Tag Archives: plant pathogens

Fungi, Plant Pathogens

Colletotrichum fructicola Prihastuti, L. Cai & K. D. Hyde, 2009

California Pest Rating for
Colletotrichum fructicola Prihastuti, L. Cai & K. D. Hyde, 2009
Pest Rating:  B
PEST RATING PROFILE
Initiating Event:

On March 29, 2016, a shipment of Chinese evergreen (Aglaonema sp.)  cuttings showing leaf spotting symptoms and destined to a nursery in San Luis Obispo County, was intercepted and sampled by San Luis Obispo County Agricultural officials.  The shipment had originated in Costa Rica.  Diseased plant samples were sent to the CDFA Plant Diagnostics Branch for diagnosis.  Suzanne Latham, CDFA plant pathologist, identified the anthracnose and fruit rot pathogen, Colletotrichum fructicola, as the cause for the disease.  This species was first detected within California on August 26, 2015, in mango fruit shipped from Puerto Rico and intercepted by the California Dog Team.  The fruit shipment was destined to a private citizen in Sacramento County.  The identity of the fungal pathogen was confirmed on August 18, 2015, by the USDA National Identification Services at Beltsville, Maryland.  Several detections of C. fructicola followed the initial find: on August 14, 2015, in Cymbidium orchid leaves from a nursery in San Diego County; on August 19, 2015, on mango fruit from Florida and destined for Stanislaus County; on November 9, 2015, in Dracaena massangeana cuttings from Costa Rica and destined to a nursery in San Diego County; on March 15, 2016, in black sapote fruit from Florida and destined to a private citizen in Los Angeles County.  In all these cases, subsequent to the detection of C. fructicola, all fruit and plant shipments/nursery stock were either destroyed or rejected from entering California.  Currently, C. fructicola has a temporary ‘Q’ rating.  The risk of introduction and establishment of this pathogen in California is assessed and a permanent rating is proposed herein.

History & Status:

Background:  Colletotrichum fructicola was originally reported to be associated with coffee berries (Coffea arabica) in northern Thailand (Prihastuti et al., 2009) and as a leaf endophyte from Central America (as C. ignotum). Since then, C. fructicola has been found on several tropical and subtropical hosts from diverse geographical regions. In the USA, C. fructicola was reported in 2012 from Florida and North Carolina on strawberry crown and apple fruit respectively (Weir et al., 2012). During 2015-16, the pathogen was also detected in California associated with several quarantine nursery plant/fruit shipments and regulatory nursery samples.

The pathogen is a distinct fungus species belonging to the vastly morphological and physiological variable C. gloeosporioides complex and is generally identified from other species of the complex only by gene sequencing.  However, C. ignotum and Glomerella cingulata var. minor are synonyms of C. fructicola (Prihastuti et al., 2009; Rojas et al., 2010; Weir et al, 2012).

Hosts: Aglaonema sp. (Chinese evergreen), Annona reticulata (custard apple), A. squamosa (sugar apples), Artocarpus heterophyllus (jackfruit), Coffea arabica (coffee), Coffea sp., Camellia japonica (Japanese camellia), Camellia sinensis (tea), Camellia sp., Capsicum frutescens (chili pepper), Carica papaya (papaya), Cestrum parqui (green cestrum), Citrullus vulgaris (watermelon), Citrus limon (lemon), C. reticulata (Mandarin orange), C. sinensis (sweet orange), Citrus x paradisi, Crinum asiaticum (spider lily), Cucumis sativus (cucumber), Cymbidium sp. (orchid), Dendrobium sp. (orchid), Dioscorea alata (purple yam), D. rotundata (white yam), Diospyros nigra (black sapote), Dracaena massangeana (corn plant/cornstalk Dracaena), Epidendrum sp. (orchid), Ficus carica (common fig), F. edulis (fig), F. pumila (creeping fig), Fortunella margarita (oval kumquat) Fragaria ananassa (strawberry), Limonium sinuatum (statice), Limonium sp., Lobularia maritima (sweet alyssum), Lupinus angustifolius (blue lupine), Lycopersicon esculentum (tomato), Lycium chinensis (boxthorn), Malus domestica (apple), M. sylvestris (crab apple), Mangifera indica (mango), Matthiola incana (stock), Medicago polymorpha (burclover), Musa acuminata (edible banana), Nerium oleander (oleander), Nicotiana tabacum (tobacco), Passiflora edulis (passion fruit), Persea americana (avocado), Phalaenopsis sp. (moth orchid), Phormium tenax (flax), Portulaca oleracea (little hogweed/common purslane), Psidium guajava (guava), Pyrus bretschneideri (Chinese white pear), P. pyrifolia (pear), Saccolabium sp. (orchid), Tetragastris panamensis, Theobroma cacao (cocoa), Vanda sp. (orchid) (Farr & Rossman, 2016; Li et al., 2014; Prihastuti et al., 2009; Wang et al., 2016, Weir et al., 2012; Zhang et al., 2015).

Symptoms:  Generally, Colletotrichum-infected host plants exhibit symptoms of anthracnose which include dark brown leaf, stem and fruit spots, fruit rot, and wilting of leaves which often result in dieback and reduction in plant quality.  In China, early stages of the disease in pear was characterized by the presence of black spots on young fruit which was always followed by severe bitter rot in matured fruit, and less than 1 mm black spots on leaves resulting in severe defoliation and loss of fruit (Jiang et al., 2014; Zhang et al., 2015). Anthracnose symptoms on tobacco leaves initiate as discrete, yellow-green spots which coalesce into larger lesions with white centers and dark brown margins (Wang et al., 2016).

Damage Potential:  Anthracnose disease caused by Colletotrichum fructicola can result in reduced plant quality and growth, fruit production and marketability.   In China, sudden outbreaks of the disease resulted in severe defoliation and a loss of pear fruit quality and yield resulting in fresh market losses ranging from 60-90% which, in 2008, were estimated at US$150 million. (Li, et al., 2013; Zhang, et al., 2015).  In 2014, also in China, 90% of tobacco leaves on ~2% plants in a 3-ha commercial tobacco field were infected with C. fructicola (Wang, et al., 2016).  In California, nursery production of potted host plants or in greenhouses are particularly at risk as nursery conditions are often conducive to infection by Colletotrichum species.  In California’s cultivated fields, disease development may be sporadic as it is affected by levels of pathogen inoculum and environmental conditions.

Disease Cycle:  It is likely that Colletotrichum fructicola has a similar life cycle to that of other Colletotrichum species and survives between crops during winter as mycelium on plant residue in soil, on infected plants, and on seeds.  During active growth, the pathogen produces masses of hyphae (stromata) which bear conidiophores, on the plant surface. Conidia (spores) are produced at the tips of the conidiophores and disseminated by wind, rain, cultivation tools, equipment, and field workers.   Conidia are transmitted to host plants.  Humid, wet, rainy weather is necessary for infection to occur.  These requirements in particular may limit the occurrence of the pathogen in California fields and subsequently, the pathogen may be more of a problem under controlled environments of greenhouses.  Conidia germinate, penetrate host tissue by means of specialized hyphae (appresoria) and invade host tissue.

Transmission:  Wind, wind-driven rain, cultivation tools, and human contact.

Worldwide Distribution: Asia: China, India, Israel, Japan, Korea, Thailand; Africa: Angola, Nigeria; Europe: United Kingdom; North America: Canada, Panama, USA (California, Florida, North Carolina); Australia (Farr & Rossman, 2016; Li et al., 2014; Prihastuti et al., 2009; Wang et al., 2016, Weir et al., 2012; Zhang et al., 2015).

Official Control:  In California C. fructicola is an actionable, Q-rated pathogen, and infected plant material is subject to destruction or rejection.

California Distribution: Colletotrichum fructicola was detected in a nursery in San Diego County (see “Initiating Event”).

California Interceptions:  During 2015-16, Colletotrichum fructicola has been intercepted several times mainly in shipments of mango and black sapote fruits, Dracaena and Chinese evergreen cuttings that originated in Costa Rica, Puerto Rico, and Florida (see ‘Initiating event’).

The risk Colletotrichum fructicola would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: Evaluate if the pest would have suitable hosts and climate to establish in California. Score:

– 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.

Risk is Medium (2) – Similar to other species of Colletotrichum, C. fructicola requires humid, wet, rainy weather for conidia to infect host plants. This environmental requirement may limit the ability of the pathogen to fully establish and spread under dry field conditions in California.

2) Known Pest Host Range: Evaluate the host range of the pest. Score:

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

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

Risk is High (3) – The host range of Colletotrichum fructicola is relatively wide and diverse and includes several tropical and subtropical plants, as well as agricultural and ornamental crops grown in California.

3) Pest Dispersal Potential: Evaluate the natural and artificial dispersal potential of the pest. Score:

– 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.

Risk is High (3) – The pathogen has high reproductive potential and conidia are produced successively.  They are transmitted by wind, wind-driven rain, cultivation tools, and human contact however conidial germination and plant infection require long, wet periods.

4) Economic Impact: Evaluate the economic impact of the pest to California using the criteria below. Score:

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.

– 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.

Risk is High (3) –Under suitable, wet climates, the pathogen could lower plant growth, fruit production and value and trigger the loss of markets.

5) Environmental Impact: Evaluate the environmental impact of the pest on California using the criteria below.

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

The pest could directly affect threatened or endangered species.

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

The pest could trigger additional official or private treatment programs.

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

Score the pest for Environmental Impact. Score:

– 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.

Risk is Medium (2) – The pathogen could significantly impact cultural practices or home garden plantings.

Consequences of Introduction to California for Colletotrichum fructicola:

Add up the total score and include it here. (Score)

-Low = 5-8 points

-Medium = 9-12 points

–High = 13-15 points

Total points obtained on evaluation of consequences of introduction of Colletotrichum fructicola to California = (13).

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. (Score)

-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.

Evaluation is Low (-1) – Colletotrichum fructicola was detected in a nursery in San Diego County.

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 = 12.

Uncertainty:

Periodic surveys need to be conducted to confirm the presence/absence of C. fructicola in commercial and private production regions within California.  Subsequent results may alter the herein proposed rating for the pathogen.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for the anthracnose pathogen, Colletotrichum fructicola is B.

References:

CABI.  2016.  Colletotrichum fructicola basic datasheet report.  Crop Protection Compendium.  www.cabi.org/cpc/

Farr, D. F., & A. Y. Rossman.  Fungal databases, systematic mycology and microbiology laboratory, ARS, USDA. Retrieved April 3, 2016, from

http://nt.ars-grin.gov/fungaldatabases/

J. Jiang, Zhai, H. Li, Z. Wang, Y. Chen, N. Hong, G. Wang, G. N. Chofong, and W. Xu. 2014. Identification and characterization of Colletotrichum fructicola causing black spots on young fruits related to bitter rot of pear (Pyrus bretschneideri Rehd.) in China.  Crop Protection 58:41-48.

Li, H.N., Jiang, J.J., Hong, N., Wang, G.-P., and Xu, W.X. 2013. First Report of Colletotrichum fructicola Causing Bitter Rot of Pear (Pyrus bretschneideri) in China. Plant Disease 97:1000. http://dx.doi.org/10.1094/PDIS-01-13-0084-PDN.

Prihastuti, H., L. Cai, H. Chen, E. H. C. McKenzie, and K. D. Hyde.  2009. Characterization of Colletotrichum species associated with coffee berries in northern Thailand. Fungal Diversity 39: 89-109.

Wang, H. C., Y. F. Huang, Q. Chen, M. S. Wang, H. Q. Xia, S. H. Shang, and C. Q. Zhang.  2016.  Anthracnose caused by Colletotrichum fructicola on tobacco (Nicotiana tabacum) in China.  Plant Disease (posted on line March 8, 2016). http://dx.doi.org/10.1094/PDIS-06-15-0724-PDN.

Weir, B. S., P. R. Johnston, and U. Damm.  2012.  The Colletotrichum gloeosporioides species complex.  Studies in Mycology, 73:115-180. DOI:10.3114/sim0011.

P. F. Zhang, L. F. Zhai, X. K. Zhang, X. Z. Huang, N. Hong, W. Xu, and G. Wang. Characterization of Colletotrichum fructicola, a new causal agent of leaf black spot disease of sandy pear (Pyrus pyrifolia).  European Journal of Plant Pathology 143:651-662.

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

Ascochyta aquilegiae (Rabenh.) Boerema, Fruyter & Noorder, 1997

California Pest Rating for
Ascochyta fungi (photo source: forestryimages.org)
Ascochyta fungi; Ascochyta spp. Lib.
Ascochyta aquilegiae (Rabenh.) Boerema, Fruyter & Noorder, 1997
Pest Rating:  C
PEST RATING PROFILE
Initiating Event:

On March 28, 2016, a sample of diseased Aquilegia sp. (columbine) plants showing symptoms of dieback, was voluntarily submitted by a nursery in Contra Costa County to the CDFA Plant Pathology Laboratory for disease diagnosis.  Suzanne Latham, CDFA plant pathologist, identified the associated fungus plant pathogen, Ascochyta aquilegiae, as the cause for the disease.  The pathogen was assigned a temporary “Z” rating as it has been reported earlier in California and is considered widely distributed.  That rating is reassessed here and a permanent rating is proposed.

History & Status:

Background:  Ascochyta aquilegiae causes dark leaf spots, stem lesions, and crown rots in plants belonging to the family Ranunculaceae, including several species in the genera Aquilegia and Delphinium.  The fungal species has undergone several name changes in fungal taxonomy and is known by several synonyms including, Stagonosporopsis aquilegiae, Actinonema aquilegiae, Ascochyta laskarisii, Diplodina delphinii, Phoma aquilegiicola, Phyllosticta aquilegiae, and Phyllosticta aquilegicola (Farr & Rossman, 2016).

Disease development and spread:  Ascochyta aquilegiae attack primarily plant leaves by means of spores (conidia) and, following infection, produce numerous condia that are spread to other plants by wind, wind-blown rain, water, and insects.  Conditions that favor prolonged leaf-wetness in warm climates often favor development of the pathogen. The pathogen is also transmitted to non-infected sites through the movement of infected plant materials and debris. The fungus overwinters primarily in fallen leaves or infected leaf debris, or as mycelium in infected tissues of perennial plants (Agrios, 2005; Pscheidt & Ocamb, 2016a, 2016b).

