Category Archives: Fungi

Fungi, Plant Pathogens

Didymella bryoniae (Auersw.) Rehm [teleomorph] (Auersw.) Rehm

California Pest Rating for
Didymella bryoniae (Auersw.) Rehm [teleomorph] (Auersw.) Rehm
Pest Rating:  B
PEST RATING PROFILE
Initiating Event:

None.  The risk of infestation of Didymella bryoniae in California is evaluated and a permanent rating is herein proposed. 

History & Status:

Background:  Didymella bryoniae is the fungal pathogen that causes gummy stem blight of cucurbits disease affecting members of the family Cucurbitaceae.  Gummy stem blight was first reported in 1891 in France, Italy and the United States and affects the leaves, stems, fruits and seeds of all cucurbits.   The disease is most common in subtropical and tropical regions globally but also found in temperate regions, especially on winter squash and pumpkin and greenhouse grown cucumber (Sitterly & Keinath, 1996).  The disease is most common in the southern United States, and in California, gummy stem blight was first reported in greenhouse-produced transplants of watermelon in the Salinas Valley (Koike, 1997).  Since 1997, there have not been any further reports of the pathogen in California.

Didymella bryoniae is the sexual (teleomorph) stage of the fungus that produces ascospores, while Phoma cucurbitacearum represents the asexual stage (anamorph) that produces conidia.  Didymella bryoniae was originally described as Sphaeria bryoniae, but since then has undergone several classifications that resulted in synonymizations of many different species.

Hosts: Members of the family Cucurbitaceae including wax gourd (Benincasa hispida), watermelon (Citrullus lanatus), melon (Cucumis melo), cucumber (C. sativus), pumpkin (Cucurbita sp.), giant pumpkin (C. maxima), ornamental gourd (C. pepo), buffalo gourd (C. foetidissima), bottle gourd (Lagenaria siceraria), bitter gourd (Momordica charantia), loofah (Luffa cylindrica), white bryony (Bryonia alba), red bryony (B. dioica), chayote (Sechium edule), and burcucumber (Sicyos angulatus) Occasionally, the pathogen has been found in members of Solanaceae, Caricaceae, and Primulaceae (CABI, 2015; Farr & Rossman, 2015).

Symptoms:  Didymella bryoniae invades the leaves and stems of watermelon, cucumber, and muskmelon (cantaloupe) and gummy stem blight diseased plants may exhibit a variety of symptoms which are referred to as leaf spot, stem canker, vine wilt and black fruit rot (Ferreira & Boley, 1992).  Initial spots on leaves, petioles and stems usually become pale brown or gray. On stems, spots usually start at the joints, frequently elongate into streaks and exude an amber-colored gummy liquid.  Lesions on leaves and fruit initiate as spreading water-soaked areas which in leaves may have a chorotic halo, become light brown and irregular in outline, and necrotic.  Leaves wilt and collapse; affected plants wilt and eventually die. On fruit, faded and irregular spots first form on the surface and eventually turn dark and may have a hardened droplet of exudates in the center; cracked sunken lesions form with internal rotting – especially in storage fruit.  In certain kinds of squash, lesions are superficial and spread almost over the entire fruit surface.  When seed-transmitted, the pathogen causes damping-off thereby, killing seedlings.  In the field, initial symptoms include plant collapse with sunken girdling cankers that result in total loss of plants.  Vine cankers are common near the crown of the plant.  (Agrios, 2005; CABI, 2015; Ferreira & Boley, 1992; Koike, 1997; Sitterly & Keinath, 1996.)

The main diagnostic symptoms are the gummy exudates on stem and fruit lesions, and the presence of abundant closely spaced groups of pale-colored pycnidia (asexual fruiting body) and dark brown to black-colored perithecia (sexual fruiting body) on fruit, stem or leaves.  During rainy seasons lesions can become water-soaked and spread resulting in severe defoliation.  Gummy substances may exude from cracks, and severe infections can result in death of plants (CABI, 2015).

Damage Potential: Didymella bryoniae has the potential of damaging plant growth causing reductions in plant growth, death of infected plants, fruit rot, and seedling death resulting in significant crop losses.

Disease Cycle:   The pathogen usually overwinters in diseased plant debris as chlamydospores and possibly in or on seeds.  Subsequently, spores or infected seed result in primary infection of plants. Cucurbit plants are predisposed to infection by wounds and bruises although uninjured plants have also been shown to become infected when exogenous nutrients are present (Ferreira & Boley, 1992).  The disease thrives in cool moist climates with an optimum temperature of 20-28 C for development.  Moisture, especially extended periods of wetness, is necessary for infection (at least 1 hour) and disease development.  Leaves are penetrated directly through the cuticle or through intercellular spaces around the bases of trichomes. Stems are penetrated through wounds and fruit are penetrated through wounds or flower scars at the time of pollination.  Fruit rot initiates approximately 3 days following infection.  Following penetration and development, the fungus produces numerous pycnidia and perithecia.  Pycnidia are filled with conidia (spores) that protrude from the fruiting body in a gelatinous substance appearing as long cream to pink tendrils.  Water dissolves this gelatinous substance and the conidia are dispersed usually by wind and rain.  Perithecia are also produced along with pycnidia and filled with ascospores. Both types of spores serve as inoculum for infection.  Neither type survives long after dispersal (Agrios, 2005; Ferreira & Boley, 1992; Sitterly & Keinath, 1996).

Transmission:  Infected planting material (transplants), infected fruit, plant debris, weeds, and soil.  In addition, conidia can be transmitted by air transport and water splashing (Ferreira & Boley, 1992).  Seed transmission has only been demonstrated experimentally (Brown et al., 1970; CABI, 2015; Lee et al., 1984).  Reports of seed transmission are conflicting and there is no evidence that seed transmission occurs naturally although fruiting bodies (pycnidia and perithecia) of the pathogen have been found on naturally infected cucumber and pumpkin seeds (CABI, 2015).  The striped cucumber beetles (Diabrotica undecimpunctata howardii and Acalymma vittatum) are believed to transmit D. bryoniae in a nonpersistent manner by providing wounds in plants as avenues for fungal infections. It has also been shown experimentally that cucumber plants infested with melon aphids were susceptible to D. bryoniae and powdery mildew (Ferreira & Boley, 1992).

Worldwide Distribution:  Didymella bryoniae is distributed worldwide in several countries in Asia, Africa, North America, Central America and Caribbean, South America, Europe, and Oceania (CABI, 2015).

In the USA, it has been reported from Florida, Georgia, New York, North Carolina, and South Carolina.

Official Control:  Didymella bryoniae is included on the ‘Harmful Organism Lists’ for nine countries namely: Bangladesh, Ecuador, Egypt, Indonesia, Iran, Israel, Panama, Syrian Arab Republic and Timor-Leste (PCIT, 20115).  It is a quarantine pest in Jordan (EPPO, 2015).   Currently, it is an actionable, temporary ‘Q’-rated pathogen in California.

California Distribution: Didymella bryoniae has only been reported once in 1997 in Salinas in greenhouse watermelon transplants.  The diseased plants would have been destroyed following detection.  The pathogen has not been reported since then and is not known to be established in California.

California Interceptions:  None reported.

The risk Didymella bryoniae 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) – Didymella bryoniae requires cool and moist conditions to infect cucurbit hosts and cause gummy stem blight disease.  At least 1 hour of wetness is required for infection and extended periods for disease development.  This may limit the establishment of the disease in cucurbit productions in California and may also be why this disease has not been observed outside greenhouse production in California since the early 1990s.  Therefore, a ‘medium’ rating is given to this category.

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 Medium (2) – The host range is mainly limited to various species of the Cucurbitaceae family.  Nevertheless, Cucurbitaceous hosts, including watermelon, melon, squash and cucumber, are widely grown commercially within 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) – Under favorable environmental conditions Didymella bryoniae has a high reproductive rate and depends on wind and moisture or rain for its short distance dispersal.  Infected planting material, infected fruit, plant residues, weeds, soil, and possibly seed provide the means for long distance dispersal, also in fields and greenhouses. In addition, the striped cucumber beetles are believed to transmit D. bryoniae in a nonpersistent manner by providing wounds in plants as avenues for fungal infections.  

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) –  The cucurbit gummy stem blight pathogen could lower crop value and yield, cause increases in production costs for disease management, and negatively change normal cultural practices to mitigate potential damages.  There is also the possibility for the pathogen to be vectored by pestiferous striped cucumber beetles.  Therefore, a ‘high’ rating is given to this category.   

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) – Cucurbitaceous plants grown in home/urban gardens could be negatively impacted if infected with Didymella bryoniae.

Consequences of Introduction to California for Didymella bryoniae:

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 Didymella bryoniae to California = Medium (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 in California (0). 

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 (Medium).

Uncertainty:

Infested seeds and transplants are a ready source of introduction of the pathogen to CA fields.  The future status of Didymella bryoniae, gummy stem blight of cucurbits disease, can be known through periodic surveys, diligent monitoring and testing of seed/plants in greenhouses and will be necessary in order to mitigate risk of field introduction and potential establishment of the pathogen in California soils.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for the anthracnose pathogen, Didymella bryoniae is B.  

References:

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

Brown, M. E., E. M. Howard, and B. C. Knight. 1970. Seedborne Mycosphaerella melonis on cucumber. Plant Pathology, 19:198.

CABI.  2015.  Didymella bryoniae (gummy stem blight of cucurbits) datasheet (full) report.  Crop Protection Compendium.  www.cabi.org/cpc/

EPPO.  2015.  Stagonosporopsis cucurbitacearum (DIDYBR).  European and Mediterranean Plant Protection Organization PQR database.  http://www.eppo.int/DATABASES/pqr/pqr.htm .

Farr, D. F., and A. Y. Rossman.  2015.  Fungal Databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved July 14, 2015, from http://nt.ars-grin.gov/fungaldatabases/

Ferreira, S. A., and R. A. Boley.  1992.  Didymella bryoniae Gummy stem blight, black rot, canker (Plant Disease Pathogen).  http://www.extento.hawaii.edu/kbase/crop/Type/d_bryon.htm

Koike, S. T.  1997.  First report of gummy stem blight, caused by Didymella bryoniae, on watermelon transplants in California.  Plant Disease, 81:1331. http://dx.doi.org/10.1094/PDIS.1997.81.11.1331B.

