Phytosanitary Certificate Issuance & Tracking System. August 1, 2017, 4:03:49 pm CDT.  https://pcit.aphis.usda.gov/PExD/faces/ReportHarmOrgs.jsp.

Responsible Party:

John J. Chitambar, Primary Plant Pathologist/Nematologist, California Department of Food and Agriculture, 3294 Meadowview Road, Sacramento, CA 95832. Phone: 916-262-1110, plant.health[@]cdfa.ca.gov.

Pest Rating: C

Posted by ls

Fungi, Plant Pathogens

Thekopsora minima P. Syd. & Syd. 1915

4 Comments
California Pest Rating for
Thekopsora minima P. Syd. & Syd. 1915
Pest Rating: C
PEST RATING PROFILE
Initiating Event:

On May 2, 2017, a shipment of blueberry (Vaccinium corymbosum) plants showing symptoms of rust were intercepted in San Francisco by San Francisco County Agricultural Officers.  The shipment had originated in Oregon and was destined to a wholesale garden store in San Francisco.  A sample of symptomatic leaves was collected by the County and sent to the CDFA Plant Pathology Lab for diagnosis.  On May 22, 2017, Suzanne Latham, CDFA plant pathologist, identified the fungal pathogen associated with the diseased leaf tissue as Thekopsora minima.  The pathogen was assigned a temporary Q rating.  Subsequently, the consequences of introduction and establishment of T. minima in California are assessed and a permanent rating is proposed herein.

History & Status:

Background: Thekopsora minima is a fungal pathogen that causes rust disease in blueberries, cranberries, rhododendrons, and other plants in the Ericaceae family.  The pathogen completes its life cycle on two different hosts (heteroecious), namely, blueberries and hemlock, and rust disease can lead to extensive defoliation of severely infected plants.

The blueberry leaf rust pathogen was first recorded as endemic in Northeastern America and Japan.  During the past decade, it was introduced on infested Vaccinium corymbosum to other countries including South Africa, Mexico, Australia and Colombia (EPPO, 2016). In the USA, it has been reported mainly from northeastern states and, more recently, from the Western Pacific states of Oregon and California (Wiseman et al., 2016; Shands et al., 2017).

Prior to 1993, taxonomically, Thekopsora minima was generally accepted as a member of a species complex known as Pucciniastrum vaccinii, which was considered the causal agent of blueberry rust.  However, Sato et al., (1993) identified three distinct rust fungi species on Vaccinium spp., of which one of them, namely, T. minina, is pathogenic on blueberry, while the other two species, Naohidemyces vaccinii (formerly P. vaccinii) and N. fujisanensis, were not regarded as pathogens of blueberry, although they infected other Vaccinium species.  Sato et al., (1993) also noted that at that time, T. minima, occurred, in eastern North America and Japan.  Nevertheless, because of the past taxonomic confusion of the species complex, the true global distribution of T. minima may be uncertain as some records attributed to Pucciniastrum vaccinii in Argentina, Hawaii (USA), and Spain may be misidentifications of T. minima (Schrader & Maier, 2015).  Thekopsora minima is also known by its synonyms: Peridermium peckii Thüm, 1880, Uredo minima Schwein, 1922, and Pucciniastrum minimum (Schwein.) Arthur 1906 (Farr & Rossman, 2017).

In California, Naohidemyces vaccinii has been reported on Vaccinium membranaceum (thin leaf huckleberry), V. caespitosum (dwarf bilberry), V. parvifolium (red huckleberry), V. ovatum (California huckleberry), and Vaccinium sp. (French, 1989).  However, recent reports from several states in the US (Oregon and Michigan), China, Mexico, and South Africa, have indicated that Thekopsora minima is the primary pathogen on northern and southern highbush blueberries (Rebollar-Alviter et al., 2011; Shilder & Miles, 2011; Wideman et al., 2016; Zheng et al., 2017).  Rust symptoms have been occasionally observed on various southern highbush blueberry cultivars (Vaccinium corymbosum) within California’s central coastal area, with particular incidences noted in Santa Barbara County in 2010 and 2006 (personal communications: Dr. Timothy D. Miles, Assistant Professor of Plant Pathology, California State University Monterey Bay, and Dr. Janet C. Broome, Global Plant Healthy Senior Manager, Driscoll’s, 2017).  Rust in blueberry was also observed in Ventura County, and has most likely been in the State since the early 2000s (personal communication: Dr. Janet C. Broome, Driscoll’s, 2017). In 2016-2017, rust symptoms, observed on several blueberry plants and cultivars in a field trials in Watsonville, Santa Cruz County, were confirmed by molecular sequencing to be caused by T. minima and marked a first published report of this pathogen in California (Shands, et al., 2017).  On August 9, 2017, in order to officially substantiate the presence of blueberry rust in California, official samples of symptomatic blueberry plant tissue were collected from infected plants in Santa Cruz and Ventura Counties, by the respective County Agricultural officials and submitted to the CDFA Plant Pathology Laboratory for identification of the associated pathogen.  Following morphological and molecular sequence analysis, Cheryl Blomquist, CDFA plant pathologist, confirmed the pathogen to be T. minima.

Disease development: Teliospores of T. minima hibernate on blueberry leaves on the ground and after germination in late spring, infest the alternate host, Tsuga spp., via basidiospores.  Aeciospores are produced and infest Vaccinium and other Ericaceae host plants resulting in the production of urediniospores.  The latter ensure disease spread within the crop during the entire growing season.  Furthermore, it has been shown that other closely related blueberry rust species are capable of surviving as mycelium in plant buds and directly producing urediniospores in spring, thereby eliminating the need of the alternate host (EPPO, 2016).  It is not known if this is the case for T. minima in California where two native host species, Tsuga heterophylla and T. mertensiana can serve as alternate hosts for the pathogen to complete its lifecycle.  These two species are also native to the Pacific western states although the fungus has not been recovered from Tsuga (Wiseman et al., 2016; Shands, et al., 2017).  The other two hemlocks that are alternate hosts, T. canadensis and T. diversifolia, are not generally cultivated in California but may be present in small areas of private production and nurseries.  Pfister et al., 2004, experimentally determined the predicted optimum temperature for urediniospores to be 19.5°C, with a 5% variation in uredinia production between 17.5 and 22°C.

Dispersal and spread: Spores of Thekospora minima are spread over short distances to nearby plants by wind and rain. Spores may also be spread by human contact, clothing, equipment and packaging.  Long distance spread occurs mainly through passage of infected plants including fruit to non-infected regions (EPPO, 2016, Tasmania, 2014).

Hosts: The uredinial and telial stages of the pathogen are found on the main hosts in Vaccinium spp., namely, V. angustifolium var. laevifolium (lowbush blueberry), V. corymbosum (highbush blueberry), V. membranaceum (deciduous huckleberry) and V. erythrocarpum (southern mountain cranberry) in the family Ericaceae.  Other hosts belong to different genera in the same family: Azalea sp., A. pontica var. daviesii, Gaylussacia sp., G. baccata (black huckleberry), Leucothoe sp., Lyonia nezikii, L. ovalifolia var. elliptica, Menziesia sp., Pernettya sp., Pieris sp., Rhododendron nudiflorum, R. ponticum, and Rhodora canadensis.  The aecial stage of the pathogen is found on the alternate host, Tsuga spp., (hemlock; Pinaceae), T. canadensis (eastern hemlock), T. diversifolia (Japanese hemlock), T. heterophylla (western hemlock), T. mertensiana (mountain hemlock) (EPPO, 2016; Farr & Rossman, 2017; Wiseman et al., 2016).

Symptoms: Initial symptoms appear as small yellow, chlorotic leaf spots on upper surfaces of young leaves. As infection progresses these lesions turn rust or brown-colored, enlarge and coalesce covering large areas of a leaf.  On the underside of leaves, small flecks surrounded by water-soaked halos develop turning into yellow-orange, powdery pustules containing uredinia with urediniospores.  Pustules may also develop on blueberry fruit.  In severe infections premature leaf drop and plant defoliation can occur and result in decline in fruit yield and flower production (EPPO, 2016).

Damage Potential: Blueberry rust disease caused by Thekopsora minima may result in plant defoliation and decline in fruit and flower production.  Generally, under conditions of high humidity required for rust fungi infection, significant losses in blueberry production and other Ericaceae host plants can be expected. However, in California, such high humidity climates are not anticipated in blueberry cultivated regions and T. minima has not caused significant rust disease in blueberry, even though it has been in the State for over 17 years ((personal communication: Dr. Janet C. Broome, Driscoll’s, 2017).  Infected plants do not suffer from leaf drop, which is generally associated with the rust, and the pathogen has not been an issue of concern for blueberry growers to warrant administration of control measures.  Some rust disease is apparent on leaves from early spring into summer following periods of significant rain, however, it is difficult to find infected plants later in the season (personal communications: Dr. Janet C. Broome, Driscoll’s, 2017 and Dr. Timothy D. Miles, CSUMB).  Similarly, economic damage to other environmental host plants is expected to be minimal as the pathogen has already been in California for several years without any significant increase of its impact.

Worldwide Distribution: Asia: China, Japan; Africa:  South Africa; Europe: Netherlands (restricted distribution), Portugal (present, few occurrences); North America: Canada, Mexico, USA; South America: Colombia; Oceania: Australia (New South Wales, Queensland, Victoria) (EPPO, 2016, 2017; Mostert et al., 2010; Zheng et al., 2017).

In Europe, the pathogen is currently regarded as “Transient, under eradication” in Belgium and Germany (EPPO, 2017).  In the USA, it has been reported from Delaware, Massachusetts, Michigan, New York and Oregon (EPPO, 2017; Sato et al., 1993; Schilder & Miles, 2011; Wiseman et al., 2016).

Official Control: Thekopsora minima has been on the EPPO Alert List for the European Union since 2016 (EPPO, 2017).  Presently, Thekoposora minima is on the ‘Harmful Organism List” for Peru (USDA PCIT, 2017).

California Distribution: Thekopsora minima has officially been detected in Santa Cruz and Ventura Counties.  The pathogen has also been reported from Santa Barbara County (Shands et al., 2017).

California Interceptions: Thekopsora minima has only been detected once in a shipment of blueberry plants intercepted in San Francisco in 2017 (see “Initiating Event”).

The risk Thekopsora minima would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: Main hosts of Thekopsora minima are in the family Ericaceae and include blueberries, rhododendrons and azaleas.  Blueberries are grown in northern coastal and southern coastal regions and in the San Joaquin Valley.  Rhododendrons, azaleas and other horticultural hosts are grown throughout California particularly in coastal climates.  However, because T. minima requires high humidity for infection and development in order to cause significant disease, it would only be likely to establish in very limited areas of the State.  The pathogen is already established in several coastal areas, for the past several years, and rust disease appears typically only during early spring to summer following significantly wet periods.

Evaluate if the pest would have suitable hosts and climate to establish in California.

Score: 1

– Low (1) Not likely to establish in California; or likely to establish in very limited areas.

– Medium (2) may be able to establish in a larger but limited part of California.

– High (3) likely to establish a widespread distribution in California.

2) Known Pest Host Range: Thekopsora minima has a moderate host range.  Main hosts of the pathogen are in the family Ericaceae and include blueberries, rhododendrons, and azaleas.

Evaluate the host range of the pest.

Score: 2

– Low (1) has a very limited host range.

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

3) Pest Dispersal Potential: Urediniospores are produced in abundance and ensure disease spread within the crop during the entire growing season. Spores are spread over short distances to nearby plants by wind and rain and may also be spread by human contact, clothing, equipment and packaging.  Long distance spread occurs mainly through passage of infected plants including fruit to non-infected regions.

Evaluate the natural and artificial dispersal potential of the pest.

Score: 3

– Low (1) does not have high reproductive or dispersal potential.

– Medium (2) has either high reproductive or dispersal potential.

– High (3) has both high reproduction and dispersal potential.

4) Economic Impact: While blueberry rust disease has been reported to cause plant defoliation, this has not been the case in California, even though the fungus has been present in the State for several years. Blueberry growers have noted that some rust disease is apparent on blueberry leaves from early spring into summer following periods of significant rain, however, it is difficult to find infected plants later in the season.  Infected plants do not suffer from leaf drop, which is generally associated with the rust, and the pathogen has not been an issue of concern for blueberry growers to warrant administration of control measures.  No yield loss due to this rust pathogen in California has been observed or reported (see; ‘Damage Potential’).

Evaluate the economic impact of the pest to California using the criteria below.

Economic Impact: None

A. The pest could lower crop yield.

B. The pest could lower crop value (includes increasing crop production costs).

C. The pest could trigger the loss of markets (includes quarantines).

D. The pest could negatively change normal cultural practices.

E. The pest can vector, or is vectored, by another pestiferous organism.

F. The organism is injurious or poisonous to agriculturally important animals.

G. The organism can interfere with the delivery or supply of water for agricultural uses.

Economic Impact Score: 1

– Low (1) causes 0 or 1 of these impacts.

– Medium (2) causes 2 of these impacts.

– High (3) causes 3 or more of these impacts.

5) Environmental Impact: Although, horticultural and environmental plants, such as azaleas and rhododendrons, are hosts of Thekopsora minima (see: ‘Hosts’), the pathogen has not increased in its spread or impact in cultivated communities over the past several years of its presence in California.  Therefore, no significant impact on the environment or home/ornamental plantings is expected.

Evaluate the environmental impact of the pest on California using the criteria below.

Environmental Impact:  None

A. The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.

B. The pest could directly affect threatened or endangered species.

C. The pest could impact threatened or endangered species by disrupting critical habitats.

D. The pest could trigger additional official or private treatment programs.

E. The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.

Environmental Impact Score: 1

– Low (1) causes none of the above to occur.

– Medium (2) causes one of the above to occur.

– High (3) causes two or more of the above to occur.

Consequences of Introduction to California for Thekopsora minima: Low (8)

Add up the total score and include it here.

–Low = 5-8 points

-Medium = 9-12 points

-High = 13-15 points

6) Post Entry Distribution and Survey Information:  Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included.

Evaluation is Low.  Thekopsora minima has officially been detected only in few coastal counties in California.

Score: (-1)

-Not established (0) Pest never detected in California, or known only from incursions.

–Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).

-Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.

-High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

Final Score:

7) The final score is the consequences of introduction score minus the post entry distribution and survey information score: (Score)

Final Score:  Score of Consequences of Introduction – Score of Post Entry Distribution and Survey Information = 7

Uncertainty:  

It is not known if the pathogen will infect hemlock (Tsuga spp.) in California, to complete its life cycle.  The pathogen was not recovered from hemlock in California and Oregon (Pacific coastal regions).  Hemlock species are widespread in California.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Thekopsora minima is C.

References:

Calflora.  2017.  Information on California plants for education, research and conservation. [web application]. 2017. Berkeley, California. The Calflora Database [a non-profit organization].  http://www.calflora.org/

EPPO.  2017.  Thekopsora minima (THEKMI).  EPPO Global Database (last updated: 2017-05-19).  https://gd.eppo.int/taxon/THEKMI/distribution.

French, A.M. 1989. California Plant Disease Host Index. California Department of Food and Agriculture, Sacramento (Updated online version by T. Tidwell, May 2, 2017).

Mostert L., W. Bester, T. Jensen, S. Coertze, A. van Hoorn, J. Le Roux, E. Retief, A. Wood, and M C. Aime.  2010.  First report of leaf rust of blueberry caused by Thekopsora minima on Vaccinium corymbosum in the Western Cape, South Africa.  Plant Disease 95: 478.

Pfister, S. E., S. Halik, and D. R. Bergdahl.  2004.  Effect of temperature on Thekopsora minima urediniospores and uredinia.  Plant disease, 88: 359-362.