Hosts: Aquilegia spp. (columbine), Aconitum spp. (aconite/wolf’s bane), Clematis sp. (clematis), Consolida spp. (larkspur), Coptis chinensis (goldthread), Delphinium spp. (delphinium/larkspur) (Farr & Rossman, 2016; French, 1989; Garibaldi et al., 2011; Yu et al., 2014).

Symptoms and damage potential: Ascochyta aquilegiae causes leaf spots, stem cankers and crown rots.  Leaf lesions of infected Aquilegia and Coptis plants are extensive, usually beginning at the leaf margin and extending to the central leaf blade eventually coalescing to cover entire leaf, irregular, brown to black, necrotic, slightly sunken with a well-defined border and surrounded by a violet-brown halo.   As the disease progresses, stems are also affected causing death of the apical part of the plant (Garibaldi et al., 2011; Yu et al., 2014). In Delphinium spp., petioles develop brown water-soaked lesions near the base of succulent plants.  Less vigorous plants show black local lesions on the petiole.  Inflorescences and seed pods develop a blackish decay.  Generally, crown rot may be found in plants two years or older (Pscheidt & Ocamb, 2016a, 2016b).  Small, dark brown to black fungal fruiting bodies (pycnidia) may be present in the lesions.

Damage Potential:  While information on the economic importance of the disease caused by Ascochyta aquilegiae is limited, the development of leaf spots, stem cankers and crown rots in infected plants may result in reduced plant production, yield, and marketability of columbine and other host plants used in residential gardens and commercial landscapes.  Plants are particularly at risk of pathogen infection in warm and moist natural climates of California, and in nursery-controlled productions.  In China, A. aquilegiae caused yield losses of 15-75% in gold thread, an important herbaceous plant used in traditional Chinese medicine (Yu et al., 2014).

Worldwide Distribution:  Asia:  Armenia, China, Japan, Russia; Africa: South Africa, Zimbabwe, Europe: Bulgaria, Czechoslovakia, Germany, Italy, Netherlands, Poland, Scotland, United Kingdom; North America: Canada, USA; Oceania: New Zealand.  It is widespread within the USA in Alaska, California, Connecticut, Iowa, Idaho, Maryland, New Jersey, New York, Oregon, Pennsylvania, Texas, Washington, Wisconsin (Farr & Rossman, 2016; Garibaldi et al., 2011; Pscheidt & Ocamb, 2016a, 2016b; Yu et al., 2014).

Official Control: None reported. Currently, the pathogen has a temporary ‘Z’ rating in California, which indicates that it is a previously unrated organism of known economic and/or environmental detriment but generally distributed in the state.

California Distribution: Ascochyta aquilegiae has been detected in California’s northern and southern coastal counties which include: Del Norte, Humboldt, Mendocino, Sonoma, Marin, San Francisco, San Mateo, Santa Cruz, Alameda, Santa Clara, San Benito, Monterey, San Luis Obispo, Santa Barbara, Ventura, Los Angeles, Orange, and San Diego Counties (French, 1989).

California Interceptions: None reported.

The risk Ascochyta aquilegiae would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: Evaluate if the pest would have suitable hosts and climate to establish in California. Score:

– 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.

Risk is Medium (2): Conditions that favor prolonged leaf-wetness in warm climates often favor development of Ascochyta aquilegiae.  The pathogen is already known to be present in northern and southern coastal counties in California.

2) Known Pest Host Range: Evaluate the host range of the pest. Score:

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

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

Risk is Low (1): Presently, the host range is limited to few species within Ranunculaceae. 

3) Pest Dispersal Potential: Evaluate the natural and artificial dispersal potential of the pest. Score:

– 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.

Risk is Medium (2): Ascochyta aquilegiae produces numerous condia the infect plants, however, to spread to other plants, they are dependent on wind, wind-blown rain, water, and insects.  Furthermore, prolonged leaf-wetness in warm climates is needed to favor development of the pathogen in plants. The pathogen is also transmitted to non-infected sites through the movement of infected plant materials and debris.

4) Economic Impact: Evaluate the economic impact of the pest to California using the criteria below. Score:

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.

– 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.

Risk is Medium (2): While information on the economic importance of the disease caused by Ascochyta aquilegiae is limited, the development of leaf spots, stem cankers and crown rots in infected plants may result in reduced plant production value and marketability of columbine and other host plants used in residential gardens and commercial landscapes.  Plants are particularly at risk of pathogen infection in warm and moist natural climates of California, and in nursery-controlled productions

5) Environmental Impact: Evaluate the environmental impact of the pest on California using the criteria below.

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.

Score the pest for Environmental Impact. Score:

– 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.

Risk is High (3): Commercial landscape and home garden plantings could be negatively impacted if infected by Ascochyta aquilegiae under favorable moist climate conditions.  The pathogen could directly affect certain species of larkspur, namely, Delphinium bakeri (Baker’s larkspur), D. hesperium ssp. cuyamacae (Cuyanaca larkspur), D. luteum (golden larkspur), and D. variegatum ssp. kinkiense (San Clemente Island larkspur) included in the ‘State and Federally Listed Endangered, Threatened, and Rare Plants of California, July 2015’ thereby, potentially lowering biodiversity, natural communities or ecosystem processes.

Consequences of Introduction to California for Ascochyta aquilegiae:

Add up the total score and include it here. (Score)

-Low = 5-8 points

–Medium = 9-12 points

-High = 13-15 points

Total points obtained on evaluation of consequences of introduction to California = 10

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. (Score)

-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.

Evaluation is Medium (-2): Presently, Ascochyta aquilegiae is known to be present in northern and southern coastal counties in California.

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:   

The impact and spread of this pathogen to other intrastate regions where host species are grown, is not known.  Future reports of the detection of P. digitalidis in California could lower the overall score for the pathogen although it is unlikely to affect its final rating.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Ascochyta aquilegiae is C.

References:

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

Farr, D.F., & Rossman, A.Y. Fungal Databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved April 18, 2016, from http://nt.ars-grin.gov/fungaldatabases/.

Garibaldi, A., D. Bertetti, M. T. Amatulli, and M. L. Gullino.  2011.  First report of leaf spot of fan columbine (Aquilegia flabellata) caused by Phoma aquilegiicola in Italy.  Plant Disease 95:880.  http://dx.doi.org/10.1094/PDIS-05-10-0391.

Pscheidt, J.W., and Ocamb, C.M.  2016a. Columbine (Aquilegia spp.) leaf spots.  Pacific Northwest Plant Disease Management Handbook. © Oregon State University. pnwhandbooks.org/plantdisease/node/3020. http://pnwhandbooks.org/plantdisease/columbine-aquile.

Pscheidt, J.W., and Ocamb, C.M.  2016b. Delphinium – leaf spot and crown rot.  Pacific Northwest Plant Disease Management Handbook. © Oregon State University. pnwhandbooks.org/plantdisease/node/3118.  http://pnwhandbooks.org/plantdisease/delphinium-leaf-spot-and-crown-rot.

Yu, Y., Z. C. Su, W. Z. Tan, and C. W. Bi.  2014.  First report of a leaf spot on goldthread (Coptis chinensis) caused by Phoma aquilegiicola in China. Plant Disease 98:1428. http://dx.doi.org/10.1094/PDIS-01-14-0010-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.

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

Peronospora digitalidis Gäum, 1923

California Pest Rating for
Foxglove, Downy Mildew Plant Symptoms
Downy mildew does occur in the landscape in Washington. Note lesions with angular margins. ~ Photo Credit: Jenny Glass, 2011.
Peronospora digitalidis Gäum, 1923
Pest Rating: C
PEST RATING PROFILE
Initiating Event:

On February 9, 2016, USDA’s Animal and Plant Health Inspection Service (APHIS) notified the CDFA that the downy mildew pathogen, Peronospora digitalidis, was added on February 2, 2016, to their ‘List of Pests no Longer Regulated at U.S. Ports of Entry’ under the Federally Recognized State Managed Phytosanitary (FRSMP) program (USDA APHIS 2016).  Consequently, USDA APHIS will no longer take regulatory action this pathogen at ports of entry.  Therefore, and at the request of Stephen Brown, Assistant Director, CDFA, the risk of infestation and the current rating for P. digitalidis is re-assessed here.

History & Status:

Background:  Peronospora digitalidis is an oomycete in the order Peronosporales, which causes downy mildew disease of foxglove (Digitalis spp.).  The pathogen has been reported in Europe, Asia, and New Zealand, and was first reported from the United States, in 2002, on potted common foxglove plants in commercial nurseries in Santa Cruz County, California (Tjosvold & Koike, 2002).  It is likely that all affected nursery plants were destroyed, however, following its initial detection, in 2003, the pathogen continued to be found in several nurseries in California coastal counties and most recently in 2015 (CDFA Pest and Damage Records).

Disease cycle:  Peronospora digitalidis is an oomycete belonging to the family Peronosporaceae.  Generally, downy mildews overwinter as thick-walled resting spores called oospores that are produced through the fertilization of two mating types.  However, no oospores have so far been reported for this pathogen.  It is likely that the pathogen survives as mycelium and/or condia (spores) in infected plant buds, plant debris, leaf tissue and shoots.  Downy mildews are severe in cool or warm (but not hot), high humid climates and when a film of water is present on plant tissue.  They primarily cause foliar blights and rapidly spread in young green leaf, twig and fruit tissues.  Under favorable weather conditions, condia are carried by wind or water to wet leaves near the ground where they infect through stomata of the lower leaf surface.  A conidium germinates via a germ tube that grows through leaf stomata into intercellular spaces within the leaf tissue and eventually penetrates plant cells through special structures called haustoria.  Developing hypha that spreads intercellularly forms a cushion of mycelia just below the stomata.  From this cushion, conidophores arise and emerge through stomata.  At their tips, conidia (sporangia/spores) are produced simultaneously and are carried by wind and rain to new infection sites of the same or different plant.

Dispersal and spread:  The pathogen can spread through contaminated plant cuttings, transplants, fresh leaves and within seeds.  Also, it produces airborne conidia (spores) can disperse and be carried by moist winds.  It can also be present in soil associated with host and non-host plants and therefore, can spread by any means that aids in the movement of soil and/or water from infected plants to non-infected ones.

Hosts: Digitalis spp. (foxglove): D. purpurea, D. grandiflora, D. lutea, and Digitalis sp. (Farr & Rossman, 2016). Foxy hybrids are very susceptible and D. grandiflora was symptomless when grown in a heavily diseased region (Tjosvold & Koike, 2002).

Symptoms and damage potential: On leaves, initial symptoms consist of light green, rectangular areas that are delimited by veins.  Later, these spots become chlorotic, coalesce and turn necrotic and purplish-gray sporulation of the pathogen develops primarily on the underside of leaves and sometimes on upper surfaces of leaves (Pscheidt & Ocamb, 2016).

Damage Potential: While estimates of crop losses caused in particular by Peronospora digitalidis have not been reported, downy mildews can cause rapid and severe losses of young plants in seedbeds and in the field. Nursery stock producers and landscape growers of foxglove species may be at risk of damages caused by this downy mildew pathogen.

Worldwide Distribution: Europe: Czech Republic, Poland, Germany, Italy, United Kingdom, Scotland, Wales; North America: USA (California, Oregon, Washington) (Farr & Rossman, 2016; Garibaldi et al., 2013; Tjosvold & Koike, 2002; Pscheidt & Ocamb, 2016).

Official Control: Since 2002, Peronospora digitalidis has been on the North American Plant Protection Organization (NAPPO) “Alert List” (EPPO, 2016).  Since February 2, 2016, it has not been regulated by the USDA (see ‘Initiating event’). Currently, it has a “C” rating in California.

California Distribution: Orange, San Diego, San Luis Obispo, Santa Barbara, and Santa Cruz (CDFA Pest and Damage Records).

California Interceptions:  Peronospora digitalidis was detected in two nursery foxglove shipments imported to California in 2003.

The risk Downy mildew of foxglove would pose to California is evaluated below.

 Consequences of Introduction: 

 1) Climate/Host Interaction: Evaluate if the pest would have suitable hosts and climate to establish in California. Score:

– 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.

Risk is Medium (2):  Peronospora digitalidis is likely to establish in cool to warm and very humid to wet climates where foxglove grows in California.  According to the California Invasive Plant Council (2006-2016), foxglove is found along the coast northward from Santa Barbara, infesting moist meadows and roadsides and also in the northern Sierra Nevada foothills.

2) Known Pest Host Range: Evaluate the host range of the pest. Score:

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

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

Risk is Low (1): Presently, the host range is limited to few reported species of Digitalis. 

3) Pest Dispersal Potential: Evaluate the natural and artificial dispersal potential of the pest. Score:

– 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.

Risk is High (3): Conidia are easily produced simultaneously and in abundance.  The pathogen is transmitted via infected plant material; conidia are dispersed by winds, water and associated soil.   

4) Economic Impact: Evaluate the economic impact of the pest to California using the criteria below. Score:

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.

– 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.

Risk is High (3): While estimates of crop losses caused by Peronospora digitalidis have not been reported, presence of the pathogen in open fields/landscapes and/or in nursery stock produced in greenhouse environments are expected to cause severe damage under cool or warm and humid climates resulting in significantly lower crop value and yield.  Infected, symptomatic nursery stock plants are not marketable resulting in total loss in recovery of production costs.  Markets for crop sale are directly affected.  Normal cultivation practices, including delivery and supply of irrigation water, would need to be altered to prevent spread of the pathogen.

5) Environmental Impact: Evaluate the environmental impact of the pest on California using the criteria below.

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.

Score the pest for Environmental Impact. Score:

– 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.

Risk is Medium (2): Commercial landscape and home garden plantings of foxglove can be significantly impacted if infected by the downy mildew pathogen.  Under favorable climate conditions, disruption of natural communities and changes in ecosystem could occur with severe and widespread infestations of downy mildew. 

Consequences of Introduction to California for Downy mildew of foxglove:

Add up the total score and include it here. (Score)

-Low = 5-8 points

-Medium = 9-12 points

-High = 13-15 points

Total points obtained on evaluation of consequences of introduction to California = 11

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. (Score)

-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.

Evaluation is Medium (-2): Presently, the downy mildew pathogen, Peronospora digitalidis, has been reported from at least five coastal counties.

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:   

The impact and spread of this pathogen to other intrastate regions where Digitalis spp. is grown, is not known.  Future reports of the detection of P. digitalidis in California could lower the overall score for the pathogen although it is unlikely to affect its final rating.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Peronospora digitalidis is C.