Lee, D. H., S. B. Mathur, and P. Neergaard. 1984. Detection and location of seed-borne inoculum of Didymella bryoniae and its transmission in seedlings of cucumber and pumpkin. Phytopathologische Zeitschrift, 109(4):301-308.

PCIT.  2015.  USDA Phytosanitary Certificate Issuance & Tracking System. July 21, 2015.  https://pcit.aphis.usda.gov/PExD/faces/ReportHarmOrgs.jsp .

Sitterly, W. R., and A. P. Keinath.  Gummy stem blight.  1996.  In, Compendium of cucurbit diseases.  Compendium of cucurbit diseases ed. T. A. Zitter, D. L. Hopkins, and C. E.  Thomas, APS Press  pg 27-28. http://www.apsnet.org/publications/apsnetfeatures/Pages/GummyStemBlight.aspx .

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 spaethianum (Allesch.) Damm, P. F. Cannon & Crous, 2009

California Pest Rating for
Colletotrichum spaethianum (Allesch.) Damm, P. F. Cannon & Crous, 2009
Pest Rating:  B
PEST RATING PROFILE
Initiating Event:  

On March 27, 2015, a mail shipment containing Iris sp. plants with leaf spots was intercepted by the CDFA Dog Team, at the United States Postal Service Center in West Sacramento, Yolo County.   The plants had been shipped by a private owner in Gowen, Oklahoma.  Samples collected were submitted to the CDFA Plant Pathology Laboratory and the fungal pathogen, Colletotrichum spaethianum, was isolated from the diseased plants and identified by Suzanne Latham, CDFA plant pathologist.  The species identity was confirmed on August 18, 2015, by the USDA PPQ National Mycology Laboratory.  This detection was considered a new US record and reportable by the USDA. Consequently, the shipment of Iris sp. plants was destroyed.  The risk of infestation of C. spaethianum in California is evaluated and a permanent rating is proposed.     

History & Status:

Background:  The fungal pathogen Colletotrichum spaethianum was originally described in 1895 under the name Vermicularia spaethiana from dead stems of Funkia univittata (synonym Hosta sieboldiana) in Berlin, Germany.  A living strain of the original material of pathogen is no longer available however, as a result of taxonomic and phylogenetic studies, Damm et al., (2009) combined V. spaethiana to the genus Colletotrichum becoming C. spaethianum and designated an epitype (representative specimen in place of the non-available original specimen) from the same host in the same city as the original fungal species.

Hosts: Hosta sieboldiana, Hemerocallis sp.(daylily), H. flava, H. fulva, H. citrine, Hymenocallis americana (northern spider lily), Lilium sp. (Lily), Peucedanum praeruptorum (Qian Hu), Allium fistulosum (Welsh onion), (Damm et al., 2009, 2012; Yang et al., 2009; Yang et al., 2014; Guo et al., 2013; Vieria et al., 2014; Farr & Rossman, 2015). The CDFA detection of Colletotrichum spaethianum in Iris sp. is a new host record.

Symptoms:  Colletotrichum spaethianum infected host plants exhibit symptoms of anthracnose which include reddish brown to dark brown leaf and stem necrotic spots and wilting of leaves which often result in dieback and reduction in plant quality.

Damage Potential:  Anthracnose disease caused by Colletotrichum spaethianum 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 spaethianum 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:  Europe: Germany; Asia:  South Korea; North America: Florida, South America: Oceania: New Zealand (Cai, et al., 2009; Damm et al., 2009; Farr & Rossman, 2015; Yang, et al., 2009; Yang et al., 2014).

Official Control:  In California C. spaethianum is an actionable, Q-rated pathogen, and infected plant material is subject to destruction or rejection.   The species is considered ‘reportable’ by the USDA.

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

California Interceptions:  There has been one interception of Colletotrichum spaethianum –infected (Iris) plants that originated in Oklahoma (see ‘Initiating event’).

The risk Colletotrichum spaethianum 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. spaethianum requires humid, wet, rainy weather for conidia to infect host plants. This environmental requirement may limit the ability of the pathogen to establish and spread in less conducive climates. Also confining is the limited host range comprising primarily of lily and iris ornamental plants which are cultivated in nurseries, residential and commercial community environments such as parks and gardens.  The pathogen could establish within these limited regions when grown under favorable moist conditions.

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 spaethianum is limited to hosta, daylilies, northern spider lily, lily, iris, Qian Hu (Chinese medicinal plant), and Welsh 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) – In particular, nursery and private productions of lily, hosta, and iris ornamental plants can be limited by their susceptibility to anthracnose under wet conditions. Therefore, under suitable climates, the pathogen could lower plant growth, 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 High (3) – The pathogen could significantly impact cultural practices or home/urban garden plantings. Also, the pathogen could impact endangered lily plants in California, namely: western lily (Lilium occidentale) and Pitkin Marsh lily (Lilium pardalinum ssp. Pitkinense) (State and federally listed endangered, threatened and rare plants of California, California Natural Diversity Database, California Department of Fish and Wildlife, July 2015).

Consequences of Introduction to California for Colletotrichum spaethianum:

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 spaethianum 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 not established (0).  Colletotrichum spaethianum is not established in California.  The intercepted C. spaethianum-infected iris plants were either rejected or destroyed. 

Final Score:

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

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

Uncertainty:

None.

Conclusion and Rating Justification:

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

References:

Cai, L., Hyde, K.D., Taylor, P.W.J., Weir, B.S., Waller, J.M., Abang, M.M., Zhang, J.Z., Yang, Y.L., Phoulivong, S., Liu, Z.Y., Prihastuti, H., Shivas, R.G., McKenzie, E.H.C., and Johnston, P.R. 2009. A polyphasic approach for studying Colletotrichum. Fungal Diversity 39: 183-204.

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/

Guo, M., Y. M. Pan, Y. L. Dai, and Z. M. Gao.  2013.  First report of leaf spot caused by Colletotrichum spaethianum on Peucedanum praeruptorum in China.  Plant Disease, 97:1380.

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.

Santana, K. F. A., C. B. Garcia, K. S. Matos, R. E. Hanada, N. R. Sousa, G. F. and Da Silva.  2015. First report of anthracnose caused by Colletotrichum spaethianum on Allium fistulosum in Brazil.  Plant Disease (Accepted for publication) posted on line on 3Aug 2015, First Look.  http://dx.doi.org/10.1094/PDIS-07-15-0737-PDN.

Vieira, W. A. S., S. J. Michereff, A. C. Oliveira, A. Santos and M. P. S. Câmara.  2014.  First report of anthracnose caused by Colletotrichum spaethianum on Hemerocallis flava in Brazil.  Plant Disease, 98:997.  http://dx.doi.org/10.1094/PDIS-10-13-1026-PDN

Yang, Y. L., Z. Y. Liu, L. Cai, K. D. Hyde, Z. N. Yu and E. H. C. McKenzie. 2009. Colletotrichum anthracnose of Amaryllidaceae. Fungal Diversity 39: 123-146

Yang, H. C., J. S. Haudenshield and G. L. Hartman. 2014. Colletotrichum incanum sp. nov., a curved-conidial species causing soybean anthracnose in USA. Mycologia 106: 32-42.

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

Melampsoridium hiratsukanum S. Ito ex Hirats. f., (Alder Rust)

California Pest Rating
Melampsoridium hiratsukanum S. Ito ex Hirats. f.,
(Alder Rust)
Pest Rating:  C
PEST RATING PROFILE
Initiating Event:

The pest rating of Alder Rust has been raised by certain counties and related nurseries due to its increased spread within California.  Currently, Melampsoridium hiratsukanum has a temporary Q rating that is herein reconsidered for a permanent rating.

History & Status:

Background:  Three Melampsoridium species are reported as causing foliar rust on alder (Alnus spp.) namely, M. alni, M. betulinum and M. hiratsukanum. Confusion has existed on the distinct identity of the species as all three are morphologically similar.  This confusion has caused doubt about the authenticity of many older records.  However, since the late 1990s, the use of DNA analysis has confirmed the identities of the three species. Melampsoridium hiratsukanum belongs to the family Pucciniastraceae in the order Pucciniales.  The species was first described on Manchurian alder (A.hirsuta) from Hokkaido in Japan in 1927.

Disease cycle:  Melampsoridium hiratsukanum is a heteroecious rust that produces two different fruiting bodies (uredinia and telia) on the leaves of its main host alder (Alnus spp.) and two different fruiting bodies (spermagonia and aecia) on its alternate host larch (Larix sp.).  On alder, the fungal species forms uredinia which give rise to urediniospores.  These spores are produced repeatedly and form the major stage for reproduction and dispersal.  Urediniospores are the only spores that re-infect their same host plant repeatedly.  Later, the pathogen produces the sexual, overwintering fruiting body structure or telia which give rise to thick-walled teliospores.  During the following spring, teliospores germinate forming a basidium which produces haploid basidiospores.  Basidiospores may infect young needles of larch (Larix spp.) and develop to form spermogonia – which form pycniospores or spermatia and receptive hyphae.  Following fertilization of spermatia and compatible receptive hyphae, dikaryotic mycelium is produced which forms aecia that produce aeciospores. Aeciospores may infect alder but not other larch or Larix spp. On infection, aeciospores produce more dikaryotic mycelium that this time forms uredinia that produce urediniospores thereby completing the life cycle.

The fungal pathogen may also exhibit a shortcut life cycle especially where the alternate aecial host (Larix spp.) is not present.  In such situations, the life cycle of the pathogen is completed on alder alone without the need of the alternate host and is therefore, reproduces and spreads only through the production of urediniospores.  Such may be the situation with the occurrence of the disease on alder plants in California nurseries.  The pathogen has not been reported on an alternate host in California.  It is likely that the urediniospores re-infect fresh alder leaves thereby enabling their survival and perpetuating the disease through a rapid build-up of inoculum.  Such a shortcut life cycle is known for many rust fungi with alternate hosts and is assumed to occur in Austria and Hungary (NOBANIS, 2007; Szabo, 2002).