Rebollar-Alviter, A., A. M. Minnis, L. J. Dixon, L. A. Castlebury, M. R. Ramirez-Mendoza, H. V. Silva-Rojas, and G. Valdovinos-Ponce.  2011.  First report of leaf rust of blueberry caused by Thekopsora minima in Mexico. Plant Disease 95: 772.

Sato, S., K. Katsuya, and Y. Hiratsuka.  1993.  Morphology, taxonomy and nomenclature of Tsuga-Ericaceae rusts.  Transactions of the Mycological Society of Japan 34: 47-62.

Schilder, A. M. C., and T. D. Miles.  2011.  First report of blueberry leaf rust caused by Thekopsora minima on Vaccinium corymbosum in Michigan.  Plant Disease, 95: 768.  https://doi.org/10.1094/PDIS-12-10-0884.

Schrader, G., and W. Maier.  2015.  Express – PRA for Thekopsora minima occurrence. Julius Kühn-Institute, Institute for Plant Health.  Translated by Elke Vogt-Amdt.  http://pflanzengesundheit.jki.bund.de/dokumente/upload/fee0d_thekopsora-minima_express-pra.pdf

Shands, A. C., T. Ho, and T. D. Miles.  2017.  First report of leaf rust on southern highbush blueberry caused by Thekopsora minima in California.  Plant Disease (Accepted for publication).

Tasmania.  2014.  Blueberry rust (Thekopsora minima P. Syd & Syd).  Biosecurity Tasmania Fact Sheet, current as at October 2014. http://www.dpipwe.tas.gov.au/biosecurity/plant-biosecurity/pests-and-diseases.

USDA PCIT.  2017.  USDA Phytosanitary Certificate Issuance & Tracking System. Retrieved May 31, 2017. 6:30:49 pm CDT.  https://pcit.aphis.usda.gov/PExD/faces/ReportHarmOrgs.jsp.

Wiseman, M. S., M. I. Gordon, M. L. Putnam.  2016.  First report of leaf rust caused by Thekopsora minima on Northern highbush blueberry in Oregon. Plant Disease 100: 1949.

Zheng, X., G. Tang, Y. Tian, X. Huang, X. Chang, H. Chen, H. Yang, S. Zhang, and G. Gong.  2017.  First report of leaf rust of blueberry caused by Thekopsora minima in China. Plant Disease 101: 835.  https://doi.org/10.1094/PDIS-09-16-1379-PDN

Responsible Party:

John J. Chitambar, Primary Plant Pathologist/Nematologist, California Department of Food and Agriculture, 3294 Meadowview Road, Sacramento, CA 95832. Phone: 916-262-1110, plant.health[@]cdfa.ca.gov.

NOTE:

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Pest Rating: C

Posted by ls

Fungi, Plant Pathogens

Ramularia salviicola Tharp

California Pest Rating  for
Ramularia salviicola Tharp
Pest Rating: C
PEST RATING PROFILE
Initiating Event:

On April 14, 2017, sage (Salvia sp.) plants showing symptoms of leaf spots were detected in a nursery in San Luis Obispo County by County Agricultural officials.  A sample of diseased leaves was sent to the CDFA Plant Pathology Laboratory for diagnosis.  On April 24, 2017, Suzanne Latham, CDFA plant pathologist, identified the fungal pathogen, Ramularia salviicola associated with the diseased leaf tissue.  The pathogen was assigned a temporary Z rating as it has been recorded earlier in California, but never assigned a rating.  Subsequently, the consequences of introduction and establishment of R. salviicola in California are assessed and a permanent rating is proposed herein.

History & Status:

Background:   Ramularia salviicola is a fungal pathogen that causes leaf spot disease in host plants.  This pathogen was first discovered on Salvia farinacea in Austin Texas (Tharp, 1915).   Since then, it has only been reported from California on black sage, hummingbird sage and an unknown sage species (French, 1989).

Hosts:  Ramularia salviicola is only known to infect Salvia spp. (sage) in the family Lamiaceae: Salvia farinacea (mealycup sage), S. mellifera (black sage), Salvia sp. (sage), S. spathacea (hummingbird sage) (Braun, 1998; Farr & Rossman, 2017).

Symptoms:  Leaf spots are produced on both sides of living leaves.  Spots are subcircular to irregular, 1-10 mm in diameter, occasionally coalescing, brown with indefinite margin or with a diffuse yellowish halo, and sometimes divide into zones (Braun, 1998).

Disease development and spread: While there is a paucity of information reported on the specific biology of Ramularia salviicola, it is likely to be similar to that of other species within the genus.  Clusters of conidiophores arise from leaf lesions (spots) producing conidia (asexual spores) on living leaves.  Conidia are airborne and are spread accordingly to nearby plants.  It is also likely that, similar to other Ramularia species causing leaf spot disease, R. salviicola is transmitted as mycelium within the integument of seed and by movement of infested soil (Daughtrey et al., 1995),

Dispersal and spread: Infected plants and nursery stock, seeds, airborne conidia (Daughtrey et al., 1995).

Damage Potential: Quantitative losses due to Ramularia salviicola have not been reported.  Reduction in photosynthetic area due to leaf spotting can be expected as well as leaf wilt, premature leaf drop, and reduced tree vigor may result.  Leaf spot damage caused by R. salviicola may significantly impact commercial production and marketing of nursery ornamental plants, as well as private productions.  Black sage and hummingbird sage are perennial shrubs that are native to California and confined mainly to the southern and central coastal counties (Calflora, 2017).  Several other species of Salvia are also cultivated throughout California, but have not yet been reported as hosts of the pathogen.

Worldwide Distribution: North America: USA (California, Texas) (Braun, 1998; Farr & Rossman, 2017).

Official Control:  No official control for Ramularia salviicola has been reported.

California Distribution:  Southern coastal counties including, San Luis Obispo County.

California Interceptions:  None.

The risk Ramularia salviicola would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: In California, Ramularia salviicola has already become established in southern coastal regions where its hosts, black sage and hummingbird sage, are mainly cultivated. While the pathogen has not been reported from other regions it is likely to establish a larger but limited part of the State.

Evaluate if the pest would have suitable hosts and climate to establish in California.

Score: 2

– Low (1) Not likely to establish in California; or likely to establish in very limited areas.

– Medium (2) may be able to establish in a larger but limited part of California.

– High (3) likely to establish a widespread distribution in California.

2) Known Pest Host Range: The pathogen has only been found on Salvia

Evaluate the host range of the pest.

Score: 1

– Low (1) has a very limited host range.

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

3) Pest Dispersal Potential: Ramularia salviicola has high reproductive and dispersal potential. The pathogen is likely to be transmitted through movement of infected plants and nursery stock, integuments of seed and airborne conidia.

Evaluate the natural and artificial dispersal potential of the pest.

Score: 3

– Low (1) does not have high reproductive or dispersal potential.

– Medium (2) has either high reproductive or dispersal potential.

– High (3) has both high reproduction and dispersal potential.

4) Economic Impact: Ramularia salviicola causes leaf spot in sage plants.  While there is no information on quantitative crop loss caused by this pathogen, leaf spot disease could lower crop value and cause loss of markets.  Use of preventive chemical sprays and other control measures could increase production costs.

Evaluate the economic impact of the pest to California using the criteria below.

Economic Impact: B, C

A. The pest could lower crop yield.

B. The pest could lower crop value (includes increasing crop production costs).

C. The pest could trigger the loss of markets (includes quarantines).

D. The pest could negatively change normal cultural practices.

E. The pest can vector, or is vectored, by another pestiferous organism.

F. The organism is injurious or poisonous to agriculturally important animals.

G. The organism can interfere with the delivery or supply of water for agricultural uses.

Economic Impact Score:  2

– Low (1) causes 0 or 1 of these impacts.

– Medium (2) causes 2 of these impacts.

– High (3) causes 3 or more of these impacts.

5) Environmental Impact:  The pathogen could significantly impact ornamental plantings in home/ urban, public gardens and other recreational environments.

Evaluate the environmental impact of the pest on California using the criteria below.

Environmental Impact: E

A. The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.

B. The pest could directly affect threatened or endangered species.

C. The pest could impact threatened or endangered species by disrupting critical habitats.

D. The pest could trigger additional official or private treatment programs.

E. The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.

Environmental Impact Score: 2

– Low (1) causes none of the above to occur.

– Medium (2) causes one of the above to occur.

– High (3) causes two or more of the above to occur.

Consequences of Introduction to California for Ramularia salviicola:  Medium (10)

Add up the total score and include it here.

-Low = 5-8 points

–Medium = 9-12 points

-High = 13-15 points

6) Post Entry Distribution and Survey Information: Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included.

Evaluation is High (-3).

Score: -1

-Not established (0) Pest never detected in California, or known only from incursions.

–Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).

-Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.

-High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

Final Score:

7) The final score is the consequences of introduction score minus the post entry distribution and survey information score: (Score)

Final Score:  Score of Consequences of Introduction – Score of Post Entry Distribution and Survey Information = 7

Uncertainty:

None.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Ramularia salviicola is C.

References:

Braun, U. 1998. A Monograph of Cercosporella, Ramularia and Allied Genera (Phytopathogenic Hyphomycetes) Vol. 2.  IHW-Verlag 2: 439.

Calflora.  2017.  Information on California plants for education, research and conservation. [web application]. 2017. Berkeley, California. The Calflora Database [a non-profit organization].  http://www.calflora.org/

Daughtery, M. L., R. L. Wick, and J. L. Peterson.  1995.  Cyclamen stunt and Ramularia leaf spot of Cyclamen and Primula.  In Compendium of Flowering Potted Plant Diseases.  APS Press, The American Phytopathological Society.  Page 20.

Farr, D. F., and A. Y. Rossman.  2017.  Fungal Databases, U. S. National Fungus Collections, ARS, USDA. Retrieved June 5, 2017, from http://nt.ars-grin.gov/fungaldatabases/

French, A.M. 1989. California Plant Disease Host Index. California Department of Food and Agriculture, Sacramento (Updated online version by T. Tidwell, May 2, 2017).

Responsible Party:

John J. Chitambar, Primary Plant Pathologist/Nematologist, California Department of Food and Agriculture, 3294 Meadowview Road, Sacramento, CA 95832. Phone: 916-262-1110, plant.health[@]cdfa.ca.gov.

NOTE:

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Pest Rating: C

Posted by ls

Fungi, Plant Pathogens

Phytophthora cambivora (Petri) Buisman 1927

6 Comments
California Pest Rating for
Phytophthora cambivora (Petri) Buisman 1927
Pest Rating: B
PEST RATING PROFILE
Initiating Event:

None.  The current risk and status of Phytophthora cambivora in California are reassessed and a permanent rating is proposed.

History & Status:

Background:  Phytophthora cambiv ora is an oomycete pathogen that can cause crown and root rot disease, usually in conjunction with other Phytophthora spp., in its hosts.  Phytophthora root and crown rot disease are among the most important soilborne diseases of stone fruits (Browne & Mircetich, 1995).  The pathogen is known to cause ink disease in chestnut.  It is widespread in temperate regions of all continents and occurs in soils of natural forests, agricultural fields, and orchards.  It can persist and spread in different environments and is capable of surviving in the soil as a saprophyte and by producing resting spores.

In California, P. cambivora has been found in several fruit and nut, forest, and native host plants, including: apple, avocado, American plum, apricot, chamise, hoary manzanita, palm, birchleaf mountain mahogany, apple avocado, American plum, apricot, sweet cherry, cherry plum, sour cherry, European plum, sweet almond, holly leaf cherry, Mahaleb cherry, peach, nectarine, Japanese plum, European/common pear, oak, canyon oak, California live oak, Japanese maple, toyon, madrone, bristlecone fir (French, 1989, CDFA Pest Damage Records).    Phytophthora diagnostic scientists have also found P. cambivora in other symptomatic (damaged) native plant species in natural stands in California.  These unpublished records of P. cambivora-infected native plants include, Ione manzanita (Arctostaphylos myrtifolia), sticky white leaf manzanita (A. viscida), pallid manzanita (A. pallida), Raiche’s manzanita (A. stanfordiana ssp. raichei), coyote ceanothus (Ceanothus ferriseae), valley oak (Quercus lobata), and California coffeeberry (Frangula californica) (comments from S. Frankel, plant pathologist, USDA Forest Service, and ‘Phytophthoras in Native Habitats Work Group’.  July, 2017).  The pathogen has also been recovered from various habitats including flowing water, stream and ditch banks, edges of roadsides and highways, forests, residential gardens, parks, cemeteries, recreational areas, and nurseries.

Saavedra et al., (2007) reported decline and mortality of golden chinquapin trees (Chrysolepis chrysophylla) in parts of northern and north-western California, similar to the damage caused by P. cambivora on the same host in Oregon.  The native range for this host species extends through the Coast Range Mountains from San Luis Obispo County, California, to Benton County, Oregon.

Recently, Jung et al., (2016) demonstrated by phylogenetic analysis that Phytophthora cambivora is a natural interspecific hybrid (a cross between two different Phytophthora species) in ITS Clade 7a, and, therefore, suggested that its name be changed to P. xcambivora.  Hybrid Phytophthora are often more aggressive than their parental species and fare better in nurseries and out-planted settings. Furthermore, P. xcambivora (= P cambivora) is the most thermo-tolerant of all species in Clade 7a, with the ability to grow at temperatures greater that 35°C.  This ability to grow at high temperatures enables the pathogen to grow in warm climates in California.

Hosts: Reported hosts of Phytophthora cambivora are present in 30 genera in 19 families: Abies bracteata (bristlecone fir), A. fraseri (fraser fir), A. procera (noble fir), Abies sp., Acer palmatum (Japanese maple), A. pennsylvanicum (striped maple), A. platanoides (Norway maple), A. rubrum (red maple), A. saccharum (sugar maple) , Acer sp., Adenostoma fasciculatum (chamise), Aesculus hippocastanum (horse chestnut), Alnus cordata (alder), A. rubra (red alder), Arbutus menziesii (madrone), Arctostaphylos canescens subsp. canescens (hoary manzanita), Areca sp. (palm),   Castanea sp. (chestnut), C. crenata (Japanese chestnut), C. dentata (American chestnut), C. mollissima (Chinese chestnut), C. pumila (allegheny chinquapin), C. sativa (chestnut), Castanea x coudercii (Couderc chestnut), Casuarina equisetifolia (casuarina), Cercocarpus betuloides (island mountain mahogany), C. montanus var. glaber (birchleaf mountain mahogany),  Chamaecyparis lawsoniana (Port Orford cedar), Chamaecyparis sp. (cypress/false cypress), Chrysanthemum cinerariifolium (pyrethrum), Chrysolepis chrysophylla (giant chinquapin), Cineraria sp., Dahlia campanulata (weeping tree dahlia), Erica sp., Eucalyptus sp. (eucalyptus), Fagus sp. (beech), F. sylvatica (common beech), Ficus carica (common fig), Heteromeles arbutifolia (toyon), Impatiens hawker (New Guinea impatiens), Juglans regia (English walnut), Juglans sp. (walnuts), Lithocarpus densiflorus (tanoak), Lobelia erinus (lobelia), Lupinus sp. (lupine), L. albus (white lupine), Malus sp. (ornamental species apple), M. domestica (apple), M. pumila var. domestica (apple), M. pumila var. dulcissima, M. sylvestris (European crab apple), Nothofagus sp. (southern beeches), Persea americana (avocado), Petunia parviflora (seaside petunia), Pieris sp., P. japonica (lily-of-the-valley shrub), Pisum sp., P. sativum (pea), Pistacia vera (pistachio), Poncirus trifoliata (hardy orange), Prunus sp., P. americana (American plum), P. amygdalus (almond), P. armeniaca (apricot), P. avium (sweet cherry), P. campanulata (Taiwan cherry), P. cerasifera (cherry plum), P. cerasus (sour cherry), P. domestica (European plum), P. dulcis (sweet almond), P. ilicifolia (hollyleaf cherry), P. mahaleb (Mahaleb cherry), P. persica (peach), P. persica var nectarina (nectarine), P. salicina (Japanese plum), Pyrus communis (European pear), P. serotina (black cherry), Quercus sp. (oak), Q. cerris (European Turkey oak) Q. agrifolia (California live oak), Q. alba (white oak), Q. chrysolepis (canyon oak), Q. macrocarpa (bur oak), Q. petraea (durmast oak), Q. ilex (holm oak), Q. robur (common oak), Q. rubra (northern red oak), Q. pubescens (downy oak), Rhododendron sp. (azalea), R. ponticum (common rhododendron), Rubus idaeus (American red raspberry), Senecio sp. (groundsel), S. cruentus, soil, Solanum tuberosum (potato), Tanacetum cinerariifolium (Pyrethrum), Taxus baccata (English yew), Ulmus sp. (elms), Vaccinium macrocarpon (cranberry), Vitis vinifera (grapevine)  (CABI, 2017; Farr & Rossman, 2017; French, 1989).