References:

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

California Invasive Plant Council.  2006-2016. Invasive Plants of California’s Wildland Digitalis purpurea: http://www.cal-ipc.org/ip/management/ipcw/pages/detailreport.cfm@usernumber=42&surveynumber=182.php?print=y .

EPPO.  2016.  Peronospora digitalidis (PERODG).  New PQR database.  Paris, France: European and Mediterranean Plant Protection Organization.  http://newpqr.eppo.int.

Farr, D.F., & A. Y. Rossman.  Fungal Databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA.  Retrieved January 28, 2016, from http://nt.ars-grin.gov/fungaldatabases/.

Garibaldi, A., D. Bertetti, A. Poli, and M. L. Gullino.  2013.  Outbreak of downy mildew caused by Peronospora digitalidis on common foxglove (Digitalis purpurea) in Italy.  Journal of Plant Pathology 95:659-668. doi: 10.4454/JPP.V95I3.021.

Pscheidt, J. W., and C. M. Ocamb (Senior Eds.).  2016.  Foxglove (Digitalis spp.) downy mildew.  PNW Plant Disease Management Handbook: http://pnwhandbooks.org/plantdisease/foxglove-digitalis-spp-downy-mildew.

USDA APHIS.  2016.  FRSMP: Pests no longer regulation at U. S. ports of entry.  United States Department of Agriculture Animal and Plant Health Inspection Service.  https://www.aphis.usda.gov/aphis/ourfocus/planthealth/plant-pest-and-disease-programs/frsmp/ct_non-reg-pests.

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.]

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♦  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: C

Posted by ls

Fungi, Plant Pathogens

Colletotrichum siamense Prihastuti, L. Cai & K. D. Hyde, 2009

California Pest Rating Proposal for
Colletotrichum siamense Prihastuti, L. Cai & K. D. Hyde, 2009
Pest Rating: B
PEST RATING PROFILE
Initiating Event:  

On June 26, 2015, a California Dog Team intercepted Cacao seed pods with necrotic spots at a parcel distribution facility in Mariposa County and sent a sample to the CDFA Plant Diagnostics Branch for disease diagnosis.  The shipment had originated in Mircao, Puerto Rico and was destined to a private citizen in Mariposa County, California.  Suzanne Latham, CDFA plant pathologist identified the fungal anthracnose and fruit rot pathogen, Colletotrichum siamense as the cause for the disease and marked the first detection of C. siamense in California.  Several detections of this fungal pathogen followed the initial find: on October 8, 2015, in fruit of star fruit and Jew plum originating in Florida and destined for San Diego and Santa Clara Counties; on October 13, 2015, in avocado fruit from Puerto Rico and destined for Contra Costa County; on November 9, 2015, in fruit of two unknown hosts that originated from Florida.  In all these cases the fruit were intercepted by California Dog Teams and destined to private citizens in California. Consequent to these California detections, all infected plant materials were destroyed. The risk of infestation of C. siamense in California is evaluated and a permanent rating is proposed.

History & Status:

Background:  Colletotrichum siamense is a distinct fungus species belonging to the vastly morphological and physiological variable C. gloeosporioides and is genetically identified from other species of the complex.  However, C. jasmine-sambac and C. hymenocallidis are synonyms of C. siamense (Weir et al, 2012).  The species was originally described in 2009 from infected coffee berries (Coffea arabica) in Thailand.  Since then, it has been found on a wide range of hosts from several tropical and subtropical global regions.

Hosts:    Jackfruit (Artocarpus heterophyllus), bamboo orchid (Arundina graminifolia), neem (Azadirachta indica), capsicum (Capsicum annuum); papaya (Carica papaya), mandarin orange (Citrus reticulata), coffee (Coffea sp., C. arabica, C. canephora), dayflowers (Commelina sp.), Guinea yam (Dioscorea rotunda), loquat (Eriobotrya japonica), edible fig (Ficus carica), strawberry (Fragaria ananassa), spider lily (Hymenocallis sp., H. americana), jasmine (Jasminum sambac), apple (Malus domestica), mint (Mentha sp.), avocado (Persea Americana), black pepper (Piper nigrum), pistachio (Pistacia vera), king protea (Protea cynaroides), rosemary (Rosmarinus officinalis), cacao (Theobroma cacao), grape (Vitis vinifera) (Farr & Rossman, 2015).  Onion (Allium cepa) (Chowpadda et al., 2015), chili pepper (Capsicum sp.) (Sharma & Shenoy, 2014), bauhinia (Bauhinia forficate subsp. pruinosa) (Larran et al., 2015).  The recent California detections mentioned above include C. siamense in star fruit (Averrhoa carambola) and Jew plum (Spondias dulcis).

Symptoms:  Colletotrichum siamense causes leaf and fruit spots and leaf drop.  In mandarin orange, initial symptoms appeared on young leaves as reddish-brown lesions 2-5 mm in diameter. Several weeks later 20-70% of leaves had dropped and 10-50% exhibited brown spots 5-40 mm in diameter (Cheng, et al., 2013).  Circular or irregular light brown necrotic lesions surrounded by dark brown borders were present in bauhinia leaves in Argentina (Larran et al., 2015).  Generally, Colletotrichum-infected host plants exhibit symptoms of anthracnose which include dark brown leaf, stem and fruit spots and wilting of leaves which often result in dieback and reduction in plant quality.

Damage Potential:  Anthracnose disease caused by Colletotrichum siamense can result in reduced plant quality and growth, fruit production and marketability.  In China, about 15% yield losses was observed on different aged trees of mandarin orange, Citrus reticulata cv. Shiyue .  In California, nursery productions of fruit and ornamental plants are particularly at risk as nursery conditions are often conducive to infection by Colletotrichum species.  In open fields, disease development may be sporadic as it is affected by levels of pathogen inoculum and environmental conditions.

Disease Cycle:  It is likely that Colletotrichum siamense has a similar life cycle to that of other Colletotrichum species and survives between crops during winter as mycelium on plant residue in soil, on infected plants, and on seeds.  During active growth, the pathogen produces masses of hyphae (stromata) which bear conidiophores, on the plant surface. Conidia (spores) are produced at the tips of the conidiophores and disseminated by wind, rain, cultivation tools, equipment, and field workers.   Conidia are transmitted to host plants.  Humid, wet, rainy weather is necessary for infection to occur.  These requirements in particular may limit the occurrence of the pathogen in California fields and subsequently, the pathogen may be more of a problem under controlled environments of greenhouses.  Conidia germinate, penetrate host tissue by means of specialized hyphae (appresoria) and invade host tissue.

Transmission:  Wind, wind-driven rain, cultivation tools, and human contact.

Worldwide Distribution:  Colletotrichum siamense is distributed in Asia: China, India, Thailand, Vietnam; Africa: Kenya, Malawi, Nigeria, South Africa, Zimbabwe; North America: USA (Alabama, Florida, North Carolina); South America: Argentina, Brazil, Colombia; Australia (Farr & Rossman, 2015; Larran et al., 2015).

Official Control:  In California C. siamense is an actionable, Q-rated pathogen, and infected plant material is subject to destruction or rejection.

California Distribution: Colletotrichum siamense is not established in California (see “Initiating Event”).

California Interceptions: There have been seven interceptions of Colletotrichum siamense-infected fruit of avocado, star fruit, Jew plum, cacao seed pods, and two unknown hosts (see ‘Initiating event’).

The risk Colletotrichum siamense would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: Evaluate if the pest would have suitable hosts and climate to establish in California. Score:

– 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.

Risk is Medium (2) – Similar to other species of Colletotrichum siamense requires humid, wet, rainy weather for conidia to infect host plants. This environmental requirement and narrow host range may limit the ability of the pathogen to fully establish and spread under dry field conditions in mainly in southern California.

2) Known Pest Host Range: Evaluate the host range of the pest. Score:

– Low (1) has a very limited host range.
– Medium (2) has a moderate host range.
– High (3) has a wide host range.

Risk is High (3) – Colletotrichum siamense has a wide and diverse range of host plants grown in subtropical and tropical regions.  Several of these are grown in California and include grape, strawberry, apple, avocado, fig, and onion.     

3) Pest Dispersal Potential: Evaluate the natural and artificial dispersal potential of the pest. Score:

– 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.

Risk is High (3) – The pathogen has high reproductive potential and conidia are produced successively.  They are transmitted by wind, wind-driven rain, cultivation tools, and human contact however conidial germination and plant infection require long, wet periods.

4) Economic Impact: Evaluate the economic impact of the pest to California using the criteria below. Score:

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.

– 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.

Risk is Medium (2) –Anthracnose-infected fruit may result in lower crop value and market loss.  Its economic impact is evaluated as a medium risk.   

5)  Environmental Impact: Evaluate the environmental impact of the pest on California using the criteria below.

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.

Score the pest for Environmental Impact. Score:

– 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.

 Risk is Medium (2) – The pathogen could significantly impact backyard productions of fruit and ornamental plants wherever grown in California.

Consequences of Introduction to California for Colletotrichum siamense:

Add up the total score and include it here. (Score)

-Low = 5-8 points
–Medium = 9-12 points
-High = 13-15 points

Total points obtained on evaluation of consequences of introduction of Colletotrichum siamense to California = (12).

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. (Score)

–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.

Evaluation is not established (0).  Colletotrichum siamense is not established in California. 

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 = 12.

Uncertainty:

None.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for the anthracnose pathogen, Colletotrichum siamense is B.

References:

Cheng, B. P., Y. H. Huang, X. B. Song, A. T. Peng, J. F. Ling, and X. Chen.  2013.  First report of Colletotrichum siamense causing leaf drop and fruit spot of Citrus reticulata Blanco cv. Shiyue Ju in China.  Plant Disease 97:1508. http://dx.doi.org/10.1094/PDIS-04-13-0352-PDN.

Chowpadda, P., C. S. Chethana, and K. V. Pavani.  2015.  Colletotrichum siamense and C. truncatum are responsible for severe outbreaks of anthracnose on onion in southwest India.  Journal of Plant Pathology 97, No. 1: (abstract). doi: 10.4454/JPP.V97I1.015. Farr, D. F., & A. Y. Rossman.  Fungal databases, systematic mycology and microbiology laboratory, ARS, USDA. Retrieved April 7, 2015, from

http://nt.ars-grin.gov/fungaldatabases/

James, R.S., J.  Ray, Y. P. Tan and R. G. Shivas.  2014.  Colletotrichum siamense, C. theobromicola, and C. queenslandicum from several plant species and the identification of C. asianum in the Northern Territory, Australia. Australasian Plant Disease Notes : 1-6.

Larran, S., J. V. Bahima, G. D. Bello, E. Franco, and P. Balatti.  2015.  Colletotrichum siamense causing anthracnose in Bauhinia forficate subsp. pruinosa in Argentina.  Australasian Plant Disease Notes 10:7.

Prihastuti, H., L. Cai, H. Chen, E. H. C. McKenzie, and K. D. Hyde.  2009. Characterization of Colletotrichum species associated with coffee berries in northern Thailand. Fungal Diversity 39: 89-109.

Sharma, G., and B. D. Shenoy.  2014.  Colletotrichum fructicola and C. siamense are involved in chili anthracnose in India.  Archives of Phytopathology and Plant Protection 47:1179-1194.

Weir, B. S., P. R. Johnston and U. Damm.  2012.  The Colletotrichum gloeosporioides species complex.  Studies in Mycology, 73:115-180. DOI:10.3114/sim0011.

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

Plant Pathogens, Viruses and viroids

Hibiscus Latent Fort Pierce Virus (HLFPV)

California Pest Rating for
Hibiscus Latent Fort Pierce Virus (HLFPV)
Pest Rating: B
PEST RATING PROFILE
Initiating Event:

On September 10, 2015, diseased Abutilon sp. (mallow) plants showing chlorotic leaf spots were collected from a nursery in Solano County and sent by Solano County Agricultural officials to the CDFA Plant Pest Diagnostics Branch for analysis.  Tongyan Tian, CDFA plant pathologist identified two plant viruses namely, Abutilon mosaic virus and Hibiscus latent Fort Pierce virus associated with symptomatic Abutilon leaves.  Abutilon mosaic virus is known to be present within the State, however there have been no earlier reports of HLFPV from California.  The risk of infestation of HLFPV in California is evaluated and a permanent rating is herein proposed.     

History & Status:

Background:   Hibiscus latent Fort Pierce virus was first reported from Florida, USA, and was named according to the location and host from which it was isolated (Allen et al., 2005).  This virus belongs to the genus Tobamovirus which, until the discovery of HLFPV was known to comprise of three sub-groups that correspond to viral genome sequence and host range and include viruses that infect solanaceous plants, brassicas, and cucurbits or legumes.  Malvaceous plants had not been known as hosts for any of the tombamoviruses until the isolation of HLFPV as a new species from landscape plantings of the malvaceous plant hibiscus (Hibiscus rosinensis) in Florida. Subsequently, a limited survey conducted in Florida revealed that HLFPV is widespread in hibiscus and related species in the State’s landscapes.  HLFPV was also detected in H. rosasinensis in New Mexico, Thailand, Japan, and Indonesia (Adkins et al., 2003, 2006; Allen et al., 2005; Yoshida et al., 2014).  The current detection of HLFPV in California marks the first detection of this viral pathogen in the State.

Hosts: Natural hosts are mainly limited to Hibiscus spp. in the Malvaceae family, and include, H. rosasinensis (hibiscus), H. syriacus (rose of Sharon), H. coccineus (scarlett rosemallow), H. moscheutos (common rosemallow), Malvaviscus arboreus (Turk’s cap), (Adkins et al., 2003, 2006; Allen et al., 2005).  The detection HLFPV in Abutilon sp. from California marks a first record of a new host.

Experimental, mechanically-inoculated hosts include species within the family Solanaceae (Nicotiana glutinosa, N. rustica, and Petunia x hybrid with symptoms; N. benthamiana, N. debneyi, N. excelsior, and N. occidentalis – symptomless), Gomphrena globosa (symptomless), Chenopodium quinoa and C. amaranticolor (with symptoms), and species of the family Malvaceae including, Abelmoschus esculentus (okra), Gossypium sp., (cotton), Hibiscus cannabinus (kenaf – symptomless), Malvaviscus arboreus (Turk’s cap), and Hibiscus spp. (Adkins, et al., 2003, 2006).