Dispersal and spread:  Alder may be infected by aeciospores, or as discussed above for California, it may be infected with urediniospores produced in other alder plants.  Also, it may survive as mycelium infecting buds or with urediniospores.  The rust fungus spreads from plant to plant mainly by windblown spores.  Urediniospores are formed repeatedly and in abundance and may be transmitted over several hundred kilometers by strong winds and then washed down by rain on to host plants that are readily infected.  Aeciospores are also capable of long distance dispersal.  Over the past 10 years, the introduction and rapid spread of the pathogen in Europe was most likely due mainly to dry airborne spores, although specific distances have not been reported (Lane et al., 2013).  Infected nursery stock or plantings also provide a means for long distance spread of the pathogen which is capable of surviving in bud scales in dormant buds.

Hosts:  Alder (Alnus spp.), Black, European or common alder (Alnus glutinosa), Manchurian alder (A. hirsuta), Grey or Speckled alder (A. incana), Red alder (A. rubra) (EPPO, 2014), white alder (A. rhombifolia) (Blomquist et al., 2014); Larch (Larix spp.), Dahurian larch (L. gmelinii), Siberian larch (L. russica) (EPPO, 2014) and White or Downy birch (Betula pubescens) (Lane et al., 2013).  Experimental hosts: European larch (L. decidua), Tamarack or American larch (L. laricina) (Lane et al., 2013).

Symptoms and damage potential:  Infected white alder leaves exhibit numerous small orange-yellow uredinia pustules on the lower leaf surfaces, with corresponding yellow to orange spots on the upper surface.  Later, leaves turn dark brown and curl inwards with the production of telia.  Infected leaves often turn yellow, die and sometimes drop prematurely. The disease causes considerable damage to alder foliage in late summer causing them to be easily distinguished from a distance.  Repeated infections can cause defoliation and crown thinning leading to tree death (Lane et al., 2013).

Worldwide Distribution: Records of the detection of M. hiratsukanum prior to 2005 may be dubious due to taxonomic difficulty that existed in distinguishing it from other closely related species, viz. M. alni and M. betulinum without using molecular analysis.  Many records prior to 2005 may have been of M. betulinum (Lane et al., 2013).  Nevertheless, it is probable that M. hiratsukanum originated in Eastern Asia and has spread to temperate regions of Europe and North America.  Reliable records of the global distribution of M. hiratsukanum (EPPO, 2014) include:

Asia: China, Japan, Nepal (Adhikari & Manandha, 1989; EPPO, 2014)

Europe: Austria, Czech Republic, Estonia, Finland, France, Germany, Hungary, Italy, Latvia, Lithuania, Norway, Poland, Romani, Russia, Slovakia, Switzerland, Turkey, Ukraine, UK.

North America: Canada, USA (California and Oregon:  Bloomquist et al., 2014; Pscheidt & Ocamb, 2013).  Most likely, it is widespread in nurseries of western US coastal states (Blomquist 2014: pers. comm.)

Official Control: Currently, there are no reports of official control imposed against Melampsoridium hiratsukanum.

California Distribution:  Melampsoridium hiratsukanum is most likely widespread on alders in California nurseries (Blomquist 2014: pers. comm.). The pathogen has been in California since 1931 and a first published report was issued in 2014 of its detection in white alder from a nursery in Santa Cruz County (Blomquist et al., 2014).  However, disease symptoms on trees caused by the pathogen have not been found in California wild lands – mainly due to the absence to high moisture conditions necessary for the perpetuation of the disease in its natural habitat.

California Interceptions:  The pathogen has been in California since in the 1931 as evident by a sample that was submitted to the Federal Herbarium in Beltsville, MD.  However, this sample had been misidentified, and later, when it was correctly identified the revised identification was never published.  The pathogen has also been found in several locations in California Central Valley.

The risk Alder Rust 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):  Melampsoridium hiratsukanum is already established and suspected to be widely distributed wherever alder is grown in California nurseries.  The pathogen has not been found in California wild lands.

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): The host range is mainly limited to alder and larch trees. Only a few records of its occurrence on birch are from Europe (U.K.).  In California, the pathogen has only been found on alder.     

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): Alder Rust has high reproduction and dispersal potential via windblown spores that are capable of being transmitted by strong winds over distances of several hundred kilometers.  Also they may be spread over long distances via infected 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): Trees infected with Melampsoridium hiratsukanum could cause significant loss of foliage, thereby generally reducing their yield and value in nursery 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 Medium (2): Alder rust has been in California since 1931, although the pathogen was misidentified.  Although it is difficult to find nursery alder trees that are not infected with the pathogen, according to Dr. Cheryl Blomquist (CDFA, pers. comm.), this rust pathogen has not been found in the wild lands, and no significant impact to California’s environment has been reported.  Nevertheless, it may cause significant concern for home/urban gardens or ornamental settings.

Consequences of Introduction to California for Alder Rust:

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 (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 (-2).  Melampsoridium hiratsukanum is widespread in California nurseries, but has not been detected in wild lands.

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:

 While Melampsoridium hiratsukanum has been in California since 1931, it was not possible to distinguish it from M. alni and M. betulinum based on morphology alone.  The latter two species have been reported earlier from California.   It may well be those earlier detections are, in fact, M. hiratsukanum which have yet to be molecularly differentiated.  If this is determined to be so, then it will only strengthen the proposed C rating for this pathogen, as also will its detection in California’s wild land habitats.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Alder Rust is C.

References:

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

Blomquist, C. L., H. J. Scheck, J. Haynes, P. W. Woods and J. Bischoff.  2014.  First published report of rust on white alder caused by Melampsoridium hiratsukanum in the United States.

EPPO.   2014.  Melampsoridium hiratsukanum (MELDHI).  PQR database.  Paris, France: European and Mediterranean Plant Protection Organization.  http://www.newpqr.eppo.int.

Lane, C., S. Matthews Berry and H. Anderson.  2013.  Rapid pest risk analysis for Melamsoridium hiratsukanum.  The Food & Environment Research Agency, Version 3, March, 2013.

NOBANIS.  2007.  Melampsoridium hiratsukanum.  NOBANIS – Invasive Alien Species Fact Sheet.  http://www.nobanis.org/files/factsheets/Melampsoridium_hiratsukanum.pdf.

Pscheidt, J. W. and C. M. Ocamb.  2013.  Pacific Northwest Plant Disease Management Handbook.  URL: pnwhandbooks.org/plantdisease/node/2616.

Szabo, I.  2002.  First report of Melampsoridium hiratsukanum on common alder in Hungary.  Plant Pathology, 51:804.

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

Sarocladium oryzae (Sawada) W. Gams & D. Hawksworth

California Pest Rating for
Sarocladium oryzae (Sawada) W. Gams & D. Hawksworth
Pest Rating: A
PEST RATING PROFILE
Initiating Event:

In August 2014, during a routine Controlled Import Permit inspection, Anthony Jackson, USDA APHIS PPQ WR, sampled rice seedlings imported from Spain and grown under post quarantine permit conditions in a greenhouse in Pleasant Grove, Sutter County, California.  A fungal pathogen, Sarocladium oryzae was detected in the sampled seedlings and identified by Cheryl Blomquist, plant pathologist, CDFA.  This identification marked the first detection of S. oryzae in California.  Later, in October 2014, the same pathogen was again detected by Suzanne Latham, plant pathologist, CDFA, in rice seedlings grown in the same Pleasant Grove greenhouse.  Subsequently, all post quarantine rice seedlings held at the greenhouse were destroyed by steam sterilization at the CDFA Plant Pathology Laboratory.   The fungal pathogen was assigned a Q (temporary) rating which is reassessed herein for the proposal of a permanent rating.

History & Status:

Background:  Sarocladium oryzae is a fungal pathogen that causes the sheath rot of rice disease.  Historically, the pathogen was initially described as Acrocylindrium oryzae by Sawada in 1922 from Taiwan.  In 1956, a species which caused symptoms similar to Sarocladium oryzae, was named by Gams and Hawksworth as S. attenuatum.  However, genetic and biochemical analyses revealed no differences between S. oryzae and S. attenuatum and subsequently the latter species was declared a synonym of S. oryzae (Bridge et al., 1989).  Sarocladium oryzae belongs to the order Hypocreales in the class Sordariomycetes, Phylum Ascomycota.

Hosts: Oryza sativa (rice) is the main host. However, rice cultivars differ in their susceptibility to the pathogen.  Other naturally infected hosts include O. rufipogon (wild rice) and grasses: Hymanchne assamica, Leersia hexandra, Panicum walense.  Other hosts include monocot weeds found in rice fields which may serve as a natural source of inoculum for infection of rice: Cyperus iria (rice flat sedge), C. tenneriffae, C. difformis (small-flowered nut sedge), Echinochloa crus-galli (barnyard grass), Eleusine indica (goose grass) and Monochoria vaginalis.  Also, Echinochloa colona (jungle rice).  Other monocot agricultural crops include millets, sorghum and maize. Several weeds and wild rices are included experimental, greenhouse-tested hosts (CABI, 2014; EPPO, 2014).

Symptoms:  The pathogen mainly attacks the uppermost leaf sheaths which enclose young panicles at the booting stage.  Lesions develop, initiating as irregular spots 5-10 mm, which become dark lesions, sometimes oblong, with brown margins and light-brown centers or grayish-brown throughout. Lesions may coalesce and cover most of the leaf sheath.  Young lesions bear whitish, powdery fungal growth on the outer and inner sides of affected sheaths, while old lesions have less or no fungal growth and appear as dry, brownish lesions with the enclosed rotted panicle. When infected early, young panicles remain compressed within the sheath, do not develop and rot, or only partially emerge from the sheath.  Outside the rotted sheath, partially emerged spikelets/grains are dark brown, chaffy and partially filled.

Infected seeds are usually symptomless and germinate normally.  Sometimes, primary and secondary leaves wither prematurely due to S. oryzae infection (CABI, 2014).

Damage Potential:  In India, rice yield losses of 10-26% and 50% are reported (Chakravarty and Biswas, 1978; CABI, 2014).  In Taiwan, 3-20% incidence of sheath rot disease have been observed reaching 85% in susceptible varieties.  Losses include production of fewer spikelets per panicle, lower grain weight of diseased panicles, and increased grain chaffiness. In India, 70% disease severity with 15-35% grain chaffiness, and 100% seed sterility in severe cases has been reported (CABI, 2014).