Symptoms: Phytophthora cambivora, along with other Phytophthora species, cause root and crown rot disease of walnut, cherry, apple, peach, plum, and apricot (CABI, 2017).  The expression of symptoms is dependent on the amount of root and crown tissue affected and speed of destruction.  Usually, crown rots advance rapidly and trees fall and die soon after the first warm weather of spring, while their leaves wilt, dry, and remain attached to the tree (Adaskaveg et al., 2009).  During early stages of infection, infected trees are difficult to differentiate from healthy, non-infected ones.  However, as the infection progresses, the leaves become small, chlorotic, and droopy, and grow slowly on terminal shoots.  A decline of infected trees sets in and sometimes trees without detectable symptoms die in early summer.  Collar and root rot may occur in the same tree.  Symptoms of P. cambivora often resemble those caused by other root rot or collar rot pathogens.  Collar rot is exhibited as decayed bark at the base of the trunk and can start at several points simultaneously, progressing until the lower part of the trunk is completely girdled.  Infected roots turn brown, brittle, and necrotic.  Infected root systems resulting in necrosis of lateral roots and taproots can affect top growth.  Vigorous trees with affected roots may not show appreciable crown symptoms (CABI, 2017).  Chronic infections, mainly of roots, cause reduction in growth, early senescence, and leaf fall, and may remain unthrifty for several years before succumbing to the disease.  Infected young trees are usually killed due to their small root systems and crown areas (Adaskaveg et al., 2015).

Disease development: Similar to most other Phytophthora spp., P. cambivora survives in the soil in the form of mycelium, sporangia, zoospores and oospores, and thrives in poorly-drained, water-saturated soils.  It lives as a saprophyte in litter and in soil containing dead organic material and is favored by moist and moderate climates in a wide range of pH: 3.8-7. It is not resistant to drought.  Optimum temperature range for growth is 22-24°C and maximum temperature (cessation of growth) is >32°C (CABI, 2017).  Jung et al., (2016), reported the ability for P. xcambivora (= P. cambivora) to grow at temperatures greater that 35°C.

Sporangia and zoospores of P. cambivora in humid soils are the main source of infection.  Sporangia are produced abundantly by young mycelia, which become sterile when they are more than 1 month old.  P. cambivora produces sporangia from 9 to 30°C.  Most sporangia are found on the ground surface in leaves, petals, or earthworm castings; within the upper 6 cm of soil, and near the crowns of trees (Cox, 2014).  Sporangia can germinate directly or, more commonly in P. cambivora, indirectly by producing zoospores at 9-27°C.  Zoospores allow a population to increase rapidly and disperse widely in films of free water.  Zoospores are expelled from sporangia under suitable temperature and moisture conditions and swim by means of their flagella towards their host in response to root exudates.  Once a zoospore comes in contact with a root, it germinates producing a germ tube, which penetrates the root directly under waterlogged soil conditions.   More mycelium develops, and eventually, oospores (sexual spores) are produced, and serve as resting structures that can survive for several years.  Phytophthora cambivora does not produce chlamydospores (thick-walled, asexual spores) (CABI, 2017).

Transmission: Like most Phytophthora species, P. cambivora is soil-borne and water-borne and may be spread to non-infected sites through infected plants, nursery and planting stock, and seedlings, soil, run-off and splash irrigation and rain water, and contaminated cultivation equipment, tools, and boots.  The pathogen is not seed-borne but can be spread by infected seedlings (CABI, 2017).  Irrigation water from canals, rivers, and ponds can be contaminated with Phytophthora spp. (Browne & Mircetich, 1995).

Damage Potential: Damage caused by Phytophthora cambivora alone may be difficult to assess as more than one species of Phytophthora may be associated with root and crown rot of host trees (Mircetich & Matherton, 1976).  Loss of production of apple, cherry, noble fir Christmas trees have been reported from North America (CABI, 2017).  Walnut, peach, plum and apricot are also susceptible to P. cambivora and other Phytophthora spp.  Nurseries, nursery stock and ornamental productions may be at risk and need to be monitored.

California’s native vegetation is also at risk of root and crown rot caused by P. cambivora and other Phytophthora spp., many of which are endemic (limited) to the State, while some are rare, endangered, or threatened plants, e.g., pallid manzanita, Ione manzanita, sticky white leaf manzanita, valley oak, bristlecone fir, coffeeberry, etc. (CNPS, 2017; Calflora, 2017).  Introduction of Phytophthora species are a threat to plant health in Bay Area restoration sites, where nursery stock is planted for flood control or to mitigate environmental impacts.   Detections on madrone, toyon, oaks, and manzanitas in native stands indicate that P. cambivora is capable of becoming established in a variety of native plant habitats under a range of soil and environmental conditions and can have negative impacts on native vegetation (comments from S. Frankel, plant pathologist, USDA Forest Service, and Phytophthoras in Native Habitats Work Group.  July, 2017).

Worldwide Distribution: Asia: India, Japan, Republic of Korea, Malaysia, Taiwan, Turkey; Africa: Madagascar, Mauritius, Nigeria, South Africa; North America: Canada, USA; Europe: Austria, Belgium, Croatia, Czech Republic, Denmark, France, Germany, Greece, Hungary, Ireland, Italy, Netherlands, Norway, Poland, Portugal, Romania, Russian Federation, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, United Kingdom, Yugoslavia (former); Oceania: Australia, New Zealand, Papua New Guinea (CABI, 2017).

In the USA it has been reported from Alabama, Arizona, Arkansas, California, Georgia, Maryland, Michigan, Minnesota, Missouri, Montana, New Jersey, New York, North Carolina, Ohio, Oklahoma, Oregon, Pennsylvania, South Carolina, Virginia, Washington, West Virginia (CABI, 2017).

Official Control:  Presently, Phytophthora cambivora is on the “Harmful Organism Lists” for Algeria, Canada, Chile, China, Honduras, Nicaragua, and Peru, while, Phytophthora spp. is on the “Harmful Organism Lists” for Peru and South Africa (USDA PCIT, 2017).

California Distribution: Phytophthora cambivora is widely distributed within California.  From 2013-April, 2017, the pathogen was officially detected in Alameda, Contra Costa, Marin, Monterey, Orange, Plumas, San Mateo, San Francisco, Santa Clara, Solano, and Sonoma Counties (CDFA Pest Damage Records).

California Interceptions:  None reported.

The risk Phytophthora cambivora would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: Phytophthora cambivora has already established a large distribution under moist and cool to warm climates in California.

Evaluate if the pest would have suitable hosts and climate to establish in California.

Score: 2

– Low (1) Not likely to establish in California; or likely to establish in very limited areas.

– Medium (2) may be able to establish in a larger but limited part of California.

– High (3) likely to establish a widespread distribution in California.

2) Known Pest Host Range: The pathogen has a wide host range.

Evaluate the host range of the pest.

Score: 3

– Low (1) has a very limited host range.

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

3) Pest Dispersal Potential: Phytophthora cambivora, like other Phytophthora, has high reproductive capability under moist conditions.  It is dependent on moisture for spore dissemination and plant infection.  It is soilborne and may be spread to non-infected sites through infected plants, nursery and planting stock, and seedlings, soil, run-off and splash irrigation and rain water, and contaminated cultivation equipment, tools, boots, rivers, canals, and ponds.  Therefore, it is given a high rating in this category.

Evaluate the natural and artificial dispersal potential of the pest.

Score: 3

– Low (1) does not have high reproductive or dispersal potential.

– Medium (2) has either high reproductive or dispersal potential.

– High (3) has both high reproduction and dispersal potential.

4) Economic Impact: Damage caused by Phytophthora cambivora alone may be difficult to assess as more than one species of Phytophthora may be associated with root and crown rot of host tree.  Loss in production has been reported for apple, certain stone fruit, and noble fir Christmas.  Nursery productions of agricultural and environmental host planting stock, could be at risk. Controlling the disease include soil water management and use of resistant varieties, thereby requiring changes in cultural practices and increase in crop production costs.

Evaluate the economic impact of the pest to California using the criteria below.

Economic Impact: A, B, D, G

A. The pest could lower crop yield.

B. The pest could lower crop value (includes increasing crop production costs).

C. The pest could trigger the loss of markets (includes quarantines).

D. The pest could negatively change normal cultural practices.

E. The pest can vector, or is vectored, by another pestiferous organism.

F. The organism is injurious or poisonous to agriculturally important animals.

G. The organism can interfere with the delivery or supply of water for agricultural uses.

Economic Impact Score: 3

– Low (1) causes 0 or 1 of these impacts.

– Medium (2) causes 2 of these impacts.

– High (3) causes 3 or more of these impacts.

5) Environmental Impact: In conjunction with other Phytophthora, P. cambivora may be a contributor to root and crown disease of environmental plants. California’s native vegetation is at risk of root and crown rot damage caused by P. cambivora and other Phytophthora spp., many of which are endemic (limited) to the State, while some are rare, endangered, or threatened plants.  The pathogen is capable of becoming established in a variety of native plant habitats under a range of soil and environmental conditions and can have negative impacts on native vegetation.  Also, it may significantly impact ornamental planting.

Evaluate the environmental impact of the pest on California using the criteria below.

Environmental Impact: A, B, C, E

A. The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.

B. The pest could directly affect threatened or endangered species.

C. The pest could impact threatened or endangered species by disrupting critical habitats.

D. The pest could trigger additional official or private treatment programs.

E. The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.

Environmental Impact Score: 3

– Low (1) causes none of the above to occur.

– Medium (2) causes one of the above to occur.

– High (3) causes two or more of the above to occur.

Consequences of Introduction to California for Phytophthora cambivora:

Add up the total score and include it here. 14

-Low = 5-8 points

-Medium = 9-12 points

–High = 13-15 points

6) Post Entry Distribution and Survey Information: Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included.

Evaluation is Score: (-3)

-Not established (0) Pest never detected in California, or known only from incursions.

-Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).

-Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.

–High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

 Final Score:

7) The final score is the consequences of introduction score minus the post entry distribution and survey information score: (Score)

Final Score:  Score of Consequences of Introduction – Score of Post Entry Distribution and Survey Information = 11

Uncertainty:  

None.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Phytophthora cambivora is B.

References:

Adaskaveg, J. E., J. L. Caprile, W. D. Gubler, B. L. Teviotdale.  2009.  Cherry: Phytophthora root and crown rot, pathogen: Phytophthora spp.  UCIPM Statewide Integrated Pest Management Program, University of California Agriculture & Natural Resources.  http://ipm.ucanr.edu/PMG/r105100711.html

Browne, G. T., and S. M. Mircetich.  1995.  Phytophthora root and crown rots.  In Compendium of Stone Fruit Diseases, Eds: J. M. Ogawa, E. I. Zehr, G. W. Bird, D. F. Ritchie, K. Uriu, and J. K. Uyemoto.  APS Press, The American Phytopathological Society. Pages 38-40.

CABI.  2017.  Phytophthora cambivora (root rot of forest trees) full datasheet.  Crop Protection Compendium. http://www.cabi.org/cpc/datasheet/40956

Calflora.  2017.  Information on California plants for education, research and conservation. [Web application]. 2017. Berkeley, California. The Calflora Database [a non-profit organization].  http://www.calflora.org/

CNPS.  2017.  Inventory of rare and endangered plants of California (online edition, v8-03 0.38).  California Native Plant Society, Rare Plant Program. Website http://www.rareplants.cnps.org [accessed 10 August 2017].

Cox, K.  2014.  Phytophthora collar, crown, and root rots.  In Compendium of Apple and Pear Disease and Pests Second Edition Eds: T. B. Sutton, H. S. Aldwinckle, A. M. Agnello, J. F. Walgenbach.  Pages 63-65.

Farr, D. F., and A. Y. Rossman.  2017.  Fungal Databases, U.S. National Fungus Collections, ARS, USDA. Retrieved June 9, 2017, from https://nt.ars-grin.gov/fungaldatabases/

French, A.M. 1989. California Plant Disease Host Index. California Department of Food and Agriculture, Sacramento (Updated online version by T. Tidwell, May 2, 2017).

Jung, T., M. H. Jung, B. Scanu, D. Seress, G. M. Kovács, C. Maia, A. Pérez-Aierra, T. –T. Chang, A. Chandelier, K. Heungens, K. van Poucke, P. Abad-Campos, M. Leon, S. O. Caciola, and J. Bakonyi.  2016.  Six new Phytophthora species from ITS Clade 7a including two sexually functional heterothallic hybrid species detected in natural ecosystems in Taiwan.  Persoonia 38: 100-135.

Mircetich, S. M., and M. E. Matherton.  1976.  Phytophthora root and crown rot of cherry trees.   Phytopathology 66: 549-558.

Saavedra, A., E. M. Hansen, and D. J. Goheen.  2007.  Phytophthora cambivora in Oregon and its pathogenicity to Chrysolepis chrysophylla.  Forest Pathology, 37: 409-419.

USDA PCIT.  2017.  USDA Phytosanitary Certificate Issuance & Tracking System. Retrieved June 6, 2017. 5:59:40 pm CDT.  https://pcit.aphis.usda.gov/PExD/faces/ReportHarmOrgs.jsp.

Responsible Party:

John J. Chitambar, Primary Plant Pathologist/Nematologist, California Department of Food and Agriculture, 3294 Meadowview Road, Sacramento, CA 95832. Phone: 916-262-1110, plant.health[@]cdfa.ca.gov.

NOTE:

You must be registered and logged in to post a comment.  If you have registered and have not received the registration confirmation, please contact us at plant.health[@]cdfa.ca.gov.

Comment Format:

♦  Comments should refer to the appropriate California Pest Rating Proposal Form subsection(s) being commented on, as shown below.

Example Comment:
Consequences of Introduction:  1. Climate/Host Interaction: [Your comment that relates to “Climate/Host Interaction” here.]

♦  Posted comments will not be able to be viewed immediately.

♦  Comments may not be posted if they:

Contain inappropriate language which is not germane to the pest rating proposal;

Contains defamatory, false, inaccurate, abusive, obscene, pornographic, sexually oriented, threatening, racially offensive, discriminatory or illegal material;

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♦  Comments may be edited prior to posting to ensure they are entirely germane.

♦  Posted comments shall be those which have been approved in content and posted to the website to be viewed, not just submitted.