Symptoms: Symptoms of HLFPV infection of hibiscus leaves include diffuse cholorotic spots and rings and an overall chorotic mottle (Adkins, 2003).  However, symptoms alone are not reliable for diagnosing HLFPV infections as hibiscus may be co-infected with additional viruses that often complex symptom expression.  Therefore, different diagnostic tools are necessary for accurate identification of the pathogen in diseased plant tissue.

Damage Potential: Presently, there are no reports of economic losses caused by HLFPV. Infected, symptomatic plants may cause loss in market value and sale of nursery plants.  However, hibiscus plants may be co-infected with more than one additional virus which may result in greater loss in plant production and value than expected by HLFPV infections alone.

Transmission: HLFPV is easily transmitted in hibiscus by common horticultural practices including mechanical transmission through contaminated pruning tools; infected plant cuttings, and nursery stock (Kamenova & Adkins, 2004; Adkins et al., 2006).

Worldwide Distribution: Asia: Japan, Indonesia, Thailand, North America: USA (California, Florida, New Mexico) (Adkins et al., 2003, 2006; Allen et al., 2005; Yoshida et al., 2014).

Official Control: None reported.  Currently Hibiscus latent Fort Pierce virus is rated Q in California.

California Distribution: Solano County (nursery).

California Interceptions:  There are no records of Hibiscus latent Fort Pierce virus detected in incoming plant shipments to California.

The risk Hibiscus latent Fort Pierce virus would pose to California is evaluated below.

Consequences of Introduction: 

1)  Climate/Host Interaction: Evaluate if the pest would have suitable hosts and climate to establish in California. Score:

– 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.

Risk is Medium (2) – Hibiscus latent Fort Pierce virus is likely to establish wherever hibiscus plants are grown mainly in warm and moist regions within California.   

2)  Known Pest Host Range: Evaluate the host range of the pest. Score:

– Low (1) has a very limited host range.
– Medium (2) has a moderate host range.
– High (3) has a wide host range.

Risk is Low (1) – Presently, the natural host range of Hibiscus latent Fort Pierce virus is mainly limited to Hibiscus spp. in the Malvaceae family.

3) Pest Dispersal Potential: Evaluate the natural and artificial dispersal potential of the pest. Score:

– 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.

Risk is High (3) – Hibiscus latent Fort Pierce virus, a tobamovirus, is readily transmitted mechanically through normal horticultural practices, particularly through contaminated pruning tools.  It has high reproduction within infected plants and is therefore,  also spread through the movement of infected plant cuttings, and nursery stock.

4) Economic Impact: Evaluate the economic impact of the pest to California using the criteria below. Score:

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.

– 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.

Risk is Medium (2) –The economic impact of  HLFPV  would particularly affect nursery productions where HLFPV-infected plants could lower crop value, result in reduction in sales, and increase in clean plant production costs.

5) Environmental Impact: Evaluate the environmental impact of the pest on California using the criteria below.

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.

Score the pest for Environmental Impact. Score:

– 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.

Risk is Medium (2) – The pathogen could significantly impact plantings of hibiscus in home/urban environments.

Consequences of Introduction to California for Hibiscus latent Fort Pierce virus

Add up the total score and include it here. (Score)

-Low = 5-8 points
–Medium = 9-12 points
-High = 13-15 points

Total points obtained on evaluation of consequences of introduction of HLFPV to California = Medium (10).

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. (Score)

-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.

Evaluation is Low (-1). Hibiscus latent Fort Pierce virus was detected in a nursery in Solano County, California.   

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:

The distribution of Hibiscus latent Fort Pierce virus within California is not fully known. Malvaceous host plants grown in private and commercial environments may be infected with a complex of viruses including HLFPV.  The proposed rating may change as more is learned about the presence and distribution of this virus in California.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Hibiscus latent Fort Pierce virus is B.

References:

Adkins, S., I. Kamenova, D. Achor, and D. J. Lewandowski.  2003.  Biological and molecular characterization of a novel tobamovirus with a unique host range.  Plant Disease 87: 1190-1196.

Adkins, S. I. Kamenova, P. Chiemsombat, C. A. Baker, and D. J. Lewandowski.  2006.  Tobamoviruses from hibiscus in Florida and beyond.  Proc. XIth IS on Virus Diseases in Ornamental, Editor C. A. Chang, Acta Hort. 722 ISHS 2006.

Allen, J. E., I. Kamenova, S. Adkins, and S. F. Hanson.  2005.  First report of Hibiscus latent Fort Pierce virus in New Mexico.  Plant Health Progress doi:10.1094/PHP-2005-0105-01-HN. http://www.plantmanagementnetwork.org/pub/php/brief/2005/hlfpv/.

Kamenova, I. and S. Adkins.  2004.  Transmission, in planta distribution, and management of Hibiscus latent Fort Pierce virus, a novel tobamovirus isolated from Florida hibiscus.  Plant Disease 88:674-679.

Yoshida, T., Y. Kitazawa, K. Komatsu, Y. Neriya, K. Ishikawa, N. Fujita, M. Hashimoto, K. Maejima, Y., Yamaji, and S. Namba.  2014.  Complete nucleotide sequence and genome structure of a Japanese isolate of hibiscus latent Fort Pierce virus, a unique tobamovirus that contains an internal poly(A) region in its 3’ end.  Archives of Virology 159:3161-3165.  DOI 10.1007/s00705-014-2175-3.

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

Erysiphe aquilegiae DC. 1815

California Pest Rating for
Erysiphe aquilegiae DC. 1815
Pest Rating:  C
PEST RATING PROFILE
Initiating Event:  

None.

History & Status:

Background:  The fungal pathogen, Erysiphe aquilegiae, originally named, Ischnochaeta aquilegiae (DC.) Sawada 1959 is the cause of powdery mildew disease that infects several species of plant hosts, including Aquilegia sp. (columbine), mainly in the family Ranunculaceae.

The pathogen is also known by other scientific names, including, E. aquilegiae var. aquilegiae, E. aquilegiae var. ranunculi, and E. ranunculi.  According to Uwe Braun (Professor, Martin-Luther-Universitӓt, Institut für Biologie, Halle, Germany: personal communication to Cheryl Blomquist, CDFA plant pathologist, email dated October 29, 2015), as currently circumscribed, E. aquilegiae is a complex of species that have yet to be clearly distinguished genetically.

During October, 2013, CDFA plant pathologist, Cheryl Blomquist, detected the powdery mildew, Erysiphe aquilegiae on Ranunculus sp. nursery stock that was grown in fields in San Luis Obispo County.  Additionally, there is an earlier report of the asexual (anamorph) stage of Erysiphe, namely, Oidium sp. on Aquilegia sp. from southern coastal counties in California (A. M. French, 1987, California Plant Disease Host Index 2nd edition) that indicates that this powdery mildew pathogen is widely distributed within the State.

Hosts:  Erysiphe aquilegiae comprises numerous ornamental and weed hosts of several genera of the family Ranunculaceae: Aconitum, Actaea, Anemone, Aquilegia, Caltha, Clematis (=Atragene), Consolida, Coptis, Delphinium, Nigella, Ranunculus, Thalictrum, and Trollius (Farr & Rossman, 2015).

Other hosts in different families have been reported based only on morphological analysis of the pathogen.  These records have not been genetically proven and therefore, are doubtful (Braun-Blomquist: personal communication, 2015).  They include Alnus japonica and A. pendula (Betulaceae), Breea setosa and Cirsium spp. (Asteraceae), Magnolia liliiflora (Magnolioideae), Paeonia lactiflora (Paeoniaceae), Quercus crispula and M. mongolica var. grosseserrata (Fagaceae), Swertia spp. (Gentianaceae), Urena lobata and U. lobata var. tomentosa (Malvaceae), and Catharanthus roseus (Apocynaceae) (Bolay, 2005; Farr & Rossman, 2015; Liberato & Cunnington, 2006).

Symptoms:  White to grayish powdery, mildew grows in spots or patches on young plant tissue or covers entire leaves and other plant organs. Mildew growth is most common on upper side of leaves, but may also be found on the underside of leaves, young shoots and stems, buds, flowers and young fruit. Pinhead-sized spherical chasmothecia (completely closed fungal fruiting bodies containing spores), initially white to yellow brown later turning black in color, develop singly or in clusters on older mildew.

Damage Potential:  In general, powdery mildews seldom kill their hosts however they reduce photosynthesis, utilize plant nutrients, increase respiration and transpiration, impair plant growth and reduce crop yields up to 40% (Agrios, 2005).

Disease Cycle:  Erysiphe aquilegiae is an obligate parasite that produces mycelium on the surface of plant tissues without invading it.  The pathogen obtains nutrients from the plant by producing haustoria (specialized absorbing organs) that grow into the epidermal cells of the plant. On the plant surface, the mycelium produces short conidiophores which in turn produce numerous chains of conidia that appear as white powdery coating.  These conidia are easily dispersed by air currents to cause new infections of host plants.  When conditions are unfavorable, the pathogen may produce chasmothecia containing ascospores.  The disease is common in cool or warm humid regions, but can also be common in warm and dry climates since their spores only require high relative humidity and not free-standing water to be released, germinate and cause infections (Agrios, 2005).  Once a plant is infected, mycelium continues to spread on a leaf surface regardless of the level of atmospheric moisture.

Worldwide Distribution: Erysiphe aquilegiae is circumglobally distributed.  Africa: South Africa; Asia: Armenia, China, Iran, Taiwan, Japan, Korea, Israel, USSR; Africa: South Africa; Europe: Lithuania, Ukraine, Romania, Estonia, Belarus, Switzerland, Austria, Czechoslovakia, Denmark, Finland, France, Germany, Hungary, Italy, Norway, Poland, Sweden, USSR, Yugoslavia, United Kingdom, Bulgaria, the Netherlands, Montenegro;  North America: Canada,  Mexico, USA (including Alaska, California); South America: Argentina; Oceania: Australia, New Zealand (Bolay, 2005; Braun, 1987; Farr & Rossman, 2015).

Official Control: No official control has been reported specifically for Erysiphe aquilegiae.  However, the order Erysiphales and Erysiphe spp. are included in the ‘Harmful Organism Lists’ for Australia and Nauru (Erysiphales) and Dominica, Grenada and Saint Lucia (Erysiphe spp., specifically for Mangifera spp. which is not a reported host for E. aquilegiae) (USDA-PCIT, 2015).  In California, the current rating for E. aquilegiae is ‘Z’ (which is given to a previously unrated organism of known economic and or environmental detriment but generally distributed within the state).

California Distribution:  Southern coastal counties: San Benito, Monterey, San Luis Obispo, Santa Barbara, Ventura, Los Angeles, Orange, and San Diego Counties.

California Interceptions: None reported.

The risk Erysiphe aquilegiae would pose to California is evaluated below:

Consequences of Introduction: 

1) Climate/Host Interaction: Evaluate if the pest would have suitable hosts and climate to establish in California. Score:

– 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.

Risk is Medium (2): Powdery mildew disease is common in cool or warm humid regions, but can also be common in warm and dry climates since the fungal spores only require high relative humidity and not free-standing water to be released, germinate and cause infections.  Once a plant is infected, mycelium continues to spread on a leaf surface regardless of the level of atmospheric moisture.

2) Known Pest Host Range: Evaluate the host range of the pest. Score:

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

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

Risk is High (3):  Hosts comprise ornamental and weed plants.  Most hosts of Erysiphe aquilegiae are in Ranunculaceae. Other doubtful hosts have also been reported in at least six other plant families.

3) Pest Dispersal Potential: Evaluate the natural and artificial dispersal potential of the pest. Score:

– 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.

Risk is High (3): The powdery mildew pathogen has high reproduction and, under conducive environmental conditions of high relative humidity and wind currents, has high dispersal potential.

4) Economic Impact: Evaluate the economic impact of the pest to California using the criteria below. Score:

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.

– 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.

Risk is Medium (2): In particular, nursery grown ornamental plants infected with the powdery mildew pathogen Erysiphe aquilegiae could result in lowered crop production and loss in sales.

5) Environmental Impact: Evaluate the environmental impact of the pest on California using the criteria below.

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.

Score the pest for Environmental Impact. Score:

– 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.

 Risk is Medium (2): Powdery mildew infection may significantly impact home/urban and ornamental plantings.  Endangered plant species are not affected.  Although five species of the thistle plant Cirsium spp. (Crystal Springs fountain thistle, San Luis Obispo thistle, Ashland thistle, Suisun thistle, and Surf thistle) and four species of larkspur Delphinium spp. (Baker’s larkspur, Cuyamaca larkspur, Golden larkspur, and San Clemente Island larkspur) are listed as endangered plants in California, these species are not reported hosts of E. aquilegiae.

Consequences of Introduction to California for Erysiphe aquilegiae:

Add up the total score and include it here. (Score)

-Low = 5-8 points

-Medium = 9-12 points

-High = 13-15 points

Total points obtained on evaluation of consequences of introduction to California = 12 (Medium).

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. (Score)

-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.

Evaluation is Medium (-3): Erysiphe aquilegiae has been detected in several southern coastal counties extending from San Benito to San Diego.  Given its high reproduction capability and suitable environmental conditions for its spread and infection, it is possible that the distribution of this powdery mildew extends further than currently reported.

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 Erysiphe aquilegiae is C.

References:

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

Bolay, A.  2005.  Les Oïdiums de Suisse (Erysiphacées).  Cryptogamica Helvetica, 20:38-40.

Braun U.  1987.  A monograph of the Erysiphales (powdery mildews).  Beihefte zur Nova Hedwigia, Heft 89, J. Cramer Berlin-Stuttgart 1987. Pgs 208-209.

Farr, D. F., and A. Y. Rossman.  2015.  Fungal Databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved October 22, 2015, from http://nt.ars-grin.gov/fungaldatabases/

Liberato, J. R., and J. H. Cunnington.  2006.  First record of Erysiphe aquilegiae on a host outside the Ranunculaceae.  Australasian Plant Pathology, 35:291-292.