Disease Cycle: Sarocladium oryzae survives as mycelium on and in seeds.  Fungal inoculum or spores (conidia) from several infected weed hosts are capable of infecting rice.  The pathogen invades rice through the stomata and wounds and grows intercellularly within vascular and mesophyll tissues.  Additionally, wounds created in rice plants facilitate infection and disease development.  This is particularly true of wounds caused by mites, stem borers, mealy bugs, and rice bug.  The incidence and severity of sheath rots of rice disease is favored at 20-30°C and 65-85% relative humidity.

Transmission:  Seed – the pathogen is externally and internally seedborne.  Sachan and Agarwal (1995) found S. oryzae within the seedcoat, endosperm and embryo of discolored seeds however the pathogen may also be detected on seeds that are not discolored. S. oryzae may also be spread through infected straw and plant parts – leaves, seeds, flowers, inflorescences, cones, and calyx.

Worldwide Distribution:  Africa:  Burundi, Cameroon, Cote d’Ivore, Gambia, Kenya, Madagascar, Niger, Nigeria, Senegal, Tanzania; North America: Mexico, USA; Central America: Cuba; South America: Argentina, Brazil, Colombia, Venezuela; Asia:  Bangladesh, Brunei Darussalam, China, India, Indonesia, Iran, Japan, Malaysia, Nepal, Pakistan, Philippines, Saudi Arabia, Sri Lanka, Taiwan, Tajikistan, Thailand, Uzbekistan, Vietnam, Oceania: Australia.  In the USA it is reported as being widespread, and specifically present in Louisiana (CABI, 2014; EPPO, 2014).

Official Control: Sarocladium oryzae is on the “Harmful Organism List’ for Honduras and Peru (PCIT, 2014). The species is currently listed as a Q rated pest for California.

California Distribution: Sarocladium oryzae is not present in California.

California Interceptions:  Prior to its current detection in Sutter County (see ‘Initiating event’) Sarocladium oryzae has not been detected in incoming plant shipments to California.

The risk Sarocladium oryzae 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) – If allowed to enter California, Sarocladium oryzae is capable of establishing a widespread distribution in the States rice cultivated acreage.

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 Medium (2) – Rice is the major host of the pathogen and is grown in significant acreage in California.  Other hosts include several weeds that are capable to harboring inoculum for rice infections.

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) – Long distance spread is mainly through infested seed.  Infected plant parts and rice straw also serve as significant means of spread.  Potentially, conidia may be moved over short distances via winds, and wind-blown water droplets.  

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) – The pathogen could significantly impact rice production in California by lowering crop yield and value which would result in the loss of markets.  Additionally, certain species of mites and stem borers have been reported to harbor large numbers of fungal spores (conidia) and spread the pathogen to non-infected plants thereby, increasing the incidence of the sheath rot of rice disease.

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) – Several species of natural grasses and wild rice are hosts of Sarocladium oryzae. If these hosts are infected they may significantly impact the ecosystem of a natural environment. 

Consequences of Introduction to California for Sarocladium oryzae:

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 Sarocladium oryzae 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 not established (0).

Final Score:

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

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

Uncertainty:

Sarocladium oryzae has not been previously detected in California.  The initial detection recorded in this report was made in a greenhouse and subsequently all rice plants within the greenhouse were destroyed.  No targeted surveys of natural environments, rice fields or seed rice storage facilities have been conducted for the detection of this pathogen within California.  If detected, the proposed rating may alter.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for the sheath rot of rice pathogen, Sarocladium oryzae is A.

References:

CABI.  2014.  Sarocladium oryzae full datasheet report.  Crop Protection Compendium.  www.cabi.org/cpc/.

Chakravarty, D. K, and S. I. Biswas. 1978. Estimate of yield loss in rice affected by sheath rot. Plant Disease Reporter, 62:226-227.

EPPO.  2014.  Sarocladium oryzae (SARMOR).  European and Mediterranean Plant Protection Organization PQR database.  http://www.eppo.int/DATABASES/pqr/pqr.htm.

Farr, D.F., & Rossman, A.Y. Fungal Databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved December 4, 2014, from http://nt.ars-grin.gov/fungaldatabases/.

Groth, D.  1992.  Sheath rot.  In, Compendium of Rice Diseases edited by R. K. Webster and P. S. Gunnell.  The American Phytopahtological Society, Minnesota, USA: 25.

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

Sachan, I. P., and V. K. Agarwal. 1995. Seed discolouration of rice: location of inoculum and influence on nutritional value. Indian Phytopathology, 48(1):14-20; 17 ref.

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: A

Posted by ls

Fungi, Plant Pathogens

Peronospora belbahrii (Downy mildew of basil)

California Pest Rating for
Peronospora belbahrii
(Downy mildew of basil)
Pest Rating: C
PEST RATING PROFILE
Initiating Event:

During June 2014, Cheryl Blomquist, CDFA Plant Pathologist, detected Peronospora belbahrii in basil plants grown in a Nursery in Alameda County.  The plants had been purchased from a different nursery in Sebastopol, Sonoma County.  In 2008, the pathogen had been detected in basil plants produced in various nurseries.  Trace-back investigation of the 2008 detections revealed that the seeds had originated in Italy.  Presently, the origin of seeds cultivated in Sonoma County is not known.  Peronospora belbahrii currently has a Q rating that is herein reassessed for the proposal of a permanent rating.

History & Status:

Background:  Peronospora belbahrii is a fungal pathogen that causes downy mildew disease of basil (Ocimum spp. of the family Lamiaceae).  Traditionally it was believed that the downy mildew disease of Lamiaceae, including the downy mildew of basil, was caused by a single species namely, P. lamii.  However, that view has been proven inaccurate by several researchers, and Belbahri et al. (2005) showed through ITS sequencing that a then newly occurring fungal species on basil was different from P. lamii.  Later, Thines et al. (2009) formally introduced this fungal species as P. belbahrii and distinguished it from a different closely related species that parasitizes sage (Salvia).  They determined that P. belbahrii isolates infected both basil and coleus (Solenostemon sp.), and while those isolates seemed closely related, Thines et al. (2009) refrained from distinguishing them as two separate species until further studies have been conducted (albeit depending on the taxonomical concept taken, downy mildew on basil and coleus may be attributed to one or two different species).  Downy mildew of basil was first reported from Africa from where it is assumed to have originated on sweet basil (Ocimum basilicum). Later, it was reported from Europe.  It continued to spread globally and is considered a relatively new disease of basil in the United States.

Disease cycle:  Peronospora belbahrii 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, currently only one mating type of P. belbahrii has been found in the USA.  Consequently, no oospores are formed and the pathogen is unable to survive harsh cold winters (Grabowski, 2014).  It is likely that the pathogen survives as mycelium and/or condia (spores) in infected plant buds, plant debris, leaf tissue and shoots.  Peronospora belbahrii thrives in warm, humid climates.  However, it can tolerate cool weather, infect and produce conidia at temperatures as low as 59°F (Grabowski, 2012).  Generally, 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 is seed borne and can also be spread through contaminated plant cuttings, transplants, and fresh leaves.  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:  Ocimum spp. (basil, including culinary and ornamental varieties), Solenostemon sp. coleus (Thines et al., 2009), Agastache sp. hyssop (Henricot et al., 2009).

Symptoms and damage potential: Infection starts on lower leaves and progresses upwards.  Initially symptoms appear as yellowing (slightly chlorotic) of affected leaves with the veins remaining green. Following this, the central portion of a chlorotic lesion may become necrotic; slight curvature of leaves occurs followed by premature leaf fall.  In some cases entire area of the leaf surface is affected.  Grey to brown, furry or downy (conidia) growth is apparent on underside of symptomatic leaves giving the leaves a dirty appearance.  These symptoms may sometimes occur on upper surfaces of leaves.

Under cool dry conditions infected transplants and leaves may not exhibit symptoms (Grabowski, 2012).   Basil plants not showing symptoms at harvest are capable of developing symptoms during transport (Roberts et al., 2009).  Chen et al. (2010) noted that in Taiwan, the pathogen caused chlorosis and leaf shrinkage on basil in the field, but did not cause any symptom on coleus.

Downy mildew is one of the most destructive diseases of sweet basil which is grown as a specialty crop in greenhouses and production fields in several regions of the United States and other countries. Once infected, basil plants are no longer marketable.  Under favorable weather conditions complete yield loss can be expected.  In Florida, almost 100% incidence of the disease occurred causing complete yield loss in the field for fresh and potted herbs markets (Roberts et al., 2009).  The frequency of disease occurrence and the percentage of infected leaf area were 80-90% and 17-20% respectively on full-grown basil leaves grown a greenhouse in Hungary (Nagy & Horvath, 2011).

Worldwide Distribution: Basil downy mildew has been reported from several countries and continents including, Argentina (greenhouse), Belgium, Benin, Cameroon, Canada, Cuba, Cyprus, France, Switzerland, Hungary, Israel, Iran, Italy, New Zealand, South Africa, Taiwan, Tanzania, Uganda, United Kingdom (Zhang et al., 2012; CABI, 2014; EPPO, 2014; Henricot et al., 2009).

In the United States, the pathogen was first discovered in Florida in 2007 (Roberts et al., 2009).  Since then, the disease has been found throughout the eastern United Sates and commercial basil production regions in the Midwest and California, namely, Alabama, California, Connecticut, Delaware, Georgia, Hawaiian Islands, Illinois, Indiana, Kansas, Kentucky, Massachusetts, Missouri, Minnesota, New Jersey, New York, North Carolina, Ohio, Oregon, Pennsylvania, South Carolina, Texas, Vermont, Virginia and Wisconsin (Zhang et al., 2012; Grabowski, 2012; PNW, 2014).

Official Control: Currently, the pathogen is not officially controlled in the United States Department of Agriculture.

California Distribution:  In California, the pathogen has been found in nursery and/or field environments of Alameda, San Diego, San Joaquin, Ventura, and Southern Valley Counties.

California Interceptions:  Recently P. belbahrii was detected in basil plants grown in a nursery in Alameda County.  The plants had originated from a different nursery in Sonoma County (see ‘Initiating Event’).