 Pest Rating: B

Posted by ls

Fungi, Plant Pathogens

Septoria protearum Viljoen & Crous 1998

California Pest Rating for
Septoria protearum Viljoen & Crous 1998
Pest Rating: B
PEST RATING PROFILE
Initiating Event:

On March 29, 2017, lavender (Lavendula sp.) plants showing symptoms of leaf spots were detected in a nursery in San Luis Obispo County by County Agricultural officials.  A sample of diseased leaves was sent to the CDFA Plant Pathology Laboratory for diagnosis.  On May 8, 2017, Suzanne Latham, CDFA plant pathologist, identified the fungal pathogen, Septoria protearum associated with the diseased leaf tissue.  The pathogen was assigned a temporary Q rating.  Subsequently, the consequences of introduction and establishment of S. protearum in California are assessed and a permanent rating is proposed herein.

History & Status:

Background:   Septoria protearum is a fungal pathogen that causes leaf spot disease in host plants.  Septoria protearum is the asexual (anamorph) stage, for which the sexual stage or teleomorph is not known.  Verkley et al., (2013) included the pathogen S. pistaciae as a synonym of S. protearum since it could not be robustly distinguished based on a seven-gene phylogenetic analysis.  Crous et al., (2013) stated that further study and inoculation trials are needed to confirm synonymy of the two species.  Also based on DNA evidence, Verkley et al., (2013) reported multiple host family associations for S. protearum, which is unusual for other species of the genus.  Farr & Rossman (2017) included hosts of S. protearum in genera belonging to nine families. The current CDFA detection of the pathogen in lavender, increases the number of represented families to ten.  Septoria pistaciae (syn. S. protearum according to Verkley et al., 2013) was previously reported from a pistachio orchard in California (Farr et al., 1989; Michailides, 2005).

Disease development: While there is no specific information on the disease development of Septoria protearum (Michailides, 2005), it is likely to be similar to that of other species in the genus.  Generally, Septoria spp. overwinter as mycelium and as conidia (asexual spores) within pycnidia (asexual fruiting structures) on or in seed and on diseased plant debris left in the field.  Infected seeds produce infected seedlings that may result in damping-off or provide inoculum for subsequent infections.  When pycnidia in infected plant debris become wet, they swell and conidia are exuded in long tendrils and thereafter, spread by splashing rain, irrigation water, as well as contaminated tools and animals.    Septoria species usually require high moisture for infection and severe disease development, however, they can cause disease under a wide range of temperatures (10-27°C) (Agrios, 2005).  The teleomorph (sexual) stage of S. protearum is unknown.

Dispersal and spread: Infected plants and nursery stock, splashing rain, irrigation water, plant leaf debris, contact with cultivation tools and animals (Agrios, 2005).

Hosts:  Presently, all reported hosts of Septoria protearum are included in several families, viz. Aspleniaceae, Proteaceae, Rutaceae, Rosaceae, Oleaceae, Boraginaceae, Davalliaceae, Anacardiaceae, Aracaceae, and Lamiaceae.  Hosts include: Asplenium ruta-muraria (walrue fern), Boronia denticulata (mauve Boronia), Gerbera jamesonii (Gerber daisy), Geum sp. (Geum), Gevuina avellana (Avellano/Chilean hazelnut), Hedera helix (common ivy/English ivy), Ligustrum vulgare (common privet/ European privet), Masdevallia sp. (Masdevallia), Myosotis sp. (mouse’s ear), Nephrolepis sp. (fern), Pistacia vera (pistachio), Protea cynaroides (king protea), Protea sp. (protea), Skimmia sp. (Skimmia), Zantesdeschia aethiopica (calla lily) (Crous et al., 2008; Farr & Rossman, 2017; Verkley et al., 2013).  In addition, the pathogen was recently detected in Lavendula sp. (lavender; Lamiaceae) (see: ‘Initiating Event’).

Symptoms:  Leaf spots are produced in plants infected by Septoria species.  Leaf spots usually start on the lower leaves and progress upwards,  initiating as small yellowish specks that later enlarge, turn pale brown or yellowish gray, and finally dark brown.  They are usually surrounded by a narrow yellow region and may be circular to irregular.  Affected leaves may turn yellow and eventually die. Numerous small black pycnidia are aggregated and appear as dots within the leaf spots (Agrios, 2005). In pistachio, Septoria protearum produces numerous, subcuticular brown spots, 0.5-1.5 mm on both sides of the leaf, with numerous black pycnidia clustered within the spots.  In California, in pistachio fruit, the pathogen causes distinct grayish to light-brown fruit lesions, 1-4 mm in diameter, surrounded by a bright, distinctly reddish halo and usually located near the peduncle.  Leaf infections have not been observed (Michailides, 2005).

Damage Potential: Quantitative losses due to Septoria protearum have not been reported.  Photosynthetic area can be reduced due to leaf spotting.  In severe infections, leaf wilt, premature leaf drop, and reduced tree vigor may result. Leaf and fruit spots are produced in pistachio.  Leaf spot damage caused by S. protearum may significantly impact production and marketing of nursery ornamental plants.

Worldwide Distribution: Africa: South Africa; Europe: France, Germany, Italy, Netherlands, Spain, Canary Islands; North America: USA (California); Oceania:  New Zealand (Farr & Rossman, 2017).

Official Control:  No official control for Septoria protearum has been reported.  However, currently Septoria spp. is on the ‘Harmful Organism’ list for the Bolivarian Republic of Venezuela (USDA-PCIT, 2017).

California Distribution:  Previous to its current detection, Septoria protearum was reported from a pistachio orchard in California.  Its recent detection was in a nursery in San Luis Obispo County (see “Initiating Event’).

California Interceptions:  None.

The risk Septoria protearum would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: Septoria protearum has a diverse range of hosts which largely include several ornamental plant species. While the pathogen may be able to cause disease under cool and warm temperatures, it is dependent on high moisture for infection and severe disease development.  Therefore, it is likely that the pathogen may be able to establish in a larger but limited area of California.

Evaluate if the pest would have suitable hosts and climate to establish in California.

Score: 2

– Low (1) Not likely to establish in California; or likely to establish in very limited areas.

– Medium (2) may be able to establish in a larger but limited part of California.

– High (3) likely to establish a widespread distribution in California.

2) Known Pest Host Range: Presently, the pathogen has a moderate and diverse range of hosts inclusive of species in ten plant families.

Evaluate the host range of the pest.

Score: 2

– Low (1) has a very limited host range.

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

3) Pest Dispersal Potential: Septoria protearum has high reproductive potential however, dispersal of conidia from pycnidia are dependent on wet conditions from splashing rain, dew, and irrigation water. Further artificial spread is caused by use of contaminated tools, animals, etc.  Therefore, a ‘Medium’ rating is given to this category.

Evaluate the natural and artificial dispersal potential of the pest.

Score: 2

– Low (1) does not have high reproductive or dispersal potential.

– Medium (2) has either high reproductive or dispersal potential.

– High (3) has both high reproduction and dispersal potential.

4) Economic Impact: Septoria protearum causes leaf and fruit spot in host plants.  In California, it has been found in pistachio.  Other hosts include several nursery-grown ornamental plant species.  While there is no information on quantitative crop loss caused by this pathogen, leaf spot disease could lower crop value and cause loss of markets.  Use of preventive chemical sprays and other control measures could increase production costs.  Avoidance of overhead irrigations would require changes in cultural practices of irrigating plants.

Evaluate the economic impact of the pest to California using the criteria below.

Economic Impact: B, C, D

A. The pest could lower crop yield.

B. The pest could lower crop value (includes increasing crop production costs).

C. The pest could trigger the loss of markets (includes quarantines).

D. The pest could negatively change normal cultural practices.

E. The pest can vector, or is vectored, by another pestiferous organism.

F. The organism is injurious or poisonous to agriculturally important animals.

G. The organism can interfere with the delivery or supply of water for agricultural uses.

Economic Impact Score:  3

– Low (1) causes 0 or 1 of these impacts.

– Medium (2) causes 2 of these impacts.

– High (3) causes 3 or more of these impacts.

5) Environmental Impact:  The pathogen could significantly impact ornamental plantings in home/ urban, public gardens and other recreational environments.

Evaluate the environmental impact of the pest on California using the criteria below.

Environmental Impact: E

A. The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.

B. The pest could directly affect threatened or endangered species.

C. The pest could impact threatened or endangered species by disrupting critical habitats.

D. The pest could trigger additional official or private treatment programs.

E. The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.

Environmental Impact Score: 2

– Low (1) causes none of the above to occur.

– Medium (2) causes one of the above to occur.

– High (3) causes two or more of the above to occur.

Consequences of Introduction to California for Septoria protearum:  Medium (11)

Add up the total score and include it here.

-Low = 5-8 points

–Medium = 9-12 points

-High = 13-15 points

6) Post Entry Distribution and Survey Information: Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included.

Evaluation is Low.  The pathogen was originally recorded in one pistachio orchard in California (county unknown) and since then has also been found in a nursery in San Luis Obispo.  It is therefore, considered to have a localized distribution within the State.

Score: -1

-Not established (0) Pest never detected in California, or known only from incursions.

–Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).

-Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.

-High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

Final Score:

7) The final score is the consequences of introduction score minus the post entry distribution and survey information score: (Score)

Final Score:  Score of Consequences of Introduction – Score of Post Entry Distribution and Survey Information = 10

Uncertainty:  

Distribution of Septoria protearum in California is not fully known.  Treatments with suppressive fungicides may have kept its spread in check.  Also, a need for further research on taxonomic studies of the species has been mentioned in published literature.  This information, when available, may alter the proposed rating for this pathogen.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Septoria protearum is B.

References:

Agrios, G. N.  2005.  Plant Pathology (Fifth Edition).  Elsevier Academic Press, USA.  922 p.

Crous, P. W., B. A. Summerell, L. Mostert, and J. Z. Groenewald. 2008.  Host specificity and speciation of Mycosphaerella and Teratosphaeria species associated with leaf spots of Proteaceae. Persoonia 20: 59-86.

Farr, D. F., and A. Y. Rossman.  2017.  Fungal Databases, U. S. National Fungus Collections, ARS, USDA. Retrieved May 12, 2017, from http://nt.ars-grin.gov/fungaldatabases/

Farr, D. F., G. F. Bills, G. P. Chamuris, and A. Y. Rossman. 1989.  Fungi on Plants and Plant Products in the United States. APS Press. St. Paul, Minnesota.

Michailides, T. J.  2005.  Pest, disease, and physiological disorders management: above ground fungal diseases. In: Pistachio Production Manual, Eds. Beede, R. H., M. W. Freeman, D. R. Haviland, B. A. Holtz, and C. E. Kallsen, Davis, CA. Fruit and Nut Research and Information Center, Department of Plant Sciences, University of California Davis. 214–232 pp.

USDA PCIT.  2017.  USDA Phytosanitary Certificate Issuance & Tracking System. May 12, 2017, 1:43:31 pm CDT.  https://pcit.aphis.usda.gov/PExD/faces/ReportHarmOrgs.jsp.

Verkley, G. J. M., W. Quaedvlieg, H. D. Shin, and P. W. Crous.  2013.  A new approach to species delimitation in Septoria. Studies in Mycology 75: 213-305.

Responsible Party:

John J. Chitambar, Primary Plant Pathologist/Nematologist, California Department of Food and Agriculture, 3294 Meadowview Road, Sacramento, CA 95832. Phone: 916-262-1110, plant.health[@]cdfa.ca.gov.

Comment Format:

♦  Comments should refer to the appropriate California Pest Rating Proposal Form subsection(s) being commented on, as shown below.

Example Comment:
Consequences of Introduction:  1. Climate/Host Interaction: [Your comment that relates to “Climate/Host Interaction” here.]

♦  Posted comments will not be able to be viewed immediately.

♦  Comments may not be posted if they:

Contain inappropriate language which is not germane to the pest rating proposal;

Contains defamatory, false, inaccurate, abusive, obscene, pornographic, sexually oriented, threatening, racially offensive, discriminatory or illegal material;

Violates agency regulations prohibiting sexual harassment or other forms of discrimination;

Violates agency regulations prohibiting workplace violence, including threats.

♦  Comments may be edited prior to posting to ensure they are entirely germane.

♦  Posted comments shall be those which have been approved in content and posted to the website to be viewed, not just submitted.

Pest Rating: B

Posted by ls

Fungi, Plant Pathogens

Cercospora ruscicola

California Pest Rating for
Cercospora ruscicola V. G. Rao & A. S. Patil 1972
Pest Rating: B
PEST RATING PROFILE
Initiating Event:

On April 28, 2017, a shipment of Ruscus (Ruscus sp.) plants with symptoms of leaf spots and destined to a private resident in Contra Costa County, was intercepted by Contra Costa County officials.  The shipment had originated in Florida.  A sample of diseased “leaves” was sent to the CDFA Plant Pathology Laboratory for diagnosis.  On May 8, 2017, Suzanne Latham, CDFA plant pathologist, identified the fungal pathogen, Cercospora ruscicola associated with the diseased leaf tissue. As there have not been any earlier reports of this pathogen in California, it was given a temporary ‘Q’ rating.  Subsequently, the consequences of introduction and establishment of C. ruscicola in California is assessed and a permanent rating is proposed herein.

History & Status:

Background:   The fungal pathogen, Cercospora ruscicola was originally identified from necrotic lesions on “leaves” (actually, ‘cladodes’ which are leaf-like modified stems) of several Ruscus plants at Poona, India (Rao & Patil, 1972).   There have not been any further reports of the global spread of this species, however, Cercospora spp., including C. ruscicola have been detected in federally intercepted samples of Ruscus plants, according to USDA’s National Mycologist (personal communications: S. Latham, CDFA plant pathologist).  Cercospora ruscicola is not known to be present in California.  The recent detection of this species in intercepted plants from Florida marked a first record.   Cercospora ruscicola is also known by its teleomorph (sexual) stage, Mycosphaerella ruscicola A. Pande 1980.

Disease development: In general, in infected plants, Cercospora species produce conidiophores (specialized hypha) that arise from the plant surface in clusters through stomata and form conidia (asexual spores) successively.  Conidia are easily detached and blown by wind often over long distances.  On landing on surfaces of a plant host, conidia require water or heavy dew to germinate and penetrate the host.  Substomatal stroma (compact mycelial structure) may form from which conidiophores develop.  Development of the pathogen is favored by high temperatures and the disease is most destructive during summer months and warmer climates.  High relative humidity is necessary for conidial germination and plant infection.  The pathogen can overwinter in or on seed and as mycelium (stromata) in old infected leaves (Agrios, 2005).

Dispersal and spread: air-currents, infected nursery plants, infected leaves, seeds (Agrios, 2005).

Hosts:  Ruscus aculeatus (butcher’s broom), Ruscus sp. (Farr & Rossman, 2017; Rao & Patil, 1972; CDFA Pest and Damage Record, May 8, 2017).

Symptoms:  Similar to most other Cercospora diseases, symptoms caused by C. ruscicola are leaf spots.  Spots may be irregularly circular to angular, with or without a distinct border, and usually coalesce to form extensive blighted regions.  Rao and Patil (1972) observed extensive, irregular necrotic regions on leaves of Ruscus plants.

Damage Potential:  Quantitative losses due to Cercospora ruscicola have not been reported.  Photosynthetic area can be reduced due to leaf spotting.  In severe infections, leaf wilt and drop may be expected.  Rao and Patil (1972) stated that the “severe’ disease ultimately resulted in defoliation and blight of Ruscus plants in India.  Generally, the damage potential due to this pathogen is likely to be similar to other Cercospora diseases which is usually low (Agrios, 2005).