USDA-PCIT.  2015.  United States Department of Agriculture, Phytosanitary Certificate Issuance & Tracking System (PCIT). https://pcit.aphis.usda.gov/PExD/faces/ViewPExD.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

Colletotrichum theobromicola Declr. 1905

California Pest Rating for
Colletotrichum theobromicola Declr. 1905
Pest Rating:  B
PEST RATING PROFILE
Initiating Event:  

On September 8, 2015 diseased Coleonema sp. (breath of heaven) seedlings exhibiting blight symptoms were collected from a nursery in Sacramento by Sacramento County Agricultural officials, and sent to the CDFA Plant Diagnostics Branch for diagnosis.  Suzanne Latham, CDFA plant pathologist identified the fungal fruit spot and anthracnose pathogen, Colletotrichum theobromicola as the cause for the disease. Subsequently, on September 14 and October 8, 2015, C. theobromicola was detected from Annona squamosa (sugar apple) fruit intercepted in shipments destined to private citizens and intercepted at the United States Postal Service by County officials in San Joaquin and Santa Clara Counties respectively.  Both shipments originated in Florida.  Consequently, all infected plant material was destroyed.  The risk of infestation of C. theobromicola in California is evaluated and a permanent rating is proposed.

History & Status:

Background:  Colletotrichum theobromicola is a distinct fungus species belonging to the vastly morphological and physiological variable C. gloeosporioides complex and is generally identified from other species of the complex only with DNA sequences. The species: C. fragariae, C. gloeosporioides f. stylosanthis, C. gloeosporioides f. stylosanthis “f. sp. stylosanthis”, and C. gloeosporioides f. stylosanthis “f. sp. guianensis’ are genetically similar to, and synonyms of C. theobromicola (Weir et al, 2012).

Colletotrichum fragariae (synonym of C. theobromicola) has been previously reported from strawberry plants in California (Gunnell & Gubler, 1992), however, that report was based only on morphological analysis of the species.  So, while there is the possibility that C. theobromicola may have been present in California prior to the CDFA detections mentioned above, its presence cannot be assumed or confirmed without genetic analysis. The recent detections of the C. theobromicola by CDFA constitute its first official State record in California.

Hosts: Colletotrichum theobromicola has been reported on different hosts from different countries:  Acca sellowiana (pineapple guava), Annona diversifolia (Ilama fruit), Annona squamosa (sugar/custard apple), Buxus microphylla var. japonica (Japanese boxwood), Cassia obtusifolia (sicklepod), coffea arabica (Arabian coffee), Coffea sp., Coleonema sp. (breath of heaven)( CDFA detection), Cyclamens persicum (Persian cyclamen), Fragaria ananassa (strawberry), Fragaria sp., F. chiloensis (coastal strawberry), F. vesca (wild strawberry), F. virginiana (woodland strawberry), Limonium sp. (statice), Olea europaea (olive), Potentilla canadensis (dwarf cinquefoil), Punica granatum (pomegranate),  Quercus sp. (oak), Stylosanthes guianensis (stylo, Brazilian lucerne), S. viscosa (poorman’s friend), Theobroma cacao (cacao, cocoa tree) (Farr & Rossman, 2015; Weir et al., 2012).

Symptoms:  Colletotrichum theobromicola causes leaf and fruit spots.  Generally, Colletotrichum-infected host plants exhibit symptoms of anthracnose which include dark brown leaf, stem and fruit spots and wilting of leaves which often result in dieback and reduction in plant quality.  The pathogen causes anthracnose disease of strawberry with symptoms that include crown rot, fruit rot and stolon lesions (Gunnell & Gubler, 1992).

Damage Potential:  Anthracnose disease caused by Colletotrichum theobromicola can result in reduced plant quality and growth, fruit production and marketability.  Estimates of yield/crop loss due to this pathogen have not been reported.  Nursery production of potted host plants or in greenhouses are particularly at risk as nursery conditions are often conducive to infection by Colletotrichum species.  In cultivated fields, disease development may be sporadic as it is affected by levels of pathogen inoculum and environmental conditions.

Disease Cycle:  It is likely that Colletotrichum theobromicola has a similar life cycle to that of other Colletotrichum species and survives between crops during winter as mycelium on plant residue in soil, on infected plants, and on seeds.  During active growth, the pathogen produces masses of hyphae (stromata) which bear conidiophores, on the plant surface. Conidia (spores) are produced at the tips of the conidiophores and disseminated by wind, rain, cultivation tools, equipment, and field workers.   Conidia are transmitted to host plants.  Humid, wet, rainy weather is necessary for infection to occur.  These requirements in particular may limit the occurrence of the pathogen in California fields and subsequently, the pathogen may be more of a problem under controlled environments of greenhouses.  Conidia germinate, penetrate host tissue by means of specialized hyphae (appresoria) and invade host tissue.

Transmission:  Wind, wind-driven rain, cultivation tools, and human contact.

Worldwide Distribution:  Colletototrichum theobromicola is widely distributed in tropical and subtropical region worldwide.  Africa: Nigeria; Asia: India, Israel, Japan; North America: Mexico, USA (California, Florida, Indiana, Louisiana, Michigan, Mississippi, New York, North Carolina, South Carolina, Virginia), Cuba, Panama; South America: Brazil, Uruguay; Australia; New Zealand (CABI, 2015; Farr & Rossman, 2015; Gunnell & Gubler, 1992; Weir et al., 2012).

Official Control:  In California C. theobromicola is an actionable, Q-rated pathogen, and infected plant material is subject to destruction or rejection.

California Distribution: Colletotrichum theobromicola is not established in California (see “Initiating Event”).

California Interceptions: Two interceptions of Colletotrichum theobromicola-infected sugar apple fruit (see ‘Initiating event’).

The risk Colletotrichum theobromicola would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: Evaluate if the pest would have suitable hosts and climate to establish in California. Score:

– 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.

Risk is Medium (2) – Similar to other species of Colletotrichum, C. theobromicola requires humid, wet, rainy weather for conidia to infect host plants. This environmental requirement may limit the ability of the pathogen to fully establish and spread under dry field conditions in California.

2) Known Pest Host Range: Evaluate the host range of the pest. Score:

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

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

Risk is Moderate (2) – Colletotrichum theobromicola has a moderate range of diverse hosts generally common in tropical and sub tropical regions. Of those hosts,strawberry, certain ornamentals, olive and oak are among the economically important hosts in California.

3) Pest Dispersal Potential: Evaluate the natural and artificial dispersal potential of the pest. Score:

– 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.

Risk is High (3) – The pathogen has high reproductive potential and conidia are produced successively.  They are transmitted by wind, wind-driven rain, cultivation tools, and human contact however conidial germination and plant infection require long, wet periods.

4) Economic Impact: Evaluate the economic impact of the pest to California using the criteria below. Score:

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.

– 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.

Risk is High (3) – Productions of strawberry fruit and nursery grown ornamental plants, in particular, can be limited by their susceptibility to anthracnose under wet conditions. Therefore, under suitable climates, the pathogen could lower plant growth, fruit production and value and trigger the loss of markets.

5) Environmental Impact: Evaluate the environmental impact of the pest on California using the criteria below.

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.

Score the pest for Environmental Impact. Score:

– 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.

Risk is Medium (2) – The pathogen could significantly impact cultural practices or home garden plantings.

Consequences of Introduction to California for Colletotrichum theobromicola:

Add up the total score and include it here. (Score)

-Low = 5-8 points

-Medium = 9-12 points

-High = 13-15 points

Total points obtained on evaluation of consequences of introduction of Colletotrichum theobromicola to California = (12).

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. (Score)

-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.

Evaluation is not established (0).  Colletotrichum theobromicola is not established in California. 

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 = 12.

Uncertainty:

None.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for the anthracnose pathogen, Colletotrichum theobromicola is B.

References:

CABI.  2015.  Colletotrichum fragariae (anthracnose of strawberry) full datasheet report.  Crop Protection Compendium.  www.cabi.org/cpc/

Farr, D. F., & A. Y. Rossman.  Fungal databases, systematic mycology and microbiology laboratory, ARS, USDA. Retrieved April 7, 2015, from

http://nt.ars-grin.gov/fungaldatabases/

Gunnell, P. S., and W. D. Gubler.  1992.  Taxonomy and morphology of Colletotrichum species pathogenic to strawberry.  Mycologia 84:157-165.

Weir, B. S., P. R. Johnston, and U. Damm.  2012.  The Colletotrichum gloeosporioides species complex.  Studies in Mycology, 73:115-180. DOI:10.3114/sim0011.

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

Colletotrichum queenslandicum B. Weir & P. R. Johnst. 2012

California Pest Rating for
Colletotrichum queenslandicum B. Weir & P. R. Johnst. 2012
 Pest Rating:  B
PEST RATING PROFILE
Initiating Event:  

On October 29, 2015 California Dog Teams intercepted Persea americana (avocado) fruit at parcel distribution facilities in Los Angeles and Santa Clara Counties.  The shipments had originated in Florida and Puerto Rico and were destined to private citizens in Los Angeles and Santa Clara Counties accordingly.  Diseased avocado fruit with necrotic spots were collected by County Agricultural officials, and sent to the CDFA Plant Diagnostics Branch for diagnosis.  Suzanne Latham, CDFA plant pathologist identified the fungal fruit spot and anthracnose pathogen, Colletotrichum queenslandicum as the cause for the disease. The identity of the associated pathogen was later confirmed by USDA National Identification Services at Beltsville, Maryland, and marked the first detection of C. queenslandicum in continental USA.  [According to USDA APHIS, the first US domestic detection of C. queenslandicum was reported from Hawaii on October 19, 2015.]  Consequent to the California detection, all infected plant materials were destroyed. The risk of infestation of C. queenslandicum in California is evaluated and a permanent rating is proposed.

History & Status:

Background:  Colletotrichum queenslandicum is a distinct fungus species belonging to the vastly morphological and physiological variable C. gloeosporioides and is genetically identified from other species of the complex (Weir et al, 2012).  The species was originally described in 1965 as C. gloeosporioides var. minus Simmonds from Carica papaya (papaya) in Queensland, Australia.  The new name, C. queenslandicum was proposed by Weir and Johnston in 2012.

Hosts: Colletotrichum queenslandicum is known from few different hosts in different countries: Carica papaya, Carica sp. Persea americana, and Passiflora edulis (Australia); Coffea sp. (Fiji) (Farr & Rossman, 2015; James et al., 2014; Vieira et al., 2014; Simmonds, 1965).

Symptoms:  Colletotrichum queenslandicum causes leaf and fruit spots.  Generally, Colletotrichum-infected host plants exhibit symptoms of anthracnose which include dark brown leaf, stem and fruit spots and wilting of leaves which often result in dieback and reduction in plant quality.

Damage Potential:  Anthracnose disease caused by Colletotrichum queenslandicum can result in reduced plant quality and growth, fruit production and marketability.  Estimates of yield/crop loss due to this pathogen have not been reported.  Nursery productions of papaya and avocado plants are particularly at risk as nursery conditions are often conducive to infection by Colletotrichum species.  In open fields, disease development may be sporadic as it is affected by levels of pathogen inoculum and environmental conditions.

Disease Cycle:  It is likely that Colletotrichum queenslandicum has a similar life cycle to that of other Colletotrichum species and survives between crops during winter as mycelium on plant residue in soil, on infected plants, and on seeds.  During active growth, the pathogen produces masses of hyphae (stromata) which bear conidiophores, on the plant surface. Conidia (spores) are produced at the tips of the conidiophores and disseminated by wind, rain, cultivation tools, equipment, and field workers.   Conidia are transmitted to host plants.  Humid, wet, rainy weather is necessary for infection to occur.  These requirements in particular may limit the occurrence of the pathogen in California fields and subsequently, the pathogen may be more of a problem under controlled environments of greenhouses.  Conidia germinate, penetrate host tissue by means of specialized hyphae (appresoria) and invade host tissue.

Transmission:  Wind, wind-driven rain, cultivation tools, and human contact.

Worldwide Distribution:  Colletotrichum queenslandicum is distributed in Australia and Fiji (Farr & Rossman, 2015; James et al., 2014; Vieira et al., 2014; Simmonds, 1965).

Official Control:  In California C. queenslandicum is an actionable, Q-rated pathogen, and infected plant material is subject to destruction or rejection.

California Distribution: Colletotrichum queenslandicum is not established in California (see “Initiating Event”).

California Interceptions: There have been two reported interceptions of Colletotrichum queenslandicum-infected avocado fruit. (see ‘Initiating event’).

The risk Colletotrichum queenslandicum would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: Evaluate if the pest would have suitable hosts and climate to establish in California. Score:

– 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.

Risk is Medium (2) – Similar to other species of Colletotrichum queenslandicum requires humid, wet, rainy weather for conidia to infect host plants. This environmental requirement and narrow host range may limit the ability of the pathogen to fully establish and spread under dry field conditions in mainly in southern California.

2) Known Pest Host Range: Evaluate the host range of the pest. Score:

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

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

Risk is Low (1) – Colletotrichum queenslandicum has a limited host range comprising mainly of avocado, papaya, coffee and purple Granadilla (Passiflora edulis).  The Latter two hosts are not grown in California and avocado and papaya have limited productions mainly in the southern regions of the State.

3) Pest Dispersal Potential: Evaluate the natural and artificial dispersal potential of the pest. Score:

– 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.

Risk is High (3) – The pathogen has high reproductive potential and conidia are produced successively.  They are transmitted by wind, wind-driven rain, cultivation tools, and human contact however conidial germination and plant infection require long, wet periods.

4) Economic Impact: Evaluate the economic impact of the pest to California using the criteria below. Score:

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.

– 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.

Risk is Medium (2) –Anthracnose-infected papaya and avocado fruit may result in lower crop value and market loss.  Its economic impact is evaluated as a medium risk.   

5) Environmental Impact: Evaluate the environmental impact of the pest on California using the criteria below.

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.

Score the pest for Environmental Impact. Score:

– 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.

Risk is Medium (2) – The pathogen could significantly impact backyard productions of papaya and avocado wherever grown in California.

Consequences of Introduction to California for Colletotrichum queenslandicum:

Add up the total score and include it here. (Score)

-Low = 5-8 points

-Medium = 9-12 points

-High = 13-15 points

Total points obtained on evaluation of consequences of introduction of Colletotrichum queenslandicum to California = (10).

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. (Score)

-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.

Evaluation is not established (0).  Colletotrichum queenslandicum is not established in California. 

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 the anthracnose pathogen, Colletotrichum queenslandicum is B.

References:

Farr, D. F., & A. Y. Rossman.  Fungal databases, systematic mycology and microbiology laboratory, ARS, USDA. Retrieved April 7, 2015, from

http://nt.ars-grin.gov/fungaldatabases/

James, R.S., J.  Ray, Y. P. Tan and R. G. Shivas.  2014.  Colletotrichum siamense, C. theobromicola, and C. queenslandicum from several plant species and the identification of C. asianum in the Northern Territory, Australia. Australasian Plant Disease Notes : 1-6.