The risk Downy mildew of basil 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): As evident from current distribution records in California, Peronospora belbahrii – causing downy mildew of basil – is able to develop in warm (not hot), humid weather conditions and can tolerate cool climates as well.  Interestingly, in San Diego County, basil was drip irrigated and grown in a hot inland valley.  Under those conditions the disease still spread, possibly due to the humid microenvironment that developed in a basil field where plants were grown close together so that dew was produced when evening temperatures dropped.

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): The host range is limited to basil, coleus and hyssop.  Although several species and varieties of basil exist, the host range is thus far limited to three plant genera.

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 seed borne as well as 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): Presence of the pathogen in field and/or greenhouse environments can significantly lower crop value and yield.  Infected, symptomatic 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): Home/urban gardening of basil and cultivation of coleus and hyssop ornamental plants can be significantly impacted if the pathogen is present in private home garden environments.  

Consequences of Introduction to California for Downy mildew of basil:

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 High (-3):  To date, the pathogen has been detected in more than four non contiguous 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:  

Surveys for the detection of P. belbahrii have not been conducted to fully establish its presence in field environments within California.  Results of future survey may result in further detections of the pathogen in new locations.  This will only strengthen the current proposed C rating.  However, due to the devastating effects on crop production, direct action is necessary to mitigate risk of establishment and spread of P. belbahrii on host plants particularly grown in nursery environments.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Downy mildew of basil is C.

References:

Belbahri, L., G. Calmin, J. Pawlowski and F. Lefort.  2005.  Phylogenetic analysis and real time PCR detection of a presumbably undescribed Peronospora species on sweet basil and sage.  Mycological Research, 109:1276-1287.

Blomquist, C.L., S. Rooney-Latham and P. A. Nolan.  2009. First report of downy mildew on field-grown sweet basil caused by a Peronospora sp. in San Diego County, California. Plant Disease 93:968.

CABI.  2014.  Pernospora belbahrii data sheet report (basic).  Crop Protection Compendium.  http://www.cabi.org/cpc/datasheetreport?dsid=118352.

Chen, C. H., J. H. Huang, J. H. and T. F. Hsieh.  2010.  First report of Peronospora belbahrii causing downy mildew on basil.  Plant Pathology Bulletin, 17:177-180.

EPPO.  2014.  Peronospora belbahrii (PEROBE).  PQR database.  Paris, France: European and Mediterranean Plant Protection Organization.  http://www.newpqr.eppo.int.

Grabowski, M.  2012.  Basil Downy Mildew Peronospora belbahrii.  Regents of the University of Minnesota.  University of Minnesota Extension. http://www.extension.umn.edu/garden/yard-garden/vegetables/basil-downy-mildew/docs/basil-downy-mildew-pub.pdf.

Henricot, B., J. Denton, J. Scarce, A. V. Barnes and C. R. Lane.  2009.  Peronospora belbahrii causing downy mildew disease on Agastache in the UK: a new host and location for the pathogen.  New Disease Reports, 20:26.

Nagy, G. and A. Horvath.  2011.  Occurrence of downy mildew caused by Peronospora belbahrii on sweet basil in Hungary.  Plant Disease, 95:1034.1.

PNW.  2014.  Basil, Sweet (Ocimum basilicum) – Downy Mildew.  Pacific Northwest Plant Disease Management Handbook.  http://pnwhandbooks.org/plantdisease/basil-sweet-ocimum-basilicum-downy-mildew.

Roberts, P. D., R. N. Raid, P. F. Harmon, S. A. Jordan and A. J. Palmateer.  2009.  First report of Downy Mildew caused by a Peronospora sp. on basil in Florida and the United States.  Plant Disease 93: 199.

Thines, M., S. Telle, S. Ploch and F. Runge.  2009.  Identity of the downy mildew pathogens of basil, coleus and sage with implications for quarantine measures.  Mycological Research 113:532-540.

Wyenandt, C. A., J. E. Simon, M. T. McGrath and D. L. Ward.  2010.  Susceptibility of basil cultivars and breeding lines to downy mildew (Peronospora belbahrii).  2010.  HortScience 45:1416-1419.

Zhang, S. Z. Mersha, P. D. Roberts and R. Raid.  2012.  University of Florida, IFAS Extension Document PP271.  http://edis.ifas.ufl.edu/pdffiles/PP/PP27100.pdf.

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

Puccinia crepidis-japonicae (Lindr.) Dietel (Rust)

California Pest Rating for
Puccinia crepidis-japonicae (Lindr.) Dietel
(Rust)
Pest Rating: D 
PEST RATING PROFILE
Initiating Event:

Recently, the USDA NPAG (New Pest Advisory Group) reported and evaluated the detection of Puccinia crepidis-japonicae in Gainesville, Florida, thereby, marking the first record of this pathogen in the USA.  Subsequently, the risk and consequences of its introduction to, and establishment in California is assessed here and a permanent rating is proposed.

History & Status:

Background:  In February 2015, the fungal rust pathogen, Puccinia crepidis-japonicae, was discovered on the exotic weed Youngia japonica (oriental false Hawksbeard) in Florida (USDA NPAG, 2015).  The pathogen primarily attacks weed plants.  While P. crepidis-japonicae is reported to attack plant genus Prenanthes, the host Y. japonica was originally described under the genus name Prenanthes japonica. Therefore, it is likely that the pathogen may be limited to the host belonging to Youngia spp.  This common host, Youngia spp., is present in southern California, and Y. japonica grows there as a garden weed at the edge of lawns and planting beds.

Puccinia crepidis-japonicae has not been reported from California. However, there is a very early record of a different species belonging to the same group, namely, P. crepidis-acuminatae P. Syd. & Syd., which was detected on naked-stem Hawksbeard, (Crepis runcinata which is now a synonym of Youngia runcinata) and tapertip Hawksbeard (Crepis acuminata, synonym of Y. acuminata) in California (Blasdale, W. C. 1919: A preliminary list of the Uredinales of California. University of California Publications in Botany, 7:101-157).

Puccinia crepidis-japonicae is not considered an economically damaging pathogen as it is associated with non-economically important plants. Pereira et al., 2002 suggested that P. crepidis-japonicae may play a significant role as a biocontrol agent against its weed host.  In Florida, the possibility of using this exotic rust against the exotic host, Youngia japonica, is being considered (USDA NPAG, 2015).  However, it is not known if the pathogen kills its host since it needs the latter in order to live as a parasite.

Disease cycle:  The complete life cycle and climate requirements for disease development for Puccinia crepidis-japonicae are not known.  In general, rust pathogens require living host plants to complete a life cycle.  The life cycle may be completed in one or two hosts – and this is not known for P. crepidis-japonicae. Rusts attack only certain genera or varieties of plants.  This appears to be the case for P. crepidis-japonicae. Rusts may have a short cycle (microcyclic) producing only two different spores: teliospores and basidiospores, or a long cycle (macrocyclic) producing five different spores: teliospores, basidiospores, spermatia, aeciospores, and urediniospores. Only urediniospores and teliospores are reported for P. crepidis-japonicae, so this pathogen may be macrocyclic. Urediniospores infect host plants and can rapidly spread to cause new and multiple infections of host plants (Agrios, 2005).

Dispersal and spread:  The pathogen is spread from plant to plant mainly by windblown spores.  Urediniospores can be transported over several hundred kilometers by strong winds and washed down by rain to available hosts.  Insects, animals, humans, and rain may also aid in spreading spores to non-infected plants. Infected nursery plants also aid in introducing and spreading the pathogen.

Hosts: Asteraceae – Prenanthes sp. (rattlesnake root), Youngia fusca, Y. japonica (oriental false Hawksbeard), Y. tenuifolia, Y. japonica (originally cited as Crepis japonica which is now a synonym of Y. japonica) (Farr & Rossman, 2015).

Symptoms and damage potential:  Puccinia crepidis-japonicae primarily attacks weed plants (e.g., Youngia japonica) producing dark brown, irregularly oval-shaped leaf lesions containing urediniospores (Pereira et al., 2002).

Worldwide Distribution: Asia: China, Korea, Japan, Yoron Islands; North America: United States; Oceania: Australia, New Caledonia; South America: Brazil (Farr & Rossman, 2015; USDA NPAG, 2015; Pereira, et al., 2002; Zhuang, 1989).

In the United States, it has only been reported from Florida (USDA NPAG, 2015).

Official Control: Puccinia crepidis-japonicae is not listed as a harmful organism by any country (PCIT, 2015).  No official control of this pathogen is reported.

California Distribution: Puccinia crepidis-japonicae is not present in California.

California Interceptions:  None reported.

The risk Puccinia crepidis-japonicae Rust 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 Low (1):  If introduced, Puccinia crepidis-japonicae is likely to establish under favorable environmental conditions in limited areas within southern California where its common host, Youngia spp. is present.

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): The host range is limited to weed plants in the genus Youngia spp. in the family Asteraceae. 

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): Puccinia crepidis-japonicae has both high reproduction and dispersal potential through the production of abundant, infective urediniospores and the ease of their spread by winds, insects, animals, humans, and rain to non-infected host plants.  

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 Low (1): Puccinia crepidis-japonicae is not considered an economically damaging pathogen as it is associated with non-economically important plants or weeds.

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 Low (1): None.

Consequences of Introduction to California for Puccinia crepidis-japonicae Rust:

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 = 7

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).

Final Score:

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

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

Uncertainty:

Details of the life cycle and complete host range are unknown.  However, it is unlikely this knowledge will significantly alter the proposed rating for Puccinia crepidis-japonicae.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Puccinia crepidis-japonicae Rust is D.

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 August 31, 2015, from http://nt.ars-grin.gov/fungaldatabases/

Pereira, O. L., J. R. P. Cavallazzi and R. W. Barreto.  2002.  First report of Uredo crepidis-japonicae and Septoria crepidis on Crepis japonica in Brazil. Fitopathológicas Brasileira 27 (3):319.

USDA NPAG.  2015.  NPAG report Puccinia crepidis-japonicae (Lindr.) Dietel: Rust.  USDA/APHIS/ PPQ/CPHST/PERAL NPAG Report 20150615.docx. 6 pg.