Ruscus spp. are evergreen, perennial plants that are uncommon and not grown commercially in California, even though they are able to tolerate a wide range of temperatures, except freezing, and grow in shade under wet and dry conditions (Stamp, 2001).  In California, they may be found in ornamental nurseries, and residential and public gardens where they may be at risk of infection and damage by Cercospora ruscicola.  Furthermore, Ruscus stems and berries are used in dried or fresh floral arrangements.  Damage caused by C. ruscicola may significantly impact commercial and private florist businesses.

Worldwide Distribution:  Asia: India (Farr & Rossman, 2017; Rao & Patil, 1972).

Official Control:  Presently, Cercospora ruscicola is on the ‘Harmful Organism’ list for Paraguay (USDA-PCIT, 2017).

California Distribution:  Cercospora ruscicola is not known to be established in California.

California Interceptions:  Cercospora ruscicola was detected in a single shipment of Ruscus sp. intercepted by Contra Costa County officials in April 2017 (see: ‘Initiating Event’).

The risk Cercospora ruscicola would pose to California is evaluated below.

Consequences of Introduction:   

1) Climate/Host Interaction: Ruscus are not commonly grown in California. However, they are able to grow in shade under wet and dry conditions and can tolerate a wide range of temperature (except freezing). These conditions enable the plants to grow in several areas in California and, if introduced, Cercospora ruscicola would be able to establish wherever its host plant is grown under high relative humidity/moisture and warm climate.  However, as the plants are not commercially cultivated and are uncommonly grown in residential and public gardens and ornamental nurseries, the pathogen is given a low score in this category.

Evaluate if the pest would have suitable hosts and climate to establish in California.

Score: 1

– Low (1) Not likely to establish in California; or likely to establish in very limited areas.

– Medium (2) may be able to establish in a larger but limited part of California.

– High (3) likely to establish a widespread distribution in California.

2) Known Pest Host Range: Presently, the host range is only limited to Ruscus and R. aculeatus in the family Ruscaceae.

Evaluate the host range of the pest.

Score: 1

– Low (1) has a very limited host range.

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

3) Pest Dispersal Potential: Cercospora ruscicola has high reproductive potential resulting in the successive production of conidia which are dependent on air currents, infected plants, and seed for dispersal and spread.

Evaluate the natural and artificial dispersal potential of the pest.

Score: 3

– Low (1) does not have high reproductive or dispersal potential.

– Medium (2) has either high reproductive or dispersal potential.

– High (3) has both high reproduction and dispersal potential.

4) Economic Impact: Diseased Ruscus plants exhibiting leaf spot symptoms could result in lowered value of plants and loss of markets to nurseries and florist businesses. Increased costs of production can be expected with the necessary use of appropriate fungicides and other disease management strategies.

Evaluate the economic impact of the pest to California using the criteria below.

Economic Impact: B, C

A. The pest could lower crop yield.

B. The pest could lower crop value (includes increasing crop production costs).

C. The pest could trigger the loss of markets (includes quarantines).

D. The pest could negatively change normal cultural practices.

E. The pest can vector, or is vectored, by another pestiferous organism.

F. The organism is injurious or poisonous to agriculturally important animals.

G. The organism can interfere with the delivery or supply of water for agricultural uses.

Economic Impact Score:  2

– Low (1) causes 0 or 1 of these impacts.

– Medium (2) causes 2 of these impacts.

– High (3) causes 3 or more of these impacts.

4) Environmental Impact:  The pathogen could significantly impact ornamental plantings in home/ urban, public gardens and other recreational environments.

Evaluate the environmental impact of the pest on California using the criteria below.

Environmental Impact: E

A. The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.

B. The pest could directly affect threatened or endangered species.

C. The pest could impact threatened or endangered species by disrupting critical habitats.

D. The pest could trigger additional official or private treatment programs.

E. The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.

Environmental Impact Score: 2

– Low (1) causes none of the above to occur.

– Medium (2) causes one of the above to occur.

– High (3) causes two or more of the above to occur.

Consequences of Introduction to California for Cercospora ruscicola: Medium (9)

Add up the total score and include it here.

-Low = 5-8 points

–Medium = 9-12 points

-High = 13-15 points

6) Post Entry Distribution and Survey Information: Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included.

Evaluation is ‘Not established’.

Score: 0

–Not established (0) Pest never detected in California, or known only from incursions.

-Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).

-Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.

-High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

Final Score:

7) The final score is the consequences of introduction score minus the post entry distribution and survey information score: (Score: 9)

Final Score:  Score of Consequences of Introduction – Score of Post Entry Distribution and Survey Information = 9

Uncertainty:

None.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Cercospora ruscicola is B.

References:

Agrios, G. N.  2005.  Plant Pathology (Fifth Edition).  Elsevier Academic Press, USA.  922 p.

Farr, D. F., and A. Y. Rossman.  2017.  Fungal Databases, U. S. National Fungus Collections, ARS, USDA. Retrieved May 10, 2017, from http://nt.ars-grin.gov/fungaldatabases/

Rao, V. G., and A. S. Patil.  1972.  Cercospora ruscicola sp. nov. from India.  Transactions British Mycological Society, 58: 522.

Stamp, R. H.  2001.  Florida/Holland/Israeli Ruscus production and use.  University of Florida Extension, IFAS. Circular 1268 (ENH844).

USDA PCIT.  2017.  USDA Phytosanitary Certificate Issuance & Tracking System. May 10, 2017, 12:21:55 pm CDT.  https://pcit.aphis.usda.gov/PExD/faces/ReportHarmOrgs.jsp.

Responsible Party:

John J. Chitambar, Primary Plant Pathologist/Nematologist, California Department of Food and Agriculture, 3294 Meadowview Road, Sacramento, CA 95832. Phone: 916-262-1110, plant.health[@]cdfa.ca.gov.

Comment Format:

♦  Comments should refer to the appropriate California Pest Rating Proposal Form subsection(s) being commented on, as shown below.

Example Comment:
Consequences of Introduction:  1. Climate/Host Interaction: [Your comment that relates to “Climate/Host Interaction” here.]

♦  Posted comments will not be able to be viewed immediately.

♦  Comments may not be posted if they:

Contain inappropriate language which is not germane to the pest rating proposal;

Contains defamatory, false, inaccurate, abusive, obscene, pornographic, sexually oriented, threatening, racially offensive, discriminatory or illegal material;

Violates agency regulations prohibiting sexual harassment or other forms of discrimination;

Violates agency regulations prohibiting workplace violence, including threats.

♦  Comments may be edited prior to posting to ensure they are entirely germane.

♦  Posted comments shall be those which have been approved in content and posted to the website to be viewed, not just submitted.

Pest Rating: B

Posted by ls 

Fungi, Plant Pathogens, Ratings

Stemphylium solani G. F. Weber 1930

California Pest Rating for
Stemphylium solani G. F. Weber 1930
Pest Rating: A
PEST RATING PROFILE
Initiating Event:

On March 31, 2017, the CDFA Permits and Regulations Program requested a rating for Stemphylium solani.  Therefore, the associated risk and current status of S. solani in California are assessed here and a permanent rating is proposed.

History & Status:

Background:   Stemphylium solani is a fungal pathogen that causes Gray leaf spot disease in tomato, and Stemphylium leaf blight disease in cotton, garlic, and other hosts.  Gray leaf spot in tomato is actually caused by three species of Stemphylium, one being S. solani and the other two species: S. lycopersici (Enjoji) W. Yaman (syn. S. floridanum Hannon & G. F. Weber) and S. botryosum Wallr. f. sp. lycopersici Rotem, Y. Cohen, & I. Wahl.  Gray leaf spot is regarded one of the most destructive diseases of tomato in the southeastern United States and throughout the world wherever warm and humid conditions prevail (Jones & Pernezny, 2014).

Gray leaf spot disease has been reported from several countries worldwide including the United States (see ‘Worldwide Distribution’). In the United States, the disease was first observed in 1924 and by 1928 had spread throughout Florida causing widespread defoliation. Since then, the pathogen has been reported from several states but has never been reported from California.

Disease development:  The disease begins in infested seedbeds and transplant houses or field-transplanted seedlings, usually when the plants are in the first true-leaf stage of growth.  Cotyledons are not severely infected.   The pathogen is spread when infected seedlings are transplanted to fields.  Conidia (asexual spores) can be spread over extensive distances by wind. The teleomorph or sexual stage of S. solani is not known.  The disease is favored by warm temperatures (24-27°C) and high humidity. Spore germination and infection of plant are dependent on the presence of free moisture (dew or rain) (Jones & Pernezny, 2014).  Leaf wetness is considered more important than temperature in establishment of infection (Cerkauskas, 2005).  Stemphylium solani survives as a saprophyte on infected plant debris or on volunteer tomato, pepper, gladiolus, blue lupine, and other wild solanaceous plants.  In the southern state climates, the pathogen remains viable on tomato plants which are grown throughout the year (Jones & Pernezny, 2014).  The pathogen can be seedborne (Koike et al., 2007).

Dispersal and spread: Infected plants, seedlings, and plant debris.  Conidia may be wind-blown over extensive areas or by splashing water (Jones & Pernezny, 2014).

Hosts: Hosts of Stemphylium solani are included primarily in the plant family Solanaceae.  Numerous other plant families are also included with their associated hosts, including Amaryllidaceae (Allium sp.), Asteraceae (Lactuca sp.), and Malvaceae (Gossypium hirsutum).  Hosts include, Aegiceras corniculatum (black mangrove), Allium sativum (garlic), Aster sp. (aster), Basella rubra (Malabar spinach), Capsicum annuum (bell pepper), C. annuum var. annuum (cayenne pepper), C. frutescens (chili pepper), Carthamus sp. (distaff thistles), Cirsium sp. (thistle), Citrus sp. (citrus), Convolvulus arvensis (field bindweed), Cucumis sativus (cucumber), Dactylis glomerata (orchardgrass), Dianthus caryophyllus (carnation), Gossypium hirsutum (upland cotton), Ipomoea reptans (synonym: I. aquatica, swamp morning-glory), Kalanchoe blossfeldiana (flaming katy), Lactuca sativa (lettuce), Lupinus angustifolius (narrowleaf lupine), Lupinus sp. (lupine), Lycopersicon esculentum (synonym: L. lycopersicum, tomato), Lycopersicon sp., Pelargonium zonale (horse-shoe pelargonium), Physalis pubescens (husk tomato), Physalis sp. (groundcherry), Solanum gilo (gilo), S. lycocarpum (wolf apple), S. lycopersicum (garden tomato), S. melongena (aubergine/eggplant), S. melongena var. esculentum, S. pseudocapsicum (Jerusalem cherry), S. tuberosum (potato), Vicia faba (fava bean), Vigna sinensis (synonym: V. unguiculata, cowpea) (CABI, 2017; Farr & Rossman, 2017).

Symptoms:  Gray leaf spots or lesions are almost entirely limited to the leaf blades, but under favorable conditions, lesions may develop on petioles and on the more tender parts of growing stems.  Lesions on stems are linear and parallel to the stem.  Fruit symptoms have not been observed.  In infected tomatoes, symptoms of gray leaf spot are first exhibited as minute brownish-black specks on the lower leaves.  Randomly scattered circular to oblong spots develop on adaxial and abaxial leaf surfaces without being restricted by leaf veins.  The spots may be surrounded by a narrow yellow halo and enlarge to about 2.1 mm in diameter while individual spots on the base of leaves may enlarge to twice that size or more in diameter and occasionally coalesce, thereby, killing large portions of the leaf blade. As the spots enlarge, the centers turn gray, eventually dry, crack, and fall out.  Frequently, at this stage entire leaves conspicuously turn yellow, especially if the infection is severe, and die rapidly, turning brown before dropping from the plants.  Seedbed infections result in marked defoliation without conspicuous yellowing (Jones & Pernezny, 2014; Damicone & Brandenberger, 2015).  In garlic, early symptoms of S. solani infection were observed as white spots (1-3 mm), which enlarged to sunken purple lesions, extending until the leaves withered (Zheng et al., 2008).

Damage Potential:  Gray leaf spot almost entirely affects leaves, and defoliation can be severe reducing available photosynthetic areas of infected plants thereby, resulting in reductions in plant development, quality, and fruit yields.  In China, garlic leaf blight caused by Stemphylium solani affected over 7,000 ha of field production and reduced yields up to 70% (Zheng et al., 2010).  During 1994 and 1995, a severe epidemic of leaf blight of cotton in Brazil resulted in yield losses up to 100% in some commercial fields (Mehta, 1998). Gray leaf spot disease limited tomato production in Venezuela and Malaysia (Cadeño & Carrero, 1997; Nasehi et al., 2012).   In California, processing tomatoes are grown in the warm and dry San Joaquin and Sacramento Valleys while fresh-market tomatoes are grown in the San Joaquin Valley, Central Valley, Central and Southern Coastal regions and the Imperial Valley.  It is less likely that S. solani will be able establish under warm and dry regions of the state’s tomato production acreages, as well as under the possible use of resistant varieties, protectant fungicides and cultural management strategies.  However, for tomato and other host plants under wet and warm climates, the pathogen may be able to establish within those regions.

Worldwide Distribution: Asia: Brunei Darussalam, China, Hong, Kong, Taiwan, Thailand, Korea, Malaysia; Africa: Libya, Mauritius, Senegal, Sudan, Tanzania; Europe: Greece, Spain; North America: Canada, USA (Alabama, Florida, Georgia, Indiana, Louisiana, Maryland, Mississippi, North Carolina, New Jersey, South Carolina, Tennessee, Texas, Virginia); South America: Brazil, Honduras, Venezuela; Central America and Caribbean: Cuba; Oceania: American Samoa (CABI, 2017; Cadeño & Carrero, 1997; Farr & Rossman, 2017).

Official Control: Presently, Stemphylium solani is on the Harmful Organisms list for Peru (USDA-PCIT, 2017).

California Distribution: Stemphylium solani has not been reported from California.

California Interceptions: None reported.

The risk Stemphylium solani would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: Although Stemphylium solani has a wide host range that includes several economically important agricultural crops in California as well as wild solanaceous plants, the pathogen is dependent on leaf wetness for plant infection and additionally on warm temperatures for disease development.  The disease is most severe under humid and overcast climate conditions that favor wet foliage mainly due to dew or rain.  These conditions would allow the pathogen to establish in a larger but limited part of California.

Evaluate if the pest would have suitable hosts and climate to establish in California.

Score: 2

– Low (1) Not likely to establish in California; or likely to establish in very limited areas.

– Medium (2) may be able to establish in a larger but limited part of California.

– High (3) likely to establish a widespread distribution in California.

2) Known Pest Host Range: Stemphylium solani has a wide host range of plants included primarily in the family Solanaceae. However, numerous other plant families are also included with their associated hosts.  Economically important crops include tomato, pepper, cotton, citrus, cucumber, lettuce, garlic, eggplant and others.  Several wild solanaceous host plants could allow build-up of fungal inoculum.

Evaluate the host range of the pest.

Score: 3

– Low (1) has a very limited host range.

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

3) Pest Dispersal Potential: Conidia are produced in abundance and readily dispersed by wind and splashing water. Also, the pathogen is spread through infected plants, seedlings, plant debris, and seed.

Evaluate the natural and artificial dispersal potential of the pest.

Score: 3

– Low (1) does not have high reproductive or dispersal potential.

– Medium (2) has either high reproductive or dispersal potential.

– High (3) has both high reproduction and dispersal potential.