Simmonds, J. H.  1965.  A study of the species of Colletotrichum causing ripe fruit rots in Queensland.  Queensland Journal of Agricultural and Animal Sciences 22: 437-459.

Vieira, W.A.S., S. J. Michereff, M. A. de Morais, Jr., K. D. Hyde and M. P. S. Camara.  2014. Endophytic species of Colletotrichum associated with mango in northeastern Brazil. Fung. Diversity 67: 181-202.

Weir, B. S., P. R. Johnston and U. Damm.  2012.  The Colletotrichum gloeosporioides species complex.  Studies in Mycology, 73:115-180. DOI:10.3114/sim0011.

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

Geosmithia pallida (G. Sm.) M. Kolarík, Kubátová & Paotová

California Pest Rating for
Geosmithia pallida (G. Sm.) M. Kolarík, Kubátová & Paotová
 Pest Rating:  C
PEST RATING PROFILE
Initiating Event:

During August 2014, The CDFA Pathology Laboratory received official samples of diseased oak trees exhibiting symptoms of foaming cankers, collected from residential and commercial landscape sites in Marin and Napa counties.  The fungal pathogen Geosmithia pallida, causing foamy bark canker disease, was identified by Suzanne Latham, CDFA Plant Pathologist.  Within a few weeks of this detection, G. pallida was also detected in official oak samples collected in Santa Clara and El Dorado counties.  Prior to these official reports, the foamy bark canker disease has been known to exist throughout southern California extending to Monterey County.   The pathogen has not been previously rated and therefore, the need for a definite rating is necessitated and proposed.

History & Status:

Background:  Researchers at the Department of Plant Pathology, University of California, Riverside, have observed since 2012 decline of coast live oak (Quercus agrifolia) throughout urban landscapes in southern California (Lynch, et al., 2014). The fungus Geosmithia pallida was determined to be the cause of the observed symptoms which were successfully reproduced in pathogenicity tests on detached coast live oak shoots and in 2014, Lynch et al. provided the first report of G. pallida causing foamy bark canker on coast live oak in California and the USA.  They recovered the fungal species from symptomatic plant tissues associated with the western oak bark beetle Pseudopityophthorus pubipennis.  The western oak bark beetle is native to California and common as a secondary agent that readily attacks stressed plants.  It has not been previously associated with disease; however, cryptic species may be common among bark and ambrosia beetles (Lynch et al., 2014). The beetle burrows through the tree bark forming shallow tunnels below the bark and across the grain of the wood.  Eggs are laid within the tunnels and on hatching, the developing larvae form tunnels at right angles to their main tunnel and mostly within the inner bark or phloem close to the surface.  The fungus is dry-spored and occurs in the tunnels or galleries built by the beetles. Once insect larvae develop, they carry fungal spores and fly to other uninfected trees thereby spreading the fungus.

The fungal pathogen was originally placed in the genus Penicillium as the species, P. palladium which was later considered a synonym of Geosmithia putterillii (Pitt, 1979).  The latter species is a complex group of species comprising three genetically isolated cryptic species with worldwide distribution (Kolařík et al., 2004). Several isolates have been acquired from wood or subcorticolous insects.  In 2004, based on molecular and morphological analyses, Kolařík and others separated G. pallida from the G. putterillii species complex.

Hosts: Quercus agrifolia (coast live oak), Q. rubra (northern red oak), Q. wislizenii (interior live oak).

Symptoms:  Symptoms of G. pallida infection occur on the trunk and primary branches of trees and include wet discoloration seeping through entry holes caused by the western oak bark beetle.  Necrotic phloem and xylem tissue is apparent beneath the outer bark.  Multiple beetle entry holes may also be apparent on a single tree.  As the disease advances, a cream to reddish sap may ooze from the entry hole, followed by a prolific foamy liquid which may run down the trunk for about 2 feet.  The symptoms may be confused with those caused by Fusarium dieback/Polyphagous Shot Hole Borer; however, the size of the entry hole associated with foamy canker is smaller than those made by the Polyphagous Shot Hole Borer (Lynch et al., 2014).  In Europe, in laboratory plant growth culture tests using garden cress plants, G. pallida inhibited root growth by 25% whereas stem growth was almost unimpaired (Čižková et al., 2005).

Damage Potential:  Symptom associated with foamy bark canker disease on coast live oak result in branch dieback and tree death.

Transmission:  The fungal pathogen is associated with the western oak bark beetle and transmitted from infected to non-infected trees during movement and feeding by the beetle.  The fungus is also spread to uninfected sites through the movement of infected wood, such as firewood, and contaminated pruning and cutting equipment.

Worldwide Distribution:  Geosmithia pallida has a worldwide distribution (Kolařík et al., 2004).

Official Control:  There are no reports of official control of the fungal pathogen.

California Distribution: Los Angeles, Orange, Riverside, Santa Barbara, Ventura and Monterey counties (Lynch et al., 2014).  CDFA official samples collected from El Dorado, Napa, Marin and Santa Clara counties were positive for Geosmithia pallida (see ‘Initiating Event’).

California Interceptions:  Geosmithia pallida has not been intercepted in imported official shipments to California.

The risk Geosmithia pallida would pose to California is evaluated below.

Consequences of Introduction: 

 1) Climate/Host Interaction: Evaluate if the pest would have suitable hosts and climate to establish in California. Score:

– 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.

Risk is High (3). Geosmithia pallida is already established in ten counties.

2) Known Pest Host Range: Evaluate the host range of the pest. Score:

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

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

Risk is Low (1).   Presently the pathogen has been observed causing decline and death of coast live oak in association with the western oak bark beetle.  In California, coast live oak occurs in the coastal ranges from north central to southern counties. So, even though Geosmithia pallida has been found affecting one host, the latter as well as other host species of oak are relatively wide spread throughout the State.

 3) Pest Dispersal Potential: Evaluate the natural and artificial dispersal potential of the pest. Score:

– 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.

Risk is High (3).  The fungal pathogen is artificially spread by movement of its associated insect vector and infected wood. The western oak bark beetle vector is native to California and is capable of moving and finding habitation throughout the State.

4) Economic Impact: Evaluate the economic impact of the pest to California using the criteria below. Score:

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.

– 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.

Risk is High (3).  Foamy bark canker disease caused by Geosmithia pallida could result in tree decline and death of coast live oak trees.  Currently, there are no known control measures against this pathogen. Early detection is noted as being crucial and could lead to pruning back infected branches, and other cultural treatments.  Regulations against movement of oak firewood could be necessary and this could directly trigger loss of markets. Plus the pathogen is easily vectored by the native western oak bark beetle.   

5) Environmental Impact: Evaluate the environmental impact of the pest on California using the criteria below.

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.

Score the pest for Environmental Impact. Score:

– 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.

 Risk is High (3).  The decline of infected oak trees could have significant environmental impact by disrupting natural communities, critical habitats or changing the ecosystem process. The potential loss of coast live oak could seriously threaten the conservation of the host plant thereby negatively impacting the 2001 California Oak Woodlands Conservation Act approved by California State Legislature.

Consequences of Introduction to California for Geosmithia pallida:

Add up the total score and include it here. (Score)

-Low = 5-8 points

-Medium = 9-12 points

-High = 13-15 points

Total points obtained on evaluation of consequences of introduction of Geosmithia pallida to California = (13).

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. (Score)

-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.

Evaluation is High (-3). The pathogen has been reported in more than two contiguous or non-contiguous counties with suitable host and climate.

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:

The pathogen is capable of spreading throughout California wherever suitable host and climate are present.  Since its detection in the southern counties it has spread to the central coastal region.  With the widespread distribution of the host plant and the associated western oak bark beetle vector, there is the possibility for the foamy bark canker disease to continue to spread statewide.  Further statewide survey and reports would be necessary to confirm this probability.  With further spread of the pathogen, the numeric score assessed here is not expected to change by much, thereby, strengthening its proposed ‘C’ rating.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for the Foamy Bark Canker Disease pathogen, Geosmithia pallida is C.

References:

Čížková, D., P. Šrůtka, M. Kolařík, A. Kubátová and S. Pažoutová.  2005.  Assessing the pathogenic effect of Fusarium, Geosmithia and Ophiostoma fungi from broad-leaved trees.  Folia Microbiologica, 50:59-62.

Kolařík, M., A. Kubátová, S. Pažoutová and Petr Šrůtka.  2004.  Morphological and molecular characterization of Geosmithia putterillii, G. pallida comb. nov. and G. flava sp. nov., associated with subcorticolous insects.  Mycological Research 108: 1053-1069.

Lynch, S. C., D. H. Wang, J. S. Mayorquin, P. Rugman-Jones, R. Southamer and A. Eskalen.  2004.  First report of Geosmithia pallida causing foamy bark canker, a new disease on coast live oak (Quercus agrifolia) in association with Pseudopityophthorus pubipenis (western oak bark beetle, Coleoptera: Curculionidae: Scolytinae) in California.  Plant Disease “First Look” paper posted 05/21/2014: http://dx.doi.org/10.1094/PDIS-03-14-0273-PDN.

Lynch, S. P., R. Rugman-Jones, R. Southamer and A. Eskalen.  (Not dated).  Pest Alert:  Geosmithia pallida and Western Oak Bark Beetle (Pseudopityophthorus pubipenis) causing foamy bark canker disease on coast live oak (Quercus agrifolia) in California.  University of California, Riverside.

Pitt, J. I. (1979) Geosmithia gen. nov. for Penicillium lavendulum and related species. Canadian Journal of Botany 57: 2021–2030.

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

Colletotrichum cymbidiicola Damm, P. F. Cannon, Crous, P. R. Johnst. & B. Weir, 2012

California Pest Rating for
Colletotrichum cymbidiicola Damm, P. F. Cannon, Crous, P. R. Johnst. & B. Weir, 2012
Pest Rating: B
PEST RATING PROFILE
Initiating Event:    

In April 2014, during an inspection of a nursery in San Diego County, California, Pat Nolan, plant pathologist, San Diego County, observed black spots on leaves of greenhouse-grown cymbidium orchids and submitted symptomatic foliar samples to the CDFA Plant Pathology Laboratory for pathogen diagnosis.  Suzanne Latham, plant pathologist, CDFA analyzed the samples and detected Colletotrichum cymbidiicola in cultures of the symptomatic leaves.  The identity of the associated pathogen was later confirmed by the USDA APHIS National Identification Services.  This detection marked a first record of C. cymbidiicola in the USA (Bethke, 2014).  Follow-up samples collected in June and August from the same nursery, also tested positive for C. cymbidiicola.  Subsequently, the nursery destroyed symptomatic plants and administered sanitary and fungicidal treatment measures to protect remaining plants from future infections.  Trace-back investigations revealed that the San Diego orchids originated in a nursery in Humboldt County.  However, C. cymbidiicola was not detected in orchid samples collected from the Humboldt nursery greenhouse.  A few months later, in June 2014, C. cymbidiicola was detected again in cymbidium orchids in a small, residential nursery in Santa Clara County, however, no trace-back information was available.   Recently, on May 7, 2015, more C. cymbidiicola was detected in orchids from the original nursery in San Diego County.    Therefore, there is a need to reevaluate the current temporary pest rating of C. cymbidiicola for the proposal of a permanent rating.

History & Status:

Background:  Colletotrichum cymbidiicola is a fungus species belonging to the complex species group C. boninense which was originally described in 2003 as a segregate of the vastly morphological and physiological variable C. gloeosporioides complex (CABI, 2014; Morikwaki et al., 2003).  In the past, isolates of C. boninense were often identified as C. gloeosporioides.  However, after segregation from C. gloeosporioides, researchers found that C. boninense actually comprised of a complex of several species and by 2012, through molecular phylogenetic analyses of 86 strains of C. boninense, Damm et al. (2012) were able to recognize 18 species within the C. boninense complex including C. cymbidiicola based on DNA sequence data and morphology.  Colletotrichum cymbidiicola is associated with orchids and is specific at plant genus level.

Hosts: Cymbidium spp. (orchids) (Damm et al., 2012).

Symptoms:  Anthracnose symptoms are expressed as dark spots or lesions in infected orchid leaves, petioles and blossoms.  Initial symptoms include brown discolorations which are irregularly shaped sunken lesions that turn to dark brown with concentric brownish black fruiting bodies (acervuli).  Leaf wilting may occur often resulting in dieback and reduction in plant quality.  As in orchids infected with Colletotrichum gloeosporioides, symptoms may be most common on orchid leaves when stressed plants are damaged by cold and hot temperatures, sun, wind, chemicals and mechanical damage.

Damage Potential:  Anthracnose disease caused by Colletotrichum cymbidiicola can result in reduced plant quality and growth.  Estimates of yield/crop loss due to this pathogen have not been reported although severe outbreaks of orchid anthracnose have been reported in India (Chowdappa, et al., 2014).  Nursery production of potted host plants or in greenhouses are particularly at risk as nursery conditions are often conducive to infection by Colletotrichum species.  In cultivated fields, disease development may be sporadic as it is affected by levels of pathogen inoculum and environmental conditions.

Disease Cycle:  It is likely that Colletotrichum cymbidiicola has a similar life cycle to that of other Colletotrichum species and survives between crops during winter as mycelium on plant residue in soil, on infected plants, and on seeds.  During active growth, the pathogen produces masses of hyphae (stromata) which result in fruiting bodies (acervuli) that bear conidiophores, on the plant surface. Conidia (spores) are produced at the tips of the conidiophores and disseminated by wind, rain, cultivation tools, equipment, and field workers.   Conidia are transmitted to host plants.  Humid, wet, rainy weather is necessary for infection to occur.  These requirements in particular may limit the occurrence of the pathogen in California fields and subsequently, the pathogen may be more of a problem under controlled environments of greenhouses.  Condia germinate, penetrate host tissue by means of specialized hyphae (appresoria) and invade host tissue.

Transmission:  Wind, wind-driven rain, cultivation tools, and human contact.

Worldwide Distribution:  Australia, India, Japan, New Zealand, USA (California) (Chowdappa et al., 2014; Damm, et al., 2012; Farr & Rossman, 2015).

Official Control:  Colletotrichum cymbidiicola is considered a new record in North America and reportable to the USDA.

California Distribution: San Diego and Santa Clara Counties (see ‘Initiating Event’).