Zhuang, J. Y. 1989. Rust fungi from the desert of northern Xinjiang. Acta Mycologica Sinica 8(4):259-269.

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: D

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

Fungi, Plant Pathogens

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

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

During July, 2014, mango fruit exhibiting spots or lesions were intercepted by the CDFA Dog Team in Santa Clara County and samples of symptomatic fruit were sent to the CDFA Plant Pathology Laboratory for diagnosis.  The associated anthracnose fungal pathogen, Colletotrichum asianum, was identified by Suzanne Latham, CDFA plant pathologist and later confirmed by USDA.  Subsequently, the fruit was destroyed and the shipment was traced back by the USDA to Florida and C. asianum was detected in fruit still on the tree.  This detection marked the first report of the pathogen in the USA (USDA, 2015).  Since its first detection and during April and June 2015, C. asianum continued to be detected in mango fruit shipments destined for Alameda, Butte, Los Angeles, Merced, Riverside, Sacramento, San Joaquin, and Santa Clara Counties.  The shipments were intercepted at USPS distribution facilities by Dog Teams.   On July 7, 2015, C. asianum was found to be associated with necrotic spots in mango leaves of plants in a nursery in Imperial County.  This was the first detection of the pathogen from leaves. In all cases of interceptions mentioned afore, subsequent to the detection of C. asianum, all fruit and plant shipments were received from Florida and either destroyed or rejected from entering California.  Currently, C. asianum 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 asianum was first reported to be associated with coffee berries (Coffea arabica) in northern Thailand (Prihastuti et al., 2009).  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 with DNA sequences (Prihastuti et al., 2009; Weir et al, 2012).

Hosts: Mangifera indica (mango) and Coffea arabica (coffee) (Prihastuti et al., 2009; Weir et al., 21012).

Symptoms:  Initially, small, dark brown circular spots are produced on mango fruit and leaves infected with Colletotrichum asianum.  These spots increase rapidly in size and coalesce to form dark depressed anthracnose lesions in ripened fruit (Krishnapillai & Wilson Wijeratnam, 2014). 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 asianum 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 asianum 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:  Africa: South Africa; Asia: Japan, Sri Lanka, Thailand, Philippines; South America: Brazil, Colombia, Panama; Australia; North America: Florida (Farr & Rossman, 2015; Krishnapillai & Wilson Wijeratnam, 2014; Lima et al., 2013; Prihastuti et al., 2009; Sharma et al., 2013; USDA, 2015; Vieira et al., 2014; Weir et al., 2012).

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

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

California Interceptions:  During 2015, Colletotrichum asianum has been intercepted several times mainly in shipments of mango fruit and less frequently in mango plants (leaves) that originated in Florida (see ‘Initiating event’).

The risk Colletotrichum asianum 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. asianum 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. Also limiting is the very narrow host range of C. asianum comprising mango and coffee.  Coffee is not cultivated in California and mango has limited production in the foothills of southern California or warm locations in the Coachella Valley.  It is also grown in residential backyards and few nurseries, either as fruit or nursery stock.  The pathogen could establish within these limited regions under conducive climates.

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) – The host range of Colletotrichum asianum is limited to mango and coffee.

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) – Mango fruit production, in particular, can be limited by its 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 asianum:

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 karstii 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 not established (0).  Colletotrichum asianum is not established in California.  All instances of interception of C. asianum-infected mango fruit and plants were either rejected or destroyed. 

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:

Periodic surveys need to be conducted to confirm the presence/absence of C. asianum 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 asianum is B.

References:

CABI.  2015.  Colletotrichum asianum 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 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.

Krishnapillai, N., and R. S. Wilson Wijeratnam.  2014.  First report of Colletotrichum asianum causing anthracnose on Willard mangoes in Sri Lanka.  New Disease Reports, 29:1. http://dx.doi.org/10.5197/j.2044-0588.2014.029.001 .

Lima, N. B., M. V. de A. Batista, MAde Morais Júnior, M. A. G. Barbosa, S. J. Michereff, K. D. Hyde, M. P. S. Câmara.  2013. Five Colletotrichum species are responsible for mango anthracnose in northeastern Brazil. Fungal Diversity, 61:75-88. http://rd.springer.com/article/10.1007/s13225-013-0237-6.

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., M. Gryzenhout, K. D. Hyde, A. K. Pinnaka, and B. D. Shenoy.  2015.  First report of Colletotrichum asianum causing mango anthracnose in South Africa.  Plant Disease, 99:725.  http://dx.doi.org/10.1094/PDIS-08-13-0837-PDN .

USDA. 2015.  Email from John H. Bower, USDA ,APHIS, PPQ, PHP to Nick Condos, CDFA, subject: Colletotrichum asianum on mango from CA and from the source tree in FL (first records for Continental US), dated April 30, 2015 6:26 am.

Vieira, W. A. S., S. J. Michereff, M. A. de Morais Jr., K. D. Hyde, and M. P. S. Câmara.  2014.  Endophytic species of Colletotrichum associated with mango in northeastern Brazil.  Fungal 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

Myrtle Rust: Puccinia psidii G. Winter

California Pest Rating for
Puccinia psidii G. Winter
(Myrtle Rust)
Pest Rating: C
PEST RATING PROFILE
Initiating Event:

A review of the current pest rating of Myrtle Rust has been requested by certain counties due to the increased detection of the pathogen within California.  Currently, Puccinia psidii has a B rating.

History & Status:

Background:  In 1884, Winter first described the fungal rust pathogen, Puccinia psidii from infected guava (Psidium guajava), of the plant family Myrtaceae, in Brazil.  Since then, several rust species described from infected members of Myrtaceae and named after the host they were detected on, are now considered synonyms of P. psidii. This pathogen is also commonly known as guava rust, eucalyptus rust (in Florida, the Caribbean, and Central and South America), and ohi’a rust (in Hawaii) after its respective host.  In 2010, P. psidii was detected in Australia (as Uredo rangelii) on common myrtle and subsequently known as myrtle rust – a name which best fits P. psidii as it “captures the occurrence of the pathogen on a very wide host range including numerous genera and species of Myrtales” (Roux et al., 2013).

There are several biological biotypes or races of Puccinia psidii known to exhibit varying virulence on different hosts, environmental tolerances, sporulation characteristics, and spore survival (Glen et al., 2007).

Puccinia psidii is native to South and Central America, but since its original report, it has spread to several countries worldwide, including California, Florida and Hawaii in the USA.  As a result of its spread, the pathogen is considered an important quarantine threat to many countries (Glen et al., 2007). Puccinia psidii was first reported in the USA in Florida in 1977, then in Hawaii in 2005 and in California in 2006.  It is likely that the pathogen was present in California prior to 2006 and introduced from Florida through imported, diseased plants (Killgore & Heu, 2007; Marlatt & Kimbrough, 1979; Mellano, 2006).  In 2011, the rust pathogen was first reported on Melaleuca quinquenervia (paperbark) in a nursery in San Diego, California (Zambino & Nolan, 2011) but has now spread to outside environments and landscape (personal communications: Pat Nolan, plant pathologist, Department of Agriculture, Weights and Measures, County of San Diego, CA.) Although the pathogen currently has a B rating that allows implementation of eradicative action in nurseries, this may not have always been implemented, thereby, providing a pathway of introduction and spread to outside environments.  Furthermore, this rust – as well as many other rust pathogens – is very difficult to eradicate due to its ease of long distance dispersal and wide host range.  Once established in a region it can and has spread rapidly to amenity plantings, commercial and native environments (CABI, 2015).

Disease cycle:  Puccinia psidii is considered to complete its life cycle on the same host (autoecious), having an incomplete lifecycle. The suggestion that the pathogen is heteroecious with an unknown aecial host is considered doubtful (Glen et al., 2007).     With the exception of spermagonia, all other spore states are produced on the same host.  Urediniospores are produced abundantly under natural conditions, but the production of teliospores and basidiospores are comparatively rare and spermagonia and aeciospores are unknown.    Under favorable conditions of humidity and temperature, urediniospores present on host germinate to penetrate the tissue through stomata.  As the fungus grows, uredinia (fruiting structures) are formed and urediniospores are produced in abundance.   Disease development is favored by low temperatures of about 20°C, high relative humidity (80%) at night and high levels of airborne urediniospores.  On rose apple (Syzygium jambos) in Brazil, rust epidemics incidence and severity were dependent on the duration of leaf wetness over 90% or leaf wetness periods greater than 6 hours and nocturnal temperature between 18 and 22°C (Blum and Dianese, 2001; CABI, 2015; Tessman et al., 2001).

Dispersal and spread: Rust spores are wind-dispersed over long distances.  Long and short distance spread is through rust-contaminated planting material, nursery stock, cuttings, flowers, timber, wood packaging, equipment, tools, and human clothing/contact.  Foraging honey bees, bats, and birds in contact with rust spores have vectored the pathogen to uninfected host plants (Carnegie et al., 2010).  Under sub-optimal conditions, the pathogen can remain in non-symptomatic plants for 4-6 weeks before symptoms are visible, thereby enabling undetected spread to non-infected regions (Carnegie & Lidbetter, 2012)

Hosts:  Several genera and species belonging to the order Myrtales, in the family Myrtaceae. The natural and experimental global host list for Puccinia psidii includes 445 species in 73 genera and 16 tribes of the family Myrtaceae.  However, a large proportion of these hosts are known only as experimental hosts (CABI, 2015).  Primary hosts include genera and species of: Agonis flexuosa (willow myrtle), Eucalyptus spp., E. dunnii, E. globulus, E. gracilis, Eugenia spp., Eugenia uniflora (Surinam cherry), Melaleuca spp., Melaleuca quinquenervia (paperbark), Metrosideros polymorpha (ohi’a), Myrtus communis (myrtle), Pimenta spp., Pimenta dioica (allspice), Psidium spp., Psidium guajava (guava), Syzygium jambos (Malabar plum), S. samarangense (wax apple), Rhodonyrtus tomentosa (rose myrtle) (CABI, 2015; EPPO, 2015).  Other hosts are also included in the genera of Myrtaceae: Actinostemon, Asclepias, Callistemon, Calycorectes, Campomanesia, Jambosa, Marlierea, Metrosideros, Myrcia, Myrciaria, Myrceugenia, Pseudomyrcianthes, Psidiopsis, and Syzygium (Farr & Rossman, 2015).