4) Economic Impact: Stemphylium solani causes gray leaf spot in tomato and peppers as well as leaf blight in other hosts. Leaves are almost always entirely affected by the disease and defoliation can be severe reducing available photosynthetic areas of plants thereby, resulting in reductions in plant development, quality, and fruit yields.  If not controlled, significant reductions in crop yield and markets could occur.  Use of fungicides and cultural management practices could increase costs of crop production.

Evaluate the economic impact of the pest to California using the criteria below.

Economic Impact: A, B, C, D

A. The pest could lower crop yield.

B. The pest could lower crop value (includes increasing crop production costs).

C. The pest could trigger the loss of markets (includes quarantines).

D. The pest could negatively change normal cultural practices.

E. The pest can vector, or is vectored, by another pestiferous organism.

F. The organism is injurious or poisonous to agriculturally important animals.

G. The organism can interfere with the delivery or supply of water for agricultural uses.

Economic Impact Score: 3

– Low (1) causes 0 or 1 of these impacts.

– Medium (2) causes 2 of these impacts.

– High (3) causes 3 or more of these impacts.

5) Environmental Impact:  The pathogen could significantly affect home/urban gardening of agricultural crops and ornamental hosts.

Evaluate the environmental impact of the pest on California using the criteria below.

Environmental Impact: E

A. The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.

B. The pest could directly affect threatened or endangered species.

C. The pest could impact threatened or endangered species by disrupting critical habitats.

D. The pest could trigger additional official or private treatment programs.

E. The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.

Environmental Impact Score: 2

– Low (1) causes none of the above to occur.

– Medium (2) causes one of the above to occur.

– High (3) causes two or more of the above to occur.

Consequences of Introduction to California for Stemphylium solani: High (13)

Add up the total score and include it here.

-Low = 5-8 points

-Medium = 9-12 points

–High = 13-15 points

6) Post Entry Distribution and Survey Information: Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included.

Evaluation is ‘Not established’ in California.

Score: (0)

–Not established (0) Pest never detected in California, or known only from incursions.

-Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).

-Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.

-High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

Final Score:

7) The final score is the consequences of introduction score minus the post entry distribution and survey information score: (Score)

Final Score:  Score of Consequences of Introduction – Score of Post Entry Distribution and Survey Information = 13

Uncertainty:  

None.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Stemphylium, solani is A.

References:

CABI, 2017.  Stemphylium solani (gray leaf spot) basic datasheet.  Crop Protection Compendium. http://www.cabi.org/cpc/datasheet/51531

Cerkauskas, R.  2005.  Tomato diseases, Gray leaf spot, Stemphylium solani, S. lycopersici found worldwide in warm climates.  AVRDC – The World Vegetable Center Fact Sheet.  AVRDC Publication 05-634.

Cadeño, L., and C. Carrero.  1997.  First report of tomato gray leaf spot caused by Stemphylium solani in the Andes Region of Venezuela.  Plant Disease 81: 1332. http://dx.doi.org/10.1094/PDIS.1997.81.11.1332B

Damicone, J. P., and L. Brandenberger.  2015.  Common diseases of tomatoes Part 1.  Diseases caused by fungi.  Oklahoma Cooperative Extension Service EPP-7625.

Farr, D. F., and A. Y. Rossman.  2017.  Fungal Databases, U. S. National Fungus Collections, ARS, USDA. Retrieved April 3, 2017, from http://nt.ars-grin.gov/fungaldatabases/

Jones, J. P., and K. L. Pernezny.  2014.  Gray Leaf Spot.  In Compendium of Tomato Disease and Pests Second Edition.  Ed. J. B. Jones, T. A. Zitter, T. M. Momol, and S. A. Miller, APS Press. The American Phytopathological Society.  29-30 p.

Koike, S. T., P. Gladders, and A. O. Paulus.  2007.  Stemphylium solani, S. lycopersici – gray leaf spot.  In Vegetables diseases a color handbook.  Academic Press, an imprint of Elsevier, Burlington, San Diego.  211-212 p.

Mehta, Y. R.  1998.  Severe outbreak of Stemphylium leaf blight, a new disease of cotton in Brazil. Plant Disease, 82: 333-336.

Nasehi, A., J. B. Kadir, M. A. Zainal Abidin, M. Y. Wong, and F. Mahmodi.  First report of tomato gray leaf spot disease caused by Stemphylium solani in Malaysia.  Plant Disease 96: 1226.  http://dx.doi.org/10.1094/PDIS-03-12-0223-PDN

USDA PCIT.  2017.  USDA Phytosanitary Certificate Issuance & Tracking System. April 3, 2017, 1:17:10 pm CDT.  https://pcit.aphis.usda.gov/PExD/faces/ReportHarmOrgs.jsp.

Zheng, L., J. B. HUANG, and T. HSIANG.  2008.  First report of leaf blight of garlic (Allium sativum) caused by Stemphylium solani in China. Plant Pathology 57: 380.

Zheng, L., L. V. Rujing, J. Huang, D. Jiang, X. Liu, and T. Hsiang.  2010.  Integrated control of garlic leaf blight caused by Stemphylium solani in China.  Canadian Journal of Plant Pathology 32: 135-145.

Responsible Party:

John J. Chitambar, Primary Plant Pathologist/Nematologist, California Department of Food and Agriculture, 3294 Meadowview Road, Sacramento, CA 95832. Phone: 916-262-1110, plant.health[@]cdfa.ca.gov.

Comment Format:

♦  Comments should refer to the appropriate California Pest Rating Proposal Form subsection(s) being commented on, as shown below.

Example Comment:
Consequences of Introduction:  1. Climate/Host Interaction: [Your comment that relates to “Climate/Host Interaction” here.]

♦  Posted comments will not be able to be viewed immediately.

♦  Comments may not be posted if they:

Contain inappropriate language which is not germane to the pest rating proposal;

Contains defamatory, false, inaccurate, abusive, obscene, pornographic, sexually oriented, threatening, racially offensive, discriminatory or illegal material;

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♦  Comments may be edited prior to posting to ensure they are entirely germane.

♦  Posted comments shall be those which have been approved in content and posted to the website to be viewed, not just submitted.

Pest Rating: A

Posted by ls

Fungi, Plant Pathogens

Diaporthe vaccinii Shear 1931

California Pest Rating for
Diaporthe vaccinii Shear 1931
Pest Rating: C
PEST RATING PROFILE
Initiating Event:

On February 3, 2017, CDFA was requested by the USDA APHIS for information on the export of Vaccinium plants from California to the EU, in preparation of a federal risk assessment of the introduction of a quarantine fungal pathogen, Diaporthe vaccinii into the EU through USA-originated Vaccinium spp.  Subsequently, the status and risk of this pathogen in California is assessed here and a permanent rating is proposed. 

History & Status:

Background:  Diaporthe vaccinii is also known by its asexual/anamorph name, Phomopsis vaccinii, and causes stem cankers, twig blight, leafspots, and fruit rot of Vaccinium spp. (blueberries and cranberries) (EFSA, 2014).  While D. vaccinii is considered the prominent species of Diaporthe on Vaccinium spp. worldwide, there are other species within Diaporthe and Phomopsis that attack Vaccinium spp. causing diseases that include stem cankers, twig blight, and fruit rot similar to D. vaccinii  (EFSA, 2014).  Also, as symptomless (latent) infections of D. vaccinii may occur, diagnosis of the disease based on symptoms alone is not reliable but can be obtained through molecular analysis.

Diaporthe vaccinii is regarded as native to North America and has been reported from Vaccinium-growing regions in the USA and Canada (Lombard et al., 2014). During the 1960-70s twig blight disease of blueberries became a serious problem in blueberry-growing regions of Wisconsin, Indiana, and southern Michigan, and in the 1980-90s increased tremendously in prevalence and severity in the southeastern USA, particularly North Carolina (Milholland, 1995).  However, D. vaccinii is not known to be present in California and Vaccinium spp. originating in California and shipped under certification to international trading partners, continue to test free of the pathogen by CDFA (Heaton, 2017).

In California, blueberry production has been increasing over the past decade.  Blueberry cultivation is done mostly in cool northern coastal regions, however, southern cultivars with low chilling-hour requirements needed to break dormancy are also farmed in the San Joaquin Valley and southern coastal regions Bremer et al., (2008).  In 2015, blueberries were cultivated on 5,700 harvested acres in California yielding a production of 624,000 cwt for a total value of $116,979 (CASR, 2015-2016).

Disease Development:  The epidemiology of the fungus has been studied in the USA.  The pathogen overwinters in infected and dead twigs, and possibly on plant debris (fallen twigs, leaves and fruits).  Ascospores and conidia are disseminated in the crop under wet and humid conditions.  In North Carolina, rain-dispersed conidia of the anamorph Phomopsis vaccinii have been trapped throughout the growing season with the largest numbers trapped between blossom budbreak to bloom (EPPOa, 2016; Milholland, 1982).

The pathogen enter host tissues mainly through wounds and to a lesser extent directly into the tips of young, succulent shoots,  Healthy unwounded blueberry plants were not infected even after one month of exposure to natural field inoculum (EFSA, 2014). Once the fungus enters the stem through the vascular tissue, it progresses downwards towards the base, girdling the old branches at their junction and killing the part of the plant above the girdle (CABI, 2017).  The fungus also enters host vascular tissues through open flower buds and, it is believed that blueberry blight develops primarily from infection of flower buds at budbreak through bloom in North Carolina (Milholland, 1982).   Conidia on germination enter berries throughout the growing season and remain dormant until maturation causing soft rot and leakage of juice at harvest (Milholland & Daykin, 1983).  Diaporthe vaccinii has been reported to be an endophyte of apparently healthy blueberry and cranberry stems (CABI, 2017).

Germ tubes of germinating conidia enter leaves producing spots.  About 2-3 weeks later, pycnidia with conidia are apparent on stems and leaf spots.  The pathogen has been isolated from fruiting bodies found on overwintered cranberry leaves in New Jersey, but not  in Wisconsin from vines collected in the spring from beds in which dieback had been very severe in the late summer of the preceding year (Friend & Boone, 1968).  Overwintering was indicated to be necessary for ascocarp (sexual fruiting body) development, completing the life cycle, perpetuating the species, and producing a source of inoculum for infection in the next season.  However, in the southeastern USA, the pathogen is reported to overwinter in infected blueberry twigs and produce conidia from pycnidia (asexual fruiting body) in the following year (EFSA, 2014).  A correlation has also been indicated between vine dieback and dry conditions, with the latter predisposing the plant to dieback (Friend & Boone, 1968).

The pathogen grows well in a wide temperature range of 4-32°C and optimum pH 5-6.  In experiments, the most favorable temperature range for conidium germination and growth was 21-24°C wherein 95% conidia germinated and either entered plants through wounds or directly at the tips of young succulent blueberry shoots held inside a damp chamber.  About 71% shoots became blighted four days after inoculation. In artificially inoculated plants, the fungus caused cankers and dieback symptoms above 30°C (Weingartner and Klos, 1975).

Dispersal and spread: Long distance dispersal occurs through movement of infected plant vines (EPPOa, 2016). Other modes for spread include infected plant debris, leaves, twigs, and fruit, rain/irrigation water splash.

Hosts: Principal hosts include Vaccinium macrocarpon (cranberry), V. oxycoccos (small cranberry), V. oxycoccos var. intermedium (Americana and European cranberries), V. corymbosum (highbush blueberry), V. ashei (rabbiteye blueberry).  While D. vaccinii is restricted to Vaccinium species, the wild European species, V. oxycoccos which usually occurs in mountain bogs could be a reservoir host for the pathogen (EPPOa, 2016).  Other hosts are Gaultheria shallon (salal), Rhododendron sp. (Farr & Rossman, 2017).

Symptoms:  In North Carolina, the predominant symptom was blighting in one-year-old susceptible blueberry cultivars. Systemic invasion has also been reported (Milholland, 1982).  Infected succulent, current-year shoots wilt in 4 days and are covered with minute lesions.  Major branches and frequently entire plants are killed as the fungus continues to travel downwards through the stem at an average rate of 5.5 cm in 2 months.  Regardless of the stem, cankers are long and narrow and are covered by the bark or epidermis.  On blueberry stems over two-years-old, a brown discoloration of the stem xylem below wilt symptoms can be observed.  However, inoculated stems only produce localized lesions.  Infected leaves develop spots which enlarge to 1 cm with pycnidia/conidiomata appearing in two weeks.  The pathogen may remain dormant until favorable conditions allow it to continue growing.  Infection of crowns frequently end in the death of stem originating from the crown.  Infected fruits turn reddish-brown, soft, mushy, often split and leak juice at harvest (CABI, 2017; EPPOa, 2016).  The fungus penetrated blueberry fruit at all stages of development and remains latent until maturation (Milholland and Daykin, 1983).

In cranberry, Diaporthe vaccinii does not cause twig blight disease similar to blueberry, but occurs on shoots and leaves without causing significant damage (CABI, 2017).  It is also a storage rot pathogen of cranberries, mainly causing a viscid rot of fruit, which becomes soft and discolored.  Also, infected upright stems turn yellow then orange and brown before dying back (Milholland, 1995).

It is important to note that in blueberry, symptoms similar to twig blight disease can be caused by other fungal pathogens such as Godronia cassandrae, Colletotrichum spp., Fusarium spp., and Botryosphaeria dothidea.  In cranberry, upright dieback is also caused by the fungus, Synchronoblastia crypta (EPPOc, 2009; CABI, 2017).

Damage Potential:    Fruit loss of two to three pints per bush with twig blight of blueberry disease were reported in North Carolina (Milholland, 1982).  Fruit loss of 0.5% out of 15.2% defective fruit were accredited to D. vaccinii (Milholland & Daykin, 1983).  The pathogen is not considered to cause appreciable economic loss in cranberry, except in Massachusetts.  Fruit loss has been considered minor due to D. vaccinii, being attributed more to the presence of other accompanying pathogens than to D. vaccinii (CABI, 2017).

Worldwide Distribution: Asia: China; Europe: Latvia (present with restricted distribution); North America: Canada, USA; South America: Chile (CABI, 2017; Farr & Rossman, 2017; EPPOa, 2016).   The pathogen was eradicated or no longer present in most of the EU (EPPOa, 2016).  In the USA, it has been found in Arkansas, Illinois, Indiana, Maine, Maryland, Massachusetts, Michigan, New Jersey, North Carolina, Oregon, Washington, and Wisconsin.

Official Control: Diaporthe vaccinii is listed as a quarantine pest for the European Union (EPPOb, 2016).  The pathogen is on the ‘Harmful Organism’ lists for Argentina, China, Ecuador, Guatemala, India, Israel, Mexico, Morocco, New Zealand, Norway, Peru, and Taiwan (USDA PCIT, 2017).

California Distribution: Diaporthe vaccinii is not known to be established in California.

California Interceptions: None.

The risk Diaporthe vaccinii would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: Blueberry is the main host for Diaporthe vaccinii in California.  Blueberries are grown in northern coastal and southern coastal regions and in the San Joaquin Valley.  The pathogen grows well within a wide temperature range (4-32°C) and requires wet and humid conditions for spore dispersal and germination and fungal growth. Humid conditions along the coast may be more conducive for the pathogen than the drier environments of the San Joaquin Valley.  A ‘Medium’ score is given for climate-host interaction.

Evaluate if the pest would have suitable hosts and climate to establish in California.

Score: 2

– Low (1) Not likely to establish in California; or likely to establish in very limited areas.

– Medium (2) may be able to establish in a larger but limited part of California.

– High (3) likely to establish a widespread distribution in California.

2) Known Pest Host Range: Vaccinium are the main host for Diaporthe vaccinii.

Evaluate the host range of the pest.

Score: 1

– Low (1) has a very limited host range.