During the 1980s, CDFA plant pathologists identified C. gloeosporioides in Cymbidium sp. (Alex French, California Plant Disease Host Index 2nd edition).  The site of detection generally includes the southern coastal counties. Details of that specific record are not currently available.  At that time specific molecular diagnostic tests were not available to enable the distinction of C. cymbidiicola.  It is, therefore, possible that this detection may have included C. cymbidiicola. No eliminative action would have been taken against C. gloeosporioides as the species is known to be widespread in California.  However, since that detection and until the 2014-2015 detections noted above in ‘Initiating Events’ there have been no reports of Colletotrichum sp. on cymbidium orchids in California.

California Interceptions:  Colletotrichum cymbidiicola has not been intercepted in quarantine plant shipments imported to California.

The risk Colletotrichum cymbidiicola would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: Evaluate if the pest would have suitable hosts and climate to establish in California. Score:

– 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.

Risk is Medium (2) – Similar to other species of Colletotrichum, C. cymbidiicola requires humid, wet, rainy weather for conidia to infect host plants. This environmental requirement may limit the ability of the pathogen to fully establish and spread under dry field conditions in California. On the other hand, the pathogen could establish in limited regions with conducive climates within California. Of particular importance is the ability for  C. cymbidiicola to effectively infect and spread to host plants grown under conducive climate conditions in nurseries.

2) Known Pest Host Range: Evaluate the host range of the pest. Score:

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

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

Risk is Low (1) – Presently the host range of Colletotrichum cymbidiicola is limited to orchids, Cymbidium sp.

3) Pest Dispersal Potential: Evaluate the natural and artificial dispersal potential of the pest. Score:

– 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.

Risk is High (3) – The pathogen has high reproductive potential and conidia are produced successively.  They are transmitted by wind, wind-driven rain, cultivation tools, and human contact however conidial germination and plant infection require long, wet periods.

4) Economic Impact: Evaluate the economic impact of the pest to California using the criteria below. Score:

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.

– 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.

Risk is High (3) – Under suitable climates, the pathogen could lower plant growth and value and trigger the loss of markets.

5) Environmental Impact: Evaluate the environmental impact of the pest on California using the criteria below.

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.

Score the pest for Environmental Impact. Score:

– 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.

Risk is Medium (2) – The pathogen could significantly impact cultural practices, home or ornamental plantings of orchids.

Consequences of Introduction to California for Colletotrichum cymbidiicola:

Add up the total score and include it here. (Score)

-Low = 5-8 points

–Medium = 9-12 points

-High = 13-15 points

Total points obtained on evaluation of consequences of introduction of Colletotrichum cymbidiicola to California = (11).

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. (Score)

-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.

Evaluation is Low (-1).  Colletotrichum cymbidiicola has been found in nursery greenhouses in two coastal counties: San Diego and Santa Clara.

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:

The detection and distribution of Colletotrichum cymbidiicola in other orchid-growing California counties is not known.  Subsequent results from those detections may alter the proposed rating for the pathogen.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for the anthracnose pathogen, Colletotrichum cymbidiicola is B.

References:

Bethke, J. A.  2014.  First detection of Colletotrichum cymbidiicola in California and water supply update.  UCNFA News, University of California, Division of Agriculture and Natural Resources.  http://ucanr.edu/sites/UCNFAnews/Regional_Report_San_Diego_and_Riverside_Counties/Summer_2014__First_detection_of_Colletotrichum_cymbidiicola_in_California/# .

Chowdappa, P., C. S. Chethana,  R. P. Pant and P. D. Bridge.  2014.  Multilocus gene phylogeny reveals occurrence of Colletotrichum cymbidiicola and C. cliviae on orchids in North East India.  Journal of Plant Pathology, 96:327-334.

Damm, U., P. F. Cannon, J. H. C. Wouldenberg, P. R. Johnston, B. S. Weir, Y. P. Tan, R. G. Shivas and P. W. Crous.  2012.  The Colletotrichum boninense species complex.  Studies in Mycology 73:1-36; www.studiesinmycology.org .

Farr, D. F., & A. Y. Rossman.  Fungal databases, systematic mycology and microbiology laboratory, ARS, USDA. Retrieved April 7, 2015, from

http://nt.ars-grin.gov/fungaldatabases/ .

Kitterly, W. R., and A. P. Keinath.  1996.  Fungal disease of aerial parts: Anthracnose. In ‘Compendium of Cucurbit Diseases’.  Edited by T. A. Zitter, D. L. Hopkins, and C. E. Thomas, APS Press The American Phytopathological Society Minnesota, USA, p. 24-25.

Moriwaki, J., T. Sato and T. Tsukiboshi.  2003.  Morphological and molecular characterization of Colletotrichum boninense sp. nov. from Japan.  Mycoscience 44:47-53.

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

Posting by ls

Plant Pathogens, Viruses and viroids

Tomato Yellow Leaf Curl Virus (TYLCV)

California Pest Rating for
Tomato Yellow Leaf Curl Virus (TYLCV)
Pest Rating: B
PEST RATING PROFILE
Initiating Event: 

The risk of infestation of Tomato yellow leaf curl virus (TYLCV) in California is evaluated and a permanent rating is proposed.

History & Status:

Background:    During the early 1960s in Israel, Tomato yellow leaf curl virus was the name first given to diseased tomatoes that in 1959 were found to be infected by an agent identified as a whitefly-transmitted viral agent in the Jordan Valley, Israel.  Since then and in less than 25 years, TYLCV spread worldwide.    TYLCV belongs to the genus Begomovirus in the Family Geminiviridae – which includes whitefly transmitted viruses.  The pathogen is accurately identified by the analysis of DNA sequences. The Israel strain was isolated in 1988 and was the first one to be sequenced in 1991. Sequence comparisons of different geographical isolates revealed that TYLCV is actually a complex of begomovirus species that affect tomato.  Subsequently, begomoviruses affecting tomato were separated into several groups and named accordingly.  Tomato yellow leaf curl virus is the name of the virus isolated in Israel (CABI, 2014; Nakhla & Maxwell, 1998; Fauquet et al., 2000). Seven different species belonging to the Tomato yellow leaf curl virus complex have been identified.

Tomato yellow leaf curl virus was identified in 2007 for the first time from infected tomato plants grown in a greenhouse in Brawley, Imperial County, California (Rojas et al., 2007).  Since then the pathogen has been detected in commercial fields, nurseries and private residences within Imperial and Riverside counties.

Hosts: Solanum lycopersicum (tomato) is the major host.  Other hosts include diagnostic experimental plant species belonging to several families: Datura stramonium, Lycopersicon esculentum, Nicotiana glutinosa, N. benthamiana, Phaseolus vulgaris, Petunia hybrida, and Eustoma grandiflorum (lisianthus).   Other cultivated minor hosts include abelmoschus esculentus (okra), C. annum (bell pepper), C. frutescens (cayenne/chili pepper), Nicotiana tabacum (tobacco), Physalis philadelphica (tomatillo), and Vigna unguiculata (cowpea).  Weeds and other wild hosts include Acalypha australis, Artemisia annua, Ageratum conyzoides (billy goat weed), Convolvulus (morning glory), Chenopodium murale (nettleleaf goosefoot), Cuscuta europaea (European dodder), Datura stramonium (jimsonweed), Malva parviflora (pink cheeseweed), Moringa oleifera (horse-radish tree), Sida acuta (sida), Solanum elaegniflolium (silverleaf nightshade) and S. nigrum (black nightshade) (CABI, 2014; VIDE, 1996; EPPO 2014).

In a survey in Cyprus, Papayiannis et al., (2011) found that 49 plant species were TYLCV hosts belonging to 15 families, namely, Amaranthaceae, Chenopodiaceae, Compositae, Convolvulaceae, Cruciferae, Euphorbiaceae, Geraniaceae, Leguminosae, Malvaceae, Orobanchaceae, Plantaginaceae, Primulaceae, Solanaceae, Umbelliferae and Urticaceae.

Symptoms:  The disease is easily identified when tomato are infected at seedling stage.

Young leaves and shoots are severely stunted resulting in bushy and upright seedling growth.  Leaves exhibit the most diagnostic symptoms of small leaves, upward and inward rolling of the margins, interveinal and marginal yellowing, distinct stunting and often a bushy appearance.  Flowers either do not develop or fall off.  When plants are infected early, they lose vigor and fruit production is reduced or stopped. When infected at a later stage of development, fruit already formed continue to develop more or less normally however, additional fruit are not produced.

Leaf curl symptom is not limited to tomato but also produced in TYLCV-infected varieties of common bean and lisianthus (Eustoma grandiflorum).

Most wild tomato species include members that are either immune or symptomless carriers of the virus. Certain weeds are also asymptomatic (Malva parviflora). It is not known how well whiteflies acquire virus from symptomless hosts (Gilbertson, 2008). Plants used to rear whiteflies are immune to the virus (CABI, 2014).

Damage Potential:  TYLCV is one of the most damaging pathogens of tomato and losses up to 100% in commercial fruit production in fields are not uncommon (UCIPM, 2008).  Yield loss results in fewer numbers of fruit produced.  Fruit present at time of infection remain on the plant but few will set more or less normally.  It has been shown experimentally that the younger the plants are at the time of infection, the more severe is the reduction in fruit yield.  Experimentally, compared to non-inoculated plants, 3-10 week old TYLCV inoculated tomato plants showed 63% reduction in number of fruit, while 15 week old plants did not show significant yield reduction (CABI, 2014).  In the USA, mostly minor losses of less than 10% were noted in 1997-2000 due to aggressive actions taken by tomato growers.

Severe losses in commercial bean production in Israel and southern Spain have been reported (Navot et al., 1992; Navas-Castillo et al., 1999).

Disease Cycle and Transmission: TYLCV is transmitted by the whitefly vector, Bemisia tabaci in a persistent manner.  The vector acquires the virus (acquisition access period) after feeding on an infected plant for 15-30 minutes, then there is a latent period of 18-24 hours within the insect after which the virus can be inoculated into a healthy plant during a feeding period of at least 15 minutes (inoculation access period) by the insect. A single white fly can inoculate more than one plant.  TYLCV is retained within the vector when the latter molts and is detected in every developmental stage of the vector.  It does not multiply within the vector and is not passed on from generation to generation through the eggs of the vector, although research results may be controversial:  Ghanim et al. (1998) detected TYLCV in whitefly eggs that suggested transovarial passage (CABI, 2014; VIDE, 1996).  Whiteflies remain viruliferous for approximately two weeks.  Large populations of B. tabaci moving between crops can cause rapid spread and high levels of disease.

The pathogen is spread over short distance by the white fly vector.  TYLCV is also transmitted by grafting and poorly by mechanical inoculation, but it is not transmitted by contact between plants.  Seed transmission has not been reported.  Over long distances, TYLCV is spread mainly through the movement of infected plants.  As symptoms can take up to 3 weeks to develop, symptomless infected plants can often go unnoticed.  Hitch-hiking, virus-carrying whiteflies can also accompany tomato and other host plants moved over long distances as well as strong winds and storms.

Worldwide Distribution:   TYLCV has been reported from several countries in Asia, Africa, North America (Mexico and USA), Central America and Caribbean, South America (Venezuela only), Europe, and Oceania (CABI, 2014, EPPO, 2014).

In the USA, TYLCV is present in Alabama, Arizona, California, Florida, Georgia, Hawaii, Kentucky, Louisiana, Mississippi, North Carolina, South Carolina, and Texas.

Official Control:  TYLCV is included on the Harmful Organism Lists of 49 countries in Asia, Europe, and South America, including Antigua and Barbuda Islands (PCIT, 2014). As a result of the estimated losses caused by TYLCV in 1999-2003, several countries in Australia and The European Union have established strict quarantine measures against the whitefly vector (CABI, 2014).

California Distribution: Imperial and Riverside Counties.

Major tomato-producing regions of California, including the Sacramento and San Joaquin valleys, do not promote the establishment of TYLCV.  According to Gilbertson (2008), the vector is not found in those regions for two main reasons.  First, the vector is intolerant of the region’s cool winter temperatures.  Second, the Central Valley has a natural tomato-free period from late November to early February during which period the amount of virus inoculum is significantly reduced until tomatoes are planted in late winter to early spring.  So, even if TYLCV is able to overwinter during the tomato-free period, it would take a long time for viral inoculum to build up to damaging levels in the field.  The virus is able to infect other host plants however, it builds up quickly on tomato.

There have not been any establishments of any Bemisia tabaci haplotype overwintering populations north of Fresno County due to the cooler winter temperatures and lack of the right amount of degree days for development (personal communication: Dr. Raymond Gill, CDFA Entomologist, 2013).  Nevertheless, it is not unusual for the whitefly vector species to be introduced into and possibly establish within contained controlled environments of nursery greenhouses in northern California regions (CDFA Pest Detection Records and personal communication: Dr. Gillian Watson, CDFA Entomologist).

California Interceptions:  There are no records of TYLCV detected in incoming plant shipments to California.

The risk Tomato yellow leaf curl virus would pose to California is evaluated below.

Consequences of Introduction: 

1)  Climate/Host Interaction: Evaluate if the pest would have suitable hosts and climate to establish in California. Score:

– 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.

Risk is Medium (2) – The establishment of TYLCV within CA is closely related to the establishment of its whitefly vector, Bemisia tabaci. The virus (and the vector) is already established in commercial and urban environments in Imperial and Riverside Counties.  However, the vector is limited to the southern regions of the state as it is intolerant of the cooler winter temperatures present in the main tomato-growing regions in northern California.  Also, the vector is unable to build up to damaging levels because of the tomato-free production period present in the Central Valley.   

2)  Known Pest Host Range: Evaluate the host range of the pest:

– Low (1) has a very limited host range
– Medium (2) has a moderate host range
– High (3) has a wide host range.

Risk is Medium (2) – While tomato is the main host for TYLCV, minor hosts include moderate numbers of cultivated plants, ornamentals, and weeds belonging to several plant species and families.

3)  Pest Dispersal Potential: Evaluate the dispersal potential of the pest:

– 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.

Risk is High (3) – The spread of TYLCV is through artificial means. Short distance spread is mainly through its white fly vector, Bemisia tabaci, whereas long distance spread is mainly through movement of TYLCV-infected plants and strong winds that may move the vector over longer distances than it own capability.

4)  Economic Impact: Evaluate the economic impact of the pest to California using these criteria:

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.

– 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.