Symptoms and damage potential:  Symptoms vary depending on the host species, level of susceptibility within a host species and age of host leaf.  Actively growing, young leaves, stems, and shoot tips, also fruit, sepals, and flowers are susceptible to P. psidii infection.  Initial symptoms of rust infections appear two to four days after infection as tiny chlorotic specks that develop into 0.1-0.5 mm-diameter spots or pustules (uredinia).  Uredinia occur in groups on leaves (commonly on the underside, but not always), on stems, flowers and fruit.  After a few days, these pustules erupt due to the production of bright yellow to orange-yellow urediniospores.  The infected area or spots expand and multiple pustules merge over time.  Older lesions have purple margins on leaves and shoots of many Eucalyptus, Melaleuca and Callistemon hosts.  Infected plant tissue becomes necrotic. If left untreated, disease-affected plants result in deformed leaves, heavy defoliation of branches, stunted growth, dieback, and eventually, death (CABI, 2015; Glen et al., 2007).

Puccinia psidii can cause significant losses to economically important young tree crops, such as, Eucalyptus spp., and other environmental trees in Myrtaceae – including myrtle and paperbark.  Severe disease infections on foliage, inflorescences, and young succulent fruits can seriously impact guava production causing defoliation, death of shoot tips, and mummified fruit (Glen, et al., 2007; Hernandez, 2006).  80-100% loss of guava production was been reported in Brazil (CABI, 2015).

Worldwide Distribution: Asia: China, Japan; Africa: South Africa; North America: Mexico, USA; Central America and Caribbean: Costa Rica, Cuba, Dominica, Dominican Republic, Guatemala, Jamaica, Panama, Puerto Rico, Trinidad and Tobago, United States Virgin Islands and British Virgin Islands; South America: Argentina, Brazil, Colombia, Ecuador, Paraguay, Uruguay, Venezuela; Oceania: Australia, New Caledonia.   Records of the absence of Puccinia psidii from India and Taiwan are considered unreliable (CABI, 2015; EPPO, 2015).

In the USA, Puccinia psidii is considered an invasive species that has been reported from Florida, Hawaii, and California (CABI, 2015).

Official Control: Puccinia psidii has recently been made federally actionable for imports destined for Hawaii, however, domestic shipments are not affected (CABI, 2015).  Puccinia psidii is on the Harmful Organism List for the following countries: Mexico, Morocco, Nambia, New Zealand, South Africa, and Vietnam (USDA-PCIT, 2015).  In 2007, it was declared a Quarantine pest in Jordan (EPPO, 2015).  Currently, P. psidii is a B-rated pathogen in California.

California Distribution:  Puccinia psidii has been detected in nursery stock in Contra Costa, Orange, San Diego, San Francisco, Santa Barbara, Santa Clara, and Santa Cruz Counties.

California Interceptions: Puccinia psidii has been detected in several interceptions of infected nursery stock shipped from Hawaii and Florida.

The risk Myrtle Rust 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 Myrtle rust pathogen is already established in California and is suspected to be present wherever Myrtaceae host plants are grown in nurseries and natural environments.  These environments include mainly coastal 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 High (3):  Puccinia psidii has a wide host range of over 400 species within the plant family Myrtaceae.  However, a large proportion of these hosts are experimental ones.  Main hosts included in several genera listed under “hosts” in the above text.  While several strains of the pathogen are known to exist, exhibiting different virulence and host specificities, at least one strain attacking Melaleuca quinquenervia (paperbark) is known to occur in outdoor environments in California.  Planted Melaleuca is common in coastal southern California.  Other Myrtaceae hosts present in the State, such as Eucalyptus, may also be at risk although the rust pathogen has not been reported on Eucalyptus 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): Puccinia psidii has high reproduction and dispersal potential via its windblown spores that are capable of being transmitted by strong winds over distances of several hundred kilometers.  Also they may be spread over long distances via infected nursery stock, cuttings, flowers, timber, wood packaging, equipment, tools, and human clothing/contact.  Other agents of spread include foraging honey bees, bats, and birds in contact with rust spores.  Under sub-optimal conditions, the pathogen can remain in non-symptomatic plants for 4-6 weeks before symptoms are visible, thereby enabling undetected spread to non-infected regions.  The pathogen has already spread from nursery sites to outdoor natural environments within California.

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): The presence of Puccinia psidii in California is already a quarantine issue for exports of Myrtaceae hosts destined for Hawaii, as well as an actionable concern to some other non Myrtle rust-infected countries. Furthermore, rust infections could result in lowered crop value, yield and altered cultural practices in nursery grown plants.  The fungus can be vectored to non-infected hosts by insects and larger animals contaminated with spores.

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:

– 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):  Puccinia psidii infections could affect growth of hosts within Myrtaceae. There are several species within Myrtaceae which are listed as endangered and may potentially by threatened by the fungus.  However, reports of Myrtle rust affecting these other host plants established in outdoor environments in California is currently not known. 

Consequences of Introduction to California for Myrtle Rust:

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 = 13 (High).

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).  Puccinia psidii has been detected in nursery stock in Contra Costa, Orange, San Diego, San Francisco, Santa Barbara, Santa Clara, and Santa Cruz Counties.  It has also been detected in outdoor environments in San Diego County as well as suspected to have spread to outdoor environments of the above listed 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 = 10 (Medium).

Uncertainty:

Puccinia psidii is a quickly spreading rust pathogen that is very difficult to eradicate manly due to its ease of long distance dispersal and broad host range.  It is already established in outdoor environments within the State.  More information on its parasitism of different plant species in California will increase current knowledge of host range and further strengthen its proposed rating.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Puccinia psidii is C.

References:

Blum L. E. B., and J. C. Dianese .  2001.  Patterns of urediniospores release and development of rose apple rust. Pesquisa Agropecuaria Brasileira 36: 845–850.

Carnegie, A. J. and J. R. Lidbetter.  2012.  Rapidly expanding host range for Puccinia psidii sensu lato in Australia. Australasian Plant Pathology, 41(1):13-29. http://www.springerlink.com/content/w8538 mu25rh72870/fulltext.html.

Carnegie, A. J., J. R. Lidbetter, J. Walker, M. A. Horwood, L. Tesoriero, M. Glen, and M. J. Priest.  2010.  Uredo rangelii, a taxon in the guava rust complex, newly recorded on Myrtaceae in Australia. Australasian Plant Pathology, 39(5):463-466. http://www.publish.csiro.au/nid/39.htm.

EPPO.   2015.  Puccinia psidii (PUCCPS).  PQR database.  Paris, France: European and Mediterranean Plant Protection Organization.  http://www.newpqr.eppo.int

Farr, D. F. and A. Y. Rossman, Fungal databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA.  Retrieved August 24, 2015 from http://nt.ars-grin.gov/fungaldatabases/.

Glen, M., A. C. Alfenas, E. A. V. Zauza, M. J. Wingfield and C. Mohammed.  2007.  Puccinia psidii: a threat to the Australian environment and economy – a review.  Australasian Plant Pathology, 36: 1-16.

Hernandez, J. R.   2015.  Invasive fungi, Puccinia psidii.  Systematic Mycology and Microbiology Laboratory, ARS. USDA.  27 February 2006. Retrieved July 30, 2015, from /sbmlweb/fungi/index.cfm .

Killgore, E. M. and R. A. Heu.  2007.  A rust disease on ‘Ohi’a, Puccinia psidii Winter. New Pest Advisory 05-04 (Updated December 2007). Honolulu, Hawaii, USA: Hawaii Department of Agriculture. http://www.hawaiiag.org/hdoa/npa/npa05-04-ohiarust.pdf

Marlatt, R. B. and J. W. Kimbrough.  1979.  Puccinia psidii on Pimenta dioica in south Florida. Plant Disease Reporter, 63(6):510-512.

Mellano, V.  2006.  Rust on myrtle found in San Diego County. Healthy Garden-Healthy Home. University of California Cooperative Extension Retail Nursery Newsletter, 1:3

Roux,  J., I. Greyling, T. A. Coutinho, M. Verleur, M. J. Wingfield.  2013. The Myrtle rust pathogen, Puccinia psidii, discovered in Africa. IMA Fungus, 4(1):155-159. http://www.imafungus.org/Issue/41/24.pdf.

Tessmann, D. J., J. C. Dianese, A. C. Miranda, and L. H. R. Castro.  2001.  Epidemiology of a Neotropical rust (Puccinia psidii): periodical analysis of the temporal progress in a perennial host (Syzygium jambos). Plant Pathology 50, 725–731. doi: 10.1046/j.1365-3059.2001.00646.x

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

Zambino, P. J., and P. A. Nolan.  2011.  First report of rust caused by Puccinia psidii on paperbark, Melaleuca quinquenervia, in California.  Plant Disease, 95:1314. http://dx.doi.org/10.1094/PDIS-05-11-0436.

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.

Final Pest Rating:  C

Posted by ls

Fungi, Plant Pathogens

Tranzschelia mexicana M. Scholler & M. Abbasi

California Pest Rating for
Tranzschelia mexicana M. Scholler & M. Abbasi
Pest Rating: B
PEST RATING PROFILE
Initiating Event:

During April, 2015, Heather Scheck, plant pathologist, Santa Barbara County Agricultural Commissioner’s office detected symptoms of rust on capulin cherry nursery stock growing in a nursery in Santa Barbara County.  Cheryl Blomquist, CDFA plant pathologist, examined infected leaf samples and identified the associated rust pathogen Tranzschelia mexicana.  This pathogen was first found in Santa Barbara in 2014 in 4 year old cherry trees grown in a residential backyard garden.