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

3) Pest Dispersal Potential: The pathogen has high reproductive capability resulting in production of numerous ascospores, and conidia, however, these are primarily dependent on water splash for dispersal. Long distance spread occurs primarily through movement of infected plants. A ‘Medium’ rating is given to this category.

Evaluate the natural and artificial dispersal potential of the pest.

Score: 2

– Low (1) does not have high reproductive or dispersal potential.

– Medium (2) has either high reproductive or dispersal potential.

– High (3) has both high reproduction and dispersal potential.

4) Economic Impact: Under suitable environmental conditions, Diaporthe vaccinii may infect blueberries causing storage rot of mature fruit causing significant losses in crop yield, value and market.

Evaluate the economic impact of the pest to California using the criteria below.

Economic Impact: A, B, C

A. The pest could lower crop yield.

B. The pest could lower crop value (includes increasing crop production costs).

C. The pest could trigger the loss of markets (includes quarantines).

D. The pest could negatively change normal cultural practices.

E. The pest can vector, or is vectored, by another pestiferous organism.

F. The organism is injurious or poisonous to agriculturally important animals.

G. The organism can interfere with the delivery or supply of water for agricultural uses.

Economic Impact Score: 3

– Low (1) causes 0 or 1 of these impacts.

– Medium (2) causes 2 of these impacts.

– High (3) causes 3 or more of these impacts.

4) Environmental Impact: No significant impact on the environment is expected.

Evaluate the environmental impact of the pest on California using the criteria below.

Environmental Impact:  None

A. The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.

B. The pest could directly affect threatened or endangered species.

C. The pest could impact threatened or endangered species by disrupting critical habitats.

D. The pest could trigger additional official or private treatment programs.

E. The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.

Environmental Impact Score: 1

– Low (1) causes none of the above to occur.

– Medium (2) causes one of the above to occur.

– High (3) causes two or more of the above to occur.

Consequences of Introduction to California for Diaporthe vaccinii: Low (9)

Add up the total score and include it here.

-Low = 5-8 points

–Medium = 9-12 points

-High = 13-15 points

6) Post Entry Distribution and Survey Information: Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included.

Evaluation is ‘Not established’ (0).

Score: (0)

–Not established (0) Pest never detected in California, or known only from incursions.

-Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).

-Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.

-High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

Final Score:

7) The final score is the consequences of introduction score minus the post entry distribution and survey information score: (Score)

Final Score:  Score of Consequences of Introduction – Score of Post Entry Distribution and Survey Information = 9

Uncertainty:  

None.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Diaporthe vaccinii is C.

References:

Bremer, V., G, Crisosto, R. Molinar, M. Jimenez, S. Dollahite, and C. H. Crisosto.  2008.  San Joaquin Valley blueberries evaluated for quality attributes.  California Agriculture, 62 (3): 91-96.  http://CaliforniaAgriculture.ucop.edu

CABI.  2017.  Phomopsis vaccinii (Phomopsis twig blight of blueberry) full datasheet.  Crop Protection Compendium.  http://www.cabi.org/cpc/datasheet/18747

CASR.  2015-2016. California agricultural statistics review 2015-2016.  California Department of Food and Agriculture.  https://www.cdfa.ca.gov/Statistics/PDFs/2016Report.pdf

EFSA.  2014.  Scientific opinion on the pest categorization of Diaporthe vaccinii Shear.  European Food Safety Authority (EFSA), Parma, Italy.  EFSA Journal 12: 3774.

EPPOa.  2016.  Diaporthe vaccinii data sheets on quarantine pests.  Prepared by CABI and EPPO for the EU under contract 90/399003.   https://www.eppo.int/QUARANTINE/data_sheets/fungi/DIAPVA_ds.pdf

EPPOb.  2016.  EPPO A2 list of pests recommended for regulation as quarantine pests (version 2016-09).  https://www.eppo.int/QUARANTINE/listA2.htm

EPPOc.  2009.  Diaporthe vaccinii Diagnostics.  OEPP/EPPO Bulletin 39, 18-24.

Farr, D. F., and A. Y. Rossman.  2017.  Fungal Databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved March 13, 2017, from http://nt.ars-grin.gov/fungaldatabases/

Friend, R. J., and D. M. Boone.  1968.  Diaporthe vaccinii associated with dieback of cranberry in Wisconsin. Plant Disease Reporter, 52:341-344.

Heaton, J.  2017.  J. Heaton, CDFA, email to D. Schnabel, cc: T. Walber and J. Chitambar, CDFA, sent Friday, March 10, 2017 9:01:02 am.

Lombard, L., G. C. M. Van Leeuwen, V. Guarnaccia, G. Polizzi, P. C. J. Van Rijswick, K. C. H. M. Rosendahl, J. Gabler, and P. W. Crous.  2014.  Diaporthe species associated with Vaccinium, with specific reference to Europe.  Phytopathologia Mediterranea 53: 85-97.

Milholland, R. D.  1982.  Blueberry twig blight caused by Phomopsis vaccinii. Plant Disease, 66:1034-1036.

Milholland R. D. 1995.  Phomopsis twig blight and fruit rot.  In Compendium of Blueberry and Cranberry Diseases.  APS Press, The American Phytopathological Society, pg. 13-14.

Milholland, R. D., and M. E. Daykin.  1983.  Blueberry fruit rot caused by Phomopsis vaccinii.  Plant Disease 67: 325-326.

USDA PCIT.  2017.  USDA Phytosanitary Certificate Issuance & Tracking System. Retrieved March 13, 2017. 6:04:39 pm CDT.  https://pcit.aphis.usda.gov/PExD/faces/ReportHarmOrgs.jsp.

Weingartner, D. P., and E. J. Klos.  1975.  Etiology and symptomatology of canker and dieback diseases on highbush blueberries caused by Godronia (Fusicoccum) cassandrae and Diaporthe (Phomopsis) vaccinii. Phytopathology, 65(2):105-110

Responsible Party:

John J. Chitambar, Primary Plant Pathologist/Nematologist, California Department of Food and Agriculture, 3294 Meadowview Road, Sacramento, CA 95832. Phone: 916-262-1110, plant.health[@]cdfa.ca.gov.

Comment Format:

♦  Comments should refer to the appropriate California Pest Rating Proposal Form subsection(s) being commented on, as shown below.

Example Comment:
Consequences of Introduction:  1. Climate/Host Interaction: [Your comment that relates to “Climate/Host Interaction” here.]

♦  Posted comments will not be able to be viewed immediately.

♦  Comments may not be posted if they:

Contain inappropriate language which is not germane to the pest rating proposal;

Contains defamatory, false, inaccurate, abusive, obscene, pornographic, sexually oriented, threatening, racially offensive, discriminatory or illegal material;

Violates agency regulations prohibiting sexual harassment or other forms of discrimination;

Violates agency regulations prohibiting workplace violence, including threats.

♦  Comments may be edited prior to posting to ensure they are entirely germane.

♦  Posted comments shall be those which have been approved in content and posted to the website to be viewed, not just submitted.

Pest Rating: C

Posted by ls

Fungi, Plant Pathogens

Ganoderma adspersum (Schulzer) Donk

 California Pest Rating for
Ganoderma adspersum (Schulzer) Donk
Pest Rating: B
PEST RATING PROFILE
Initiating Event:

On January 25, 2017, Dr. David Rizzo, Professor, Department of Plant Pathology, University of California, Davis, notified CDFA of his detection of Ganoderma adspersum in almond orchards in the San Joaquin Valley, during surveys which initiated during fall 2015, of almond trees for wood decay fungi. The fungus was noted to be very aggressive and had killed relatively young almond trees in some orchards.  Consequently, CDFA will collect official samples of the fungus for analysis at the CDFA Plant Pathology Laboratory, and for official record.  Ganoderma adspersum has not been reported earlier from California or North America (Rizzo, 2017a).  The potential risk of infestation of G. adspersum is assessed here and a permanent rating is proposed for the species.

History & Status:

Background:   Ganoderma adspersum is a wood-decaying fungus that occurs in a very wide range of tree species including deciduous trees and conifers throughout the world. The species has more frequently been detected in trees growing near human habitations, gardens, parks, and planted sites (Papp & Szabo, 2013; De Simone & Annesi, 2012).   Ganoderma adspersum is a pathogen of roots and butts of living trees causing white rot, and can continue to grow saprophytically on nonliving tissue such as, stumps of felled trees (De Simone & Annesi, 2012).  Ganoderma species often kill their hosts and frequently, a diseased tree breaks or is wind-thrown while still alive as a result of decay in the butt and base of the trunk (Sinclair & Lyon, 2005). Unlike other closely related species, G. adspersum is an aggressive species that is able to penetrate and break through intact reaction zones of infected wood causing progressive and extensive decay over a relatively short period of time (De Simone & Annesi, 2012).   In Italy, G. adspersum-infected pine stands were felled within two years of infection (De Simone & Annesi, 2012).

Ganoderma adspersum has been known by several names.  The fungus was originally found growing on Carpinus betulus (European hornbeam) in Croatia, and published by Schulzer 1878 as Polyporus adspersus, and later as P. linhartii Kalchbr. 1884, Ganoderma linhartii (Kalchbr.) Z. Igmándy 1968, and G. europaeum Steyaert 1961.  After studying all specimens under the different species names, in 1969, Donk concluded the correct name for the fungus, G. adspersum (Tortic, 1971). In European polypore monographs, G. adspersum was found under the name, G. australe (Fr.) Pat. 1889.  However, through molecular analysis, the European taxon (G. adspersum) was differentiated from the Australian taxon (G. australe).  Ganoderma adspersum is the name of the European species (Papp & Szabó, 2013).  Differentiation of species of Ganoderma is confusing and problematic with only seven species, including G. adspersum, being accepted in the European polypore monographs (Papp & Szabó, 2013).  Taxonomically, G. adspersum is a distinct species belonging to the G. applanatum – australe complex (Papp & Szabó, 2013).

The species was first reported from Europe and is primarily found in that continent. However, it has also been found in Argentina, Brazil, American Samoa, and recently in the USA (California) (see: ‘Worldwide Distribution’).

In California, Ganoderma adspersum was detected in nine and ten year old almond orchards trees in Kings County during surveys of almonds for wood decay fungi in February 2016 (Rizzo, 2017a)  Over a three-year period, the orchard had experienced almost 20% tree loss, resulting in its removal by the end of 2016.  This detection marked a first for the fungus in California and North America.  Another detection was made in August 2016, in a twelve-year old almond orchard in Fresno County, and in 2017, additional infections were detected in Tulare, Kern, and Madera Counties (Rizzo, 2017b).  Presently, in California, the fungus has been found only in almond, prune and peach. All surveyed almond trees were planted on peach rootstock (Rizzo, 2017b).

Disease development:  Generally, most infections are initiated by airborne basidiospores that enter wounds on roots and trunk bases.  Basidiocarps (fruiting bodies or conks containing numerous spore producing structures or basidia) usually grow from the vicinity of old wounds.  Basidiospores are produced in great numbers during evening hours when the air is humid.  Experimentally, infection by root contact with previously colonized wood is also possible, although tree-to-tree spread has not been indicated by field observations (Sinclair & Lyon, 2005).

Dispersal and spread: Primarily by airborne basidiospores (De Simone & Annesi, 2012).

Hosts: Abies sp. (fir), A. alba (silver fir), Acer saccharinum (silver maple), Aesculus hippocastanum (horse chestnut), Betula pendula (European white birch), Broussonetia papyrifera (paper mulberry), Carpinus betulus (European hornbeam), Cedrus deodara (deodar cedar), Celtis occidentalis (common hackberry), Cercis siliquastrum (Judas tree), Fagus sylvatica (European/common beech), Fraximus sp. (ash), F. angustifolia subsp. danubialis (narrow-leafed ash), F. ornus (manna ash), Gleditschia triacanthos (honeylocust), Gymnocladus dioicus (Kentucky coffeetree), Juglans nigra (black walnut), Laurus nobilis (bay laurel), Picea abies (Norway spruce), Pinus sp. (pine), P. pinea (Italian stone pine), Platanus sp. (sycamore/plane trees), Populus alba (white poplar), P. nigra (black poplar), Prunus avium (wild cherry), P. padus (European bird cherry), P. cerasus (sour cherry), P. domestica (European plum), P. dulcis (almond), P. persica (peach), Prunus sp. (plum), Robinia sp. (locusts), R. pseudoacacia (black locust),  Quercus sp. (oak), Q. cerris (Turkey oak), Q. petraea (sessile oak), Q. pubescens (downy oak ), Q. robur (English oak), Q. ilex (holly oak), Morus sp. (mulberry), Salix sp. (willow), Tilia sp. (basswood), T. cordata (littleleaf linden), Ulmus laevis (European white elm), Zelkova serrata (Japanese zelkova) (De Simone & Annesi, 2012; Farr & Rossman, 2017; Gottlieb et al., 1998; Papp, 2013; Rizzo, 2017b; Tortic, 1970);

Symptoms:  In general, trees affected by Ganoderma develop widespread decay of sapwood in the butt and major roots.  Other symptoms include loss of vigor, undersized and sometimes yellowing or wilting leaves, thin crowns, and dead branches.  Some infected trees may die while others are weakened and fall by windstorms as a result of decay.  In advanced stages of decay, wood is light colored and stringy or spongy.  Large, reddish brown basidiocarps of G. adspersum grow from roots or butts (Sinclair & Lyon, 2005).  Progression of decay may be favored by predisposing conditions such as wounds, excessive stem density, or water stress (De Simone & Annesi, 2012).

Damage Potential:  Ganoderma adspersum causes wood decay and root rot thereby decreasing structural strength, growth and stand of infected trees.  In California, Rizzo (2017b) reported 50% to 70% infection rates in almond and prune orchards, with tree loss being exponential over time. Very high infection levels were observed in 9-12 years old almond orchards.  The life span of a typical almond orchard is about 25 years.  However, extensive infections may be terminal for almond orchards.  Few orchards were removed entirely due to high infections of Ganoderma adspersum.

Worldwide Distribution: Europe: Belgium, England, Germany, Hungary, Italy, Yugoslavia; North America: USA (California); South America: Argentina; Brazil; Oceania: American Samoa (CABI, 2017; De Simone & Annesi, 2012; Farr & Rossman, 2017; Gottlieb et al., 1998; Tortic, 1971)

Official Control: No official controls are reported for Ganoderma adspersum.  However, Ganoderma spp. is on the “Harmful Organism Lists” for Colombia and Jamaica.  Shipments of Ganoderma spp.-free Phoenix dactylifera, (date palm) plants is required by Colombia (USDA PCIT, 2017).

California Distribution: Ganoderma adspersum has been found in almond and prune orchards in Fresno, Kings, Tulare, Kern, and Madera Counties (Rizzo, 2017b).

California Interceptions: None reported.

The risk Ganoderma adspersum would pose to California is evaluated below. 

Consequences of Introduction: 

1) Climate/Host Interaction: Presently, Ganoderma adspersum has been found in almond and prune orchards within the San Joaquin Valley.  It has therefore demonstrated its capability to establish under suitable climates for those hosts within the State.

Evaluate if the pest would have suitable hosts and climate to establish in California.

Score: 3

– Low (1) Not likely to establish in California; or likely to establish in very limited areas.

– Medium (2) may be able to establish in a larger but limited part of California.

– High (3) likely to establish a widespread distribution in California.

2) Known Pest Host Range: Ganoderma adspersum has a wide host range which includes deciduous and confer trees reported worldwide.  However, in California, the fungus has presently been detected in almond, prune and peach (almond on peach root stock) (Rizzo, 2017b). Those fruit hosts are cultivated in significant acreage in California.