Risk is High (3) – TYLCV is one of the most economically damaging pathogens of tomato.  Incidence and spread of the virus could gravely affect the tomato industry in particular, by lowering crop yield, value, increasing production costs, affecting local and international  markets, negatively change normal cultivation practices to prevent incidence of further occurrence and spread of the virus and its whitefly vector.

5)  Environmental Impact: Evaluate the environmental impact of the pest on California using these criteria:

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.

Score the pest for Environmental Impact:

– 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.

Risk is Medium (2) – Several weeds and wild tomato varieties are considered hosts of TYLCV, however, wild tomato and several weed hosts are asymptomatic and it is not known how well the whitefly vector will acquire the virus from such infected hosts that may comprise natural environments.  The effect on these hosts is not known.  Nevertheless, TYLCV infections may impact home/urban gardening and cultivation of ornamentals.

Consequences of Introduction to California for Tomato yellow leaf curl virus

Add up the total score and include it here. (Score)

Low = 5-8 points
Medium = 9-12 points
High = 13-15 points

Total points obtained on evaluation of consequences of introduction of TYLCV to California = (12).

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. (Score)

-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.

Evaluation is Low (-1). 

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:

Up-to-date field data is always needed on the probable establishment and spread of TYLCV beyond the known regions in Imperial and Riverside counties.  Such information would be obtained through periodic surveys of tomato fields.  Also not known is the distribution of the virus in natural environments and the potential that infected natural hosts may play in its possible spread to tomato fields.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Tomato yellow leaf curl virus is B.

References:

CABI   2014.  Tomato yellow leaf curl virus full datasheet.  Crop Protection Compendium.  http://www.cabi.org/cpc/datasheet/1695

EPPO, 2014.  Tomato yellow leaf curl virus (TYLCV0).  New PQR database.  Paris, France:  European and Mediterranean Plant Protection Organization.  http://newpqr.eppo.int

Fauquet C. M, D. P.Maxwell, B. Gronenborn, and J. Stanley.  2000.  Revised proposal for naming geminiviruses. Archives of Virology, 145(8):1743-1761; 11 ref.

Ghanim, M., S. Morin, M. Zeidan and H. Czosnek, 1998. Evidence for transovarial transmission of tomato yellow leaf curl virus by its vector, the whitefly Bemisia tabaci. Virology (New York), 240(2):295-303.

Gilbertson, R. L.  2008.  Tomato Yellow Leaf Curl.  UC IPM Pest Management Guidelines: Tomato.  UC ANR Publication 3470.  http://www.ipm.ucdavis.edu/PMG/r783103311.html

Nakhla, M. K and D. P. Maxwell 1998. Epidemiology and management of tomato yellow leaf curl disease. In: Hadidi A, Khetarpal RK, Koganezawa H, eds. Plant Virus Disease Control. St Paul, USA: APS Press, 565-583.

Navas-Castillo, J. S., Sanchez-Campos and J. A. Diaz.  1999. Tomato yellow leaf curl virus causes a novel disease of common bean and severe epidemics in tomato in Spain. Plant Disease, 83:29-32.

Navot, N, M., Zeidan, E. Pichersky, D. Zamir and H. Czosnek.  1992. Use of the polymerase chain reaction to amplify tomato yellow leaf curl virus DNA from infected plants and viruliferous whiteflies. Phytopathology, 82(10):1199-1202.

Papayiannis, L. C., N. I. Katis, A. M. Idris and J. K. Brown.  2011. Identification of weed hosts of Tomato yellow leaf curl virus in Cyprus. Plant Disease, 95(2):120-125. http://apsjournals.apsnet.org/loi/pdis .

PCIT.  2014.  USDA Phytosanitary Certificate Issuance & Tracking System.  https://pcit.aphis.usda.gov/PExD/faces/ReportHarmOrgs.jsp .

Rojas, M. R., T. Kon, E. T. Natwick, J. E. Polston, F. Akad, and R. L. Gilbertson.  2007.  First report of Tomato yellow leaf curl virus associated with Tomato Yellow Leaf Curl Disease in California.  Plant Disease, 91:1056.

VIDE.  2014.  Tomato yellow leaf curl bigeminivirus.  Plant Viruses Online: Description and Lists from the VIDE Database.  http://pvo.bio-mirror.cn/descr840.htm

Responsible Party:

Dr. 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 niederhauserii Abad & J. Abad, 2014

California Pest Rating for
Phytophthora niederhauserii Abad & J. Abad, 2014
Pest Rating: B
PEST RATING PROFILE
Initiating Event:  

None.  A permanent rating for Phytophthora niederhauserii is proposed herein.

History & Status:

Background: In 2003, Abad and Abad reported the discovery of a Phytophthora species associated with necrotic collars, stems and roots of arborvitae (Thuja occidentalis L.) and English ivy (Hedera helix L.) grown in greenhouses in North Carolina.  They named the species, P. niederhauseria and submitted the ITS (Internal transcribed spacer) genetic sequences on GenBank-NCBI before publishing an official description of the species.  Soon other researchers from around the globe found that they were working with the same species based on the similarity of their test ITS sequences with that of P. niederhauseria in GenBank.  The species was discovered in 13 countries and associated with ornamentals, fruit trees and native plants.  However, it was only recently, that an official description of the species was published and the name, P. niederhauserii was validated (Abad et al., 2014).

Hosts: Abad et al., (2014) isolated P. niederhauserii from 33 plant hosts in 25 families from various countries.  A number of shrubs and herbaceous ornamental plants are hosts of the pathogen.  Few agricultural crops are also included.  Thuja occidentals (arborvitae), Hedera helix (English ivy), Abies nordmanniana, Acacia dealbata (Mimosa), Banksia baxteri, Banksia prionotes (acorn banksia), Banksia speciosa, various Begonia hybrids,  Callistemon citrinus, Ceanothus sp., Chamaecyparis lawsoniana, Cistus monspeliensis, C. salviifolius (sageleaf rockrose),  Grevillea olivacea, Heuchera sp. Iris sp. Juniperus sp., Kalanchoe blossfeldiana (kalanchoe), Manihot esculenta, Metrosideros villosa, Peperomia clusiifolia,Pistacia lentiscus, Plumbago sp., Prunus dulcis (almond), Punica granatum, Rhododendron catawbiense (catawba rhododendron), Sinningia speciosa (gloxinia), Spathiphyllum sp., Vitis vinifera (grape), and Xanthorrhoea australis (Farr & Rossman, 2014; Abad et al., 2014).

Symptoms:  Generally, Phytophthora niederhauserii infestations cause symptoms of root and stem collar necrosis resulting in wilting and leaf desiccation or drop in host plants.  In Norway, symptoms of P. niederhauserii infestation on greenhouse-potted begonia, gloxinia and ivy included necrotic roots and stems with necrosis extending to the leaves via the petioles.  Wilting of the entire plant was observed in gloxinia and ivy. In kalanchoe, only root discoloration and stunted plant growth are apparent (Herrero et al., 2008).  In Spain, symptoms on almonds included leaf chlorosis and drop, wilting, cankers and gum exudation.  In spring, symptoms included failure to leaf-out, death of scion and rootstock sprouts (Pérez-Sierra et al., 2010). The pathogen caused collar and root necrosis in boxwood associated with severe wilting and desiccation of foliage (Józsa et al., 2010).

Damage Potential: Quantitative economic losses in plant production due to Phytophthora niederhauserii have not been reported, however, infestations may result in significant damage and loss in production and stands of host plants by causing root and crown/basal stem rots of infected plants. Nursery ornamentals and plants grown in natural ecosystems are particularly affected. Infections may lead to death of the plant.  Generally, annual plants and young seedlings of trees may be killed by the disease within a few days, weeks or months (Agrios, 2005). The pathogen can potentially cause crown rot in grapes – as detected in South Africa and in almonds in Turkey (Abad et al., 2014).       

Disease Cycle: Generally, species of Phytophthora that cause root and stem rots survive cold winters or hot and dry summers as thick-walled, resting spores (oospores and chlamydospores) or mycelium in infected roots, stems or soil.  During spring, the oospores and chlamydospores germinate to produce motile spores (zoospores) that swim around in soil water and roots of susceptible hosts. The pathogen infects the host at the soil line causing water soaking and darkening of the trunk bark. This infected area enlarges and may encircle the entire stem of small plants which wilt and eventually die.  On large plants and trees, the infected, necrotic area may be on one side of the stem and become a depressed canker below the level of the healthy bark.  Collar rot canker may spread down the root system. Roots are invaded at the crown area or at ground level.   Mycelium and zoospores grow in abundance in cool, wet weather causing damage where the soil is too wet for normal growth of susceptible plants and low temperatures (15-23°C) prevail (Agrios, 2005).

Transmission:  Infected soils, plants, nursery and planting stock, seedlings, run-off and splash irrigation water, cultivation equipment and tools that may spread contaminated soil and plant materials to non-infected sites.

Worldwide Distribution:  Widespread.  Thirteen countries, namely, Australia, Hungary, Israel, Italy, Japan, the Netherlands, Norway, South Africa, Spain, Taiwan, Turkey, the United Kingdom and the USA (Abad et al., 2014).

In the USA, Phytophthora niederhauserii has been found in California, North Carolina, South Carolina (Robayo-Camacho et al., 2009; Farr & Rossman, 2014).

Official Control:  None reported.

California Distribution: Phytophthora niederhauserii has been detected in Santa Barbara County and counties within the San Joaquin Valley namely, Kings, Fresno, Kern, Merced, Stanislaus, Madera, San Luis Obispo and Tulare counties (CDFA Plant Pathology Database, 2007; Schmidt et al., 2012).

California Interceptions:  The pathogen has not been intercepted in quarantine shipments of plants.

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

Consequences of Introduction: 

1)  Climate/Host Interaction: Evaluate if the pest would have suitable hosts and climate to establish in California. Score:

– 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

Risk is High (3) – Phytophthora niederhauserii has already been detected in few nurseries in California and has been reported (Schmidt et al., 2012) as an aggressive pathogen of almonds in the San Joaquin Valley of California.  Within California, it is likely to establish in cool, wet climates in susceptible hosts.

2)  Known Pest Host Range: Evaluate the host range of the pest:

– Low (1) has a very limited host range
– Medium (2) has a moderate host range
– High (3) has a wide host range

Risk is Medium (2) –Currently at least 33 plant species in 25 families have been reported as hosts of the pathogen.  A number of shrubs and herbaceous ornamental plants are included. Few agricultural crops (almonds and grapes) are also included.  The latter are grown as major crops in California.

3)  Pest Dispersal Potential: Evaluate the dispersal potential of the pest:

– 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

Risk is High (3) – Phytophthora niederhauserii is primarily spread artificially via infested soils, plants, nursery and planting stock, seedlings, run-off and splash irrigation water, cultivation equipment and tools that may spread contaminated soil and plant materials to non-infected sites.

4)  Economic Impact: Evaluate the economic impact of the pest to California using these criteria:

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.

– 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

Risk is High (3) – The pathogen could lower crop yield, increase production costs and cause loss of market of infected nursery stock and agricultural crops. The capability of the pathogen to survive and spread in infected soils and irrigation water could require changes in normal cultivation practices of host plants.

5)  Environmental Impact: Evaluate the environmental impact of the pest on California using these criteria:

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.

Score the pest for Environmental Impact:

– 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

Risk is High (3) – A number of plants in natural ecological habitats are hosts to the pathogen.  Subsequently, natural plant communities, ecosystems, threatened or endangered species as well as home/urban gardening and ornamentals may be negatively impacted.

Consequences of Introduction to California for Phytophthora niederhauserii:

Add up the total score and include it here. (Score)

Low = 5-8 points
Medium = 9-12 points
High = 13-15 points

Total points obtained on evaluation of consequences of introduction of Phytophthora niederhauserii to California = (14).

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. (Score)

-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.

Evaluation is High (-3). In California, Phytophthora niederhauserii has been detected in Santa Barbara County and the San Joaquin Valley counties.

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:

Statewide surveys specifically for Phytophthora niederhauserii have not been conducted to include all nursery sites and natural ecosystems (e.g., restoration sites) as well as almond and grapevine cultivation sites.  Subsequent data generated may result in the addition of new host plant species and further distribution of the pathogen within California.  All this may alter the current proposed rating of P. niederhauserii.

Conclusion and Rating Justification:

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

References:

Abad Z. G, and J. A. Abad.  2003.  Advances in the integration of morphological and molecular characterization in the genus Phytophthora: the case of P. niederhauseria sp.nov. Phytopathology 408 93:S1.

Abad, Z. G., J. A. Abad, S. O. Cacciola, A. Pane, R. Faedda, E. Moralejo, A. Pérez-Sierra, P. Abad-Campos, L. A. Alvarez-Bernaola, J. Bakonyi, A. Józsa, M. L. Herrero, T. I. Burgess, J. H. Cunnington, I. A. Smith, Y. Balci, C. Blomquist, B. Henricot, G. Denton, C. Spies, A. Mcleod, L. Belbahri, D. Cooke, K. Kageyama, S. Uematsu, I. Kurbetli and K. Keğirmenci.  2014.  Phytophthora niederhauserii sp. nov., a polyphagous species associated with ornamentals, fruit trees and native plants in 13 countries.  Mycologia, 106 (3): 431-447.

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

Farr, D.F., & Rossman, A.Y.  2014.  Fungal Databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved November 10, 2014, from http://nt.ars-grin.gov/fungaldatabases/

Jo´zsa A, J. Bakonyi, L. Belbahri, ZA Nagy, A. Szigethy, G. Boha´r and S.Woodward. 2010. A new species of Phytophthora reported to cause root and collar rot of common boxwood, Nordmann fir and Port Orford cedar in Hungary. Plant Pathology 59:1166–1167.

Pe´rez-Sierra A, A. Leo´n, LA A´ lvarez, S.Alaniz, M. Berbegal, J. Garcı´a- Jime´nez, P. Abad-Campos. 2010. Outbreak of a new Phytophthora sp. associated to severe decline of almond trees in eastern Spain. Plant Disease 94:534–541.

Robayo-Camacho E, Hwang J, Jeffers SN.  2009.  A diversity of species of Phytophthora found on floriculture crops.  Phytopathology 99:S109, doi:10.1094/PHYTO-99-1-0109

Schmidt, L. S., R. G. Bhat, D. A. Kluepfel and G. T. Browne.  2012.  Resistance to Phytophthora in new rootstocks for almond and stone fruits.  Phytopathology, 102:S4.106.

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

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