History & Status:

Background:  Tranzschelia mexicana is a fungal pathogen that causes rust in capulin cherry trees.  The pathogen was originally described from Mexico and thus named to indicate its natural distribution in southern Mexico.  It is assumed that this pathogen requires two different kinds of hosts to complete its life cycle (also called a host alternating rust) and is macrocyclic (i.e., produces urediniospores, teliospores and basidiospores on main host and spermatia and aeciospores on an alternate host).  However, the alternate host as well as spermogonia and aecia (fruiting structures producing spermatia and aeciospores respectively) are unknown for T. mexicana. Furthermore, Blomquist et al. (2015) did not detect telia in rust-infected capulin cherry leaves that were collected from trees in Santa Barbara County, California, during October and November 2014 and January 2015 and thereby, deduced that the fungal species does not form telia.  This is not unusual for host alternating rusts when aecial hosts (alternate hosts) are not present in regions. Scholler et al., suggest that Anemone mexicana – a plant native to the Valley of Mexico – might be the aecial host for the capulin rust pathogen.  Nevertheless, it is likely that T. mexicana has spread without its aecial host via production of urediniospores only (Scholler et al., 2014).

Hosts: Capulin/Mexican black cherry, (Prunus salicifolia, Rosaceae) is the only reported host for Tranzschelia mexicana (Scholler et al., 2014; Blomquist et al., 2015).

Symptoms: Tranzschelia mexicana causes yellow spots on the upper side of leaves and brownish pustules on the underside.  Entire infected trees are susceptible to high infestations although fewer pustules may be present in younger leaves than older leaves.  Severe infestations may cause defoliation and reduced plant stands (Blomquist et al., 2015).

Damage Potential:  Capulin cherry is not a commercially cultivated crop in California, however, a small percentage of nursery stock plants are sold in the retail market.  Infections of this rust pathogen could negatively impact production and value of plants in private residences, public parks, amusement parks, and other environments. Rusted capulin cherry leaves are not only aesthetically unsightly but also negatively impact plant growth.  Severe infestations of rust can result in defoliation and reduction in plant growth, vigor and stand.  Containment and management of the rust pathogen can be difficult as infected leaves produce masses of air-borne spores enabling long-range spread and infection.

Transmission:  The pathogen is spread from plant to plant mainly by windblown spores.  Urediniospores can be transported over several hundred kilometers by strong winds and washed down by rain to available hosts.  Insects, animals, humans, and rain may also aid in spreading spores to non-infected plants. Infected nursery plants also aid in introducing and spreading the pathogen.

Worldwide Distribution: North America: Mexico, USA (California – CDFA pest detection records); South America: Colombia, Ecuador (Scholler et al., 2014). It is assumed that the distribution of the capulin rust pathogen extends beyond the above mentioned distribution in the Americas where capulin cherry is cultivated.

Official Control: None reported.

California Distribution:  Capulin rust pathogen, Tranzschelia mexicana, has been detected in residential backyard and nursery environments in Santa Barbara County (see ‘Initiating Event’).

California Interceptions:  There have been no quarantine interceptions of Tranzschelia mexicana was intercepted in California.

The risk Tranzschelia mexicana 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) – Tranzschelia mexicana is able to establish wherever capulin cherry trees are grown in California.  Capulin cherry (Prunus salicifolia) is a rare fruit and is grown in many low chill regions in California for its flowers and edible fruit.

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 Low (1) – Currently the host range of Tranzschelia mexicana is limited to capulin cherry (Prunus salicifolia). The alternate host for this pathogen is not known. Blomquist et al (2015) did not find symptoms of rust on several peaches, apricots and other Prunus spp. that were growing on the same property with rust-infested capulin cherry trees.

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 infective spores of Tranzschelia mexicana namely, urediniospores, are produced in abundance and are spread to healthy plants mainly by wind. Insects, animals, humans, rain, and infected nursery plants also aid in its spread.

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) – Severe infestations of the capulin cherry rust pathogen could result in defoliation and reduction of plant growth, vigor and stand, and loss of markets. Nursery plantings are at risk being significantly impacted by the introduction of this pathogen. Without eradicative action subsequent to detection of bamboo rust-infected plants within greenhouse environments, there is the risk of further spread to the outside environment. The spread of the rust pathogen would be difficult to manage due to its effective means of windblown transmission.

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) – Capulin cherry plantings for aesthetic and rare fruit production value by private growers may be impacted by the capulin cherry rust pathogen subsequently triggering additional treatment programs.

Consequences of Introduction to California for Tranzschelia mexicana

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 Tranzschelia mexicana 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.

Evaluationis Low (-1): Presently, Tranzschelia mexicana is only established in Santa Barbara, 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:

Future detection surveys for Tranzschelia mexicana in nurseries and established capulin cherry plantings are needed to gain further information of the probable introduction, establishment and distribution of this pathogen in California.  This information could alter the proposed rating.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Tranzschelia mexicana is B.

References:

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

Blomquist, C. L., M. Scholler and H. J. Scheck.  2015.  Detection of rust caused by Tranzschelia mexicana on Prunus salicifolia in the United States.  Plant Disease (Accepted for publication).

California Rare Fruit Growers, Inc.  1997. Capulin cherry Prunus salicifolia HBK. Fruit Facts. http://www.crfg.org/pubs/ff/capulin-cherry.html .

Scholler, M., M. Abbasi and F. Friedrich.  2014.  Tranzschelia in the Americas revisited: two new species and noted on the Tranzschelia thalictri complex.  Mycologia, 106: 448-455. DOI: 10.3852/12-260.

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

Podosphaera caricae-papayae

California Pest Rating for
Podosphaera caricae-papayae
Pest Rating: B
PEST RATING PROFILE
Initiating Event: 

In March 2014, Podosphaera caricae-papayae, a powdery mildew fungal pathogen, was identified by morphological and sequence analyses by Suzanne Latham, plant pathologist, CDFA. The symptomatic papaya leaf sample was collected from an ornamental container nursery in Santa Barbara County by County Agricultural plant pathologist, Heather Scheck. The identity of the pathogen was confirmed by USDA APHIS PPQ Mycologist, Megan Romberg.  Subsequently, the nursery destroyed the infected papaya plants.  In May 2014, the same pathogen was detected on papaya plants, grown in a commercial papaya fruit production nursery greenhouse at a different location within Santa Barbara County.  The detection of powdery mildew of papaya in Santa Barbara County marks a first record for North America.  Initially, the fungal pathogen was assigned a Q rating which is reassessed herein for the proposal of a permanent rating.

History & Status:

Background:    Podosphaera caricae-papayae was originally described by Tanda and Braun in 1985 as Sphaerotheca caricae-papayae.  However, in 2000 the species was placed in the genus Podosphaera based on molecular sequence analysis by Braun and Takamatsu (Romberg, 2014).  Complications in taxonomic classification of the species exist over the accurate linkage of the sexual or teleomorph stage to the asexual or anamorph stage of the pathogen and further molecular and morphological studies are needed to determine the correct taxonomic position of P. caricae-papayae.  In the original description of the species, the teleomorph stage, Sphaerotheca, was linked to the anamorph stage, Oidium caricae (Liberato et al., 2004).  However, later this linkage was proven inaccurate and O. caricae was rejected as the anamorph stage, thereby leaving the classification of an asexual stage for P. caricae-papayae unresolved.  The exact distribution is unknown because it is unclear which records of “O. caricae” actually belong to P. caricae-papayae.  In 2012, P. caricae-papayae was synonymized with the morphologically similar species P. xanthii – the pathogen causing powdery mildew on cucurbits (Braun & Cook, 2012).  The synonymy of P. xanthii and P. caricae-papayae is in question given recent molecular work (Takamatsu et al., 2010).  P. caricae-papayae is only known from infected seedlings of papaya in Australia, China, India, Japan, New Zealand and California (USA).  Greenhouse infections of papaya plants in California were reported as being caused by “cucurbit powdery mildew”.  Infections of mature papaya plants in the field have never been reported.

The infected papaya plants recently detected in California only bear the anamorph stage which morphologically resembles the anamorph stage of P. caricae-papayae that was described by Tanda and Braun in 1985 (Romberg, 2014).  Furthermore, molecular sequence analysis revealed that the sequences from both California detections are identical to a sequence of P. caricae-papayae from Thailand that was used by Takamatsu et al., (2010) in their phylogenetic analyses of the genus Podosphaera (Latham, 2014; Romberg, 2014).  Unfortunately, no morphological information of the Thailand isolate is available to compare with the California isolate.  The sequence from Thailand is the only P. caricae-papayae sequence deposited in GenBank and therefore, analytical sequence comparisons of isolates of P. caricae-papayae from California and Thailand with those from other reported regions are lacking.  Nevertheless, the Thailand sequence is different from other Podosphaera species sequences in Genbank, including the cucurbit powdery mildew, P. xanthii.   Further molecular and morphological studies which would include more isolates will help determine the correct taxonomic position of P. caricae-papayae within the genus Podosphaera in the family Erysiphaceae of the order Erysiphales (Takamatsu et al., 2010).

Powdery mildew of papaya is on obligate parasite.  The fungus grows on the surface of plant tissue and invades by sending feeding organs (haustoria) into the plants epidermal cells only in order to obtain nutrients.  Mycelium produces conidiophores on the plant surface.  Each conidiophore produces chains of conidia (spores) that are dispersed by air currents.  Powdery mildew thrives in warm and humid environments. Low light levels, high humidity, moderate temperature and rainfall enhance disease development in papaya (Cunningham & Nelson, 2012). Generally, disease can be severe in warm and dry climate as long as the relative humidity is high enough to enable condial germination and infection.

Hosts: Carica papaya (papaya).

Symptoms:  Powdery mildew infects papaya plants of all ages however seedlings in greenhouses are more susceptible than field grown plants.  The pathogen frequently infects young immature leaves, petioles, pedicels, peduncles, and unripe fruit. Early on, the undersides of leaves become speckled with small water-soaked spots with white to grayish powdery fungal patches usually near the leaf veins.  Yellow-green spots develop on the corresponding upper sides.  Soon the patches grow in size and coalesce, and fungal growth may grow on the upper leaf surface and veins.  In severe infections, leaves become necrotic, curl and drop prematurely.  Mildew patches also develop on immature fruit and can cover the entire fruit, eventually resulting in deformed fruit (Cunningham & Nelson, 2012).

Damage Potential:  Infections can result in prematurely defoliated trees, mildewed and deformed fruit causing significant if not, total losses in plant growth and crop yield.   Deformed fruit is not marketable resulting in lowered sales.  Infections occurring in plants grown in greenhouse can result in severe spread and loss in production if left unmanaged.

In California, there is no commercial acreage under cultivation for papaya. Production