Evaluate the host range of the pest.

Score: 3

– Low (1) has a very limited host range.

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

3) Pest Dispersal Potential: Numerous basidiospores are produced by the fungus but are dependent on wind currents for dispersal and spread to non-infected trees. Therefore, a Medium rating is given for high reproductive potential.

Evaluate the natural and artificial dispersal potential of the pest.

Score: 2

– Low (1) does not have high reproductive or dispersal potential.

– Medium (2) has either high reproductive or dispersal potential.

– High (3) has both high reproduction and dispersal potential.

4) Economic Impact: Rizzo (2017b) reported 50% to 70% infection rates in almond and prune orchards in California, with tree loss being exponential over time.  Ganoderma adspersum causes wood decay and root rot resulting in decreased structural strength, growth and stand of infected trees.  Few orchards were removed entirely due to high infections.

Evaluate the economic impact of the pest to California using the criteria below.

Economic Impact: A, B, C

A. The pest could lower crop yield.

B. The pest could lower crop value (includes increasing crop production costs).

C. The pest could trigger the loss of markets (includes quarantines).

D. The pest could negatively change normal cultural practices.

E. The pest can vector, or is vectored, by another pestiferous organism.

F. The organism is injurious or poisonous to agriculturally important animals.

G. The organism can interfere with the delivery or supply of water for agricultural uses.

Economic Impact Score: 3

– Low (1) causes 0 or 1 of these impacts.

– Medium (2) causes 2 of these impacts.

– High (3) causes 3 or more of these impacts.

5) Environmental Impact: Ganoderma adspersum has been reported on several hosts that are found in California environments.  Internationally, the fungus has more frequently been detected in trees growing near human habitations, gardens, parks, and planted sites.  However, in California, the fungus has only been detected in cultivated almond and prune. Other hosts may be threatened if the almond isolate in California is able to infect them.  However, as presently this is not known, the fungus is given a Medium score for potentially impacting urban gardens and plantings.

Evaluate the environmental impact of the pest on California using the criteria below.

Environmental Impact: E

A. The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.

B. The pest could directly affect threatened or endangered species.

C. The pest could impact threatened or endangered species by disrupting critical habitats.

D. The pest could trigger additional official or private treatment programs.

E. The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.

Environmental Impact Score: 2

– Low (1) causes none of the above to occur.

– Medium (2) causes one of the above to occur.

– High (3) causes two or more of the above to occur.

Consequences of Introduction to California for Ganoderma adspersum: High (13).

Add up the total score and include it here.

-Low = 5-8 points

-Medium = 9-12 points

–High = 13-15 points

6) Post Entry Distribution and Survey Information: Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included.

Evaluation is Medium (-2).  Ganoderma adspersum has been reported (Rizzo, 2017a, 2017b) from Fresno, Kings, Tulare, Kern, and Madera Counties.

Score: (-2)

-Not established (0) Pest never detected in California, or known only from incursions.

-Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).

–Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.

-High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

Final Score:

7) The final score is the consequences of introduction score minus the post entry distribution and survey information score: (Score)

Final Score:  Score of Consequences of Introduction – Score of Post Entry Distribution and Survey Information = 11.

Uncertainty:  

Presently, in California, Ganoderma adspersum has only been found in almond, prune, and almond on peach rootstock.  The fungus has a wide host range, but it is not known if other hosts, in particular those in natural environments of California, have been infected or will be infected by the almond isolate of the fungus.  Future information on its distribution may alter the numerical score but less likely, the proposed rating.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Ganoderma adspersum is B.

References:

Agrios, G. N.  2005.  Plant Pathology Fifth Edition.  Elsevier Academic Press.  922 p.

De Simone, D., and T. Annesi.  2012. Occurrence of Ganoderma adspersum on Pinus pinea.  Phytopathologia Mediterranea 51: 374-382.

CABI.  2017.   Ganoderma adspersum basic datasheet. http://www.cabi.org/cpc/datasheet/24922

Farr, D. F., and A. Y. Rossman.  2017.  Fungal Databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved March 8, 2017, from http://nt.ars-grin.gov/fungaldatabases/

Gottlieb A. M., B. O Saidman, and J. E. Wright, 1998. Isoenzymes of Ganoderma species from southern South America. Mycological Research 102, 415‒426.

Papp, V. and I. Szabó.  2013.  Distribution and host preferences of poroid Basidiomycete in Hungary I. – Ganoderma.  Acta Silv. Lingn. Hung. 9: 71-83.  DOI: 10.2478/aslh-2013-0006

Rizzo, D.  2017a. Email from David Rizzo, University of California, Davis, to Cheryl Blomquist, CDFA, sent Wednesday, January 25, 2017 6:09 am, forwarded to John Chitambar, CDFA, Wednesday, January 25, 2017 8:03:08 am.

Rizzo, D.  2017b. Email from David Rizzo, University of California, Davis to John Chitambar, CDFA, Tuesday, March 7, 2017 12:33 pm.

Sinclair, W. A., and H. H. Lyon.  2005.  Diseases of trees and shrubs second edition.  Comstock Publishing Associates, a division of Cornell University Press, Ithaca and London.  660 p.

Tortic, M.  1971.  Ganoderma adspersum (s. Schulz.) Donk (Ganoderma europaeum Steyaert) and its distribution in Yugoslavia.  Acta Botanica Croatica. 30: 113-118.

USDA PCIT.  2017.  USDA Phytosanitary Certificate Issuance & Tracking System.  https://pcit.aphis.usda.gov/PExD/faces/ReportHarmOrgs.jsp.

Responsible Party:

John J. Chitambar, Primary Plant Pathologist/Nematologist, California Department of Food and Agriculture, 3294 Meadowview Road, Sacramento, CA 95832. Phone: 916-262-1110, plant.health[@]cdfa.ca.gov.

Comment Format:

♦  Comments should refer to the appropriate California Pest Rating Proposal Form subsection(s) being commented on, as shown below.

Example Comment:
Consequences of Introduction:  1. Climate/Host Interaction: [Your comment that relates to “Climate/Host Interaction” here.]

♦  Posted comments will not be able to be viewed immediately.

♦  Comments may not be posted if they:

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♦  Comments may be edited prior to posting to ensure they are entirely germane.

♦  Posted comments shall be those which have been approved in content and posted to the website to be viewed, not just submitted.

Pest Rating: B

Posted by ls

Fungi, Plant Pathogens

Diaporthe pseudomangiferae

 California Pest Rating for
Diaporthe pseudomangiferae R. R. Gomes, C. Glienke & Crous
Pest Rating: C
PEST RATING PROFILE
Initiating Event:

On December 15, 2016, a shipment of Cacao seed pods with symptoms of necrotic spotting and rot and destined to a private citizen in Contra Costa County, was intercepted by the CDFA Dog Team at the United States Postal Service in Oakland, Alameda County.  The shipment was confiscated and destroyed and a sample of symptomatic seed pods was sent to the CDFA Plant Diagnostics Branch for disease diagnosis.  Suzanne Latham, CDFA plant pathologist identified the fungal pathogen, Diaporthe pseudomangiferae, as the cause for the disease and marked the first detection of D. pseudomangiferae in California.  The current status and rating of D. pseudomangiferae in California is assessed and a permanent rating is proposed.

History & Status:

Background:  Diaporthe pseudomangiferae is a fungal plant pathogen belonging to the order Diaporthales.  The species was named after its morphological similarity to the Phomopsis mangiferae, which was originally isolated from dead leaves of Mangifera indica in Pakistan, however, later reported to differ morphologically from P. mangiferae (Gomes et al., 2013).  Presently, D. pseudomangiferae has only been reported from the Dominican Republic, Puerto Rico, and Mexico (Farr & Rossman, 2017).

Diaporthe pseudomangiferae is not reported from the USA.  The pathogen is not established in California but was detected in a mail shipment of Cacao seed pods which was intercepted in California and subsequently, confiscated, bagged, frozen, and disposed.  However, its detection in Cacao marks a new host for the pathogen, which until now, has only been reported from mango (Gomes et al., 2013).

Disease development:  While specific information is lacking, it is likely that plant infection and disease development caused by Diaporthe pseudomangiferae are similar to those caused by other species of Diaporthe occurring as plant pathogens, endophytes or saprobes.  The fungus produces ascospores (sexual spores) in perithecia (sexual fruiting bodies) and conidia (asexual spores) in pycnidia on dead twigs and leaves.  Conidia are the main inoculum causing primary and secondary infections and are spread to host plants by splashing rains.  Ascospores may be involved in long distance dispersal of the pathogen.  The fungus is likely to overwinter as mycelium and/or as conidia within pycnidia (Agrios, 2005).

Dispersal and spread: Windblown/splashing rain and irrigation water, pruning tools, possibly insects, and animals can spread fungal spores to non-infected plants.

Hosts: Mangifera indica (mango) (Farr & Rossman, 2017; Gomes et al., 2013; Serrato-Diaz et al., 2014); Cacao sp. (CDFA Pest and Damage Record, 2016).

Symptoms:  In mango, Diaporthe pseudomangiferae causes inflorescence rot, rachis canker, and flower abortion.  Symptoms are characterized by blackening of plant tissue with soft rot lesions and sunken lesions on the rachis respectively.  In pathogenicity tests, initially white mycelia developed on inflorescences which later turned brown and flowers aborted (Serrato-Diaz et al., 2014).

Damage Potential:  Quantitative losses caused by Diaporthe pseudomangiferae have not been reported.  During a two-year disease survey in Puerto Rico, Serrato-Diaz et al., (2014) found 50% of mango symptomatic inflorescences to be infected with D. pseudomangiferae. The pathogen causes inflorescence rot, rachis canker, and flower abortion of mango. Therefore, if left uncontrolled, infections may result in reduced fruit production and marketability.  In California, nurseries and other growers of mango plants may be at risk of damage caused by this pathogen.

Worldwide Distribution: Caribbean: Dominican Republic, Puerto Rico; North America: Mexico (Farr & Rossman, 2016; Gomes et al., 2013; Serrato-Diaz et al., 2014).

Official Control: None reported.  In California, currently Diaporthe pseudomangiferae is a quarantine actionable pathogen with a temporary Q rating.

California Distribution: Diaporthe pseudomangiferae is not known to be established in California.

California Interceptions: There has been only one interception.  On December 15, 2016, the fungal pathogen was detected in a shipment of Cacao seed pods that originated in Puerto Rico and was intercepted at a United States Postal Service in Alameda County (see: ‘Initiating Event’).

The risk Diaporthe pseudomangiferae would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: Mango is the only known host in California.  Diaporthe pseudomangiferae may be able to infect its host under wet conditions and is therefore, only likely to establish in very limited regions of the State where mango is grown mainly in the Coachella valley and foothill regions of southern California.

Evaluate if the pest would have suitable hosts and climate to establish in California.

Score: 1

– Low (1) Not likely to establish in California; or likely to establish in very limited areas.

– Medium (2) may be able to establish in a larger but limited part of California.

– High (3) likely to establish a widespread distribution in California.

2) Known Pest Host Range: The host range of the pathogen is presently limited to Mangifera indica and Cacao

Evaluate the host range of the pest.

Score: 1

– Low (1) has a very limited host range.

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

3) Pest Dispersal Potential: Diaporthe pseudomangiferae has high reproductive potential with an abundant production of spores, however, the spores are dependent on splashing water for dispersal.

Evaluate the natural and artificial dispersal potential of the pest.

Score: 2

– Low (1) does not have high reproductive or dispersal potential.

– Medium (2) has either high reproductive or dispersal potential.

– High (3) has both high reproduction and dispersal potential.

4) Economic Impact: Under favorable wet conditions for spread and disease development, Diaporthe pseudomangiferae has been found to cause inflorescence rot, rachis canker, and aborted flowers in mango, thereby possibly resulting in lowered fruit production, value, and loss of markets.

Evaluate the economic impact of the pest to California using the criteria below.

Economic Impact: A, B, C

A. The pest could lower crop yield.

B. The pest could lower crop value (includes increasing crop production costs).

C. The pest could trigger the loss of markets (includes quarantines).

D. The pest could negatively change normal cultural practices.

E. The pest can vector, or is vectored, by another pestiferous organism.

F. The organism is injurious or poisonous to agriculturally important animals.

G. The organism can interfere with the delivery or supply of water for agricultural uses.

Economic Impact Score: 3

– Low (1) causes 0 or 1 of these impacts.

– Medium (2) causes 2 of these impacts.

– High (3) causes 3 or more of these impacts.

5) Environmental Impact: Mango and cacao are the only known hosts, therefore no significant impact on the environment is expected.

Evaluate the environmental impact of the pest on California using the criteria below.

Environmental Impact:  None

A. The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.

B. The pest could directly affect threatened or endangered species.

C. The pest could impact threatened or endangered species by disrupting critical habitats.

D. The pest could trigger additional official or private treatment programs.

E. The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.

Environmental Impact Score: 1

– Low (1) causes none of the above to occur.

– Medium (2) causes one of the above to occur.

– High (3) causes two or more of the above to occur.

Consequences of Introduction to California for Diaporthe pseudomangiferae: Low (8)

Add up the total score and include it here.

–Low = 5-8 points

-Medium = 9-12 points

-High = 13-15 points

6) Post Entry Distribution and Survey Information: Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included.

Evaluation is ‘Not established’ (0).

Score: (0)

–Not established (0) Pest never detected in California, or known only from incursions.

-Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).

-Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.

-High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

Final Score:

7) The final score is the consequences of introduction score minus the post entry distribution and survey information score: (Score)

Final Score:  Score of Consequences of Introduction – Score of Post Entry Distribution and Survey Information = 8.

Uncertainty: 

None.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Diaporthe pseudomangiferae is C.

References:

Agrios, G. N.  2005.  Plant Pathology Fifth Edition.  Elsevier Academic Press.  922 p.

Anon.  1996. Mango Mangifera indica L. California Rare Fruit Growers, Inc.  http://www.crfg.org/pubs/ff/mango.html

Farr, D. F., and A. Y. Rossman.  2017.  Fungal Databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved January 18, 2017, from http://nt.ars-grin.gov/fungaldatabases/

Gomes, R.R., C. Glienke, S. I. R. Videira, L. Lombard, J. Z. Groenewald, and P. W. Crous.  2013.  Diaporthe: a genus of endophytic, saprobic and plant pathogenic fungi. Persoonia 31: 1-41.

Serrato-Diaz, L.M., L. I. Rivera-Vargas, and R. D. French-Monar.  2014.  First report of Diaporthe pseudomangiferae causing inflorescence rot, rachis canker, and flower abortion of mango. Plant Disease 98(7): 1004

Responsible Party:

John J. Chitambar, Primary Plant Pathologist/Nematologist, California Department of Food and Agriculture, 3294 Meadowview Road, Sacramento, CA 95832. Phone: 916-262-1110, plant.health[@]cdfa.ca.gov.

Comment Format:

♦  Comments should refer to the appropriate California Pest Rating Proposal Form subsection(s) being commented on, as shown below.

Example Comment:
Consequences of Introduction:  1. Climate/Host Interaction: [Your comment that relates to “Climate/Host Interaction” here.]

♦  Posted comments will not be able to be viewed immediately.

♦  Comments may not be posted if they:

Contain inappropriate language which is not germane to the pest rating proposal;

Contains defamatory, false, inaccurate, abusive, obscene, pornographic, sexually oriented, threatening, racially offensive, discriminatory or illegal material;

Violates agency regulations prohibiting sexual harassment or other forms of discrimination;

Violates agency regulations prohibiting workplace violence, including threats.

Pest Rating: C

Posted by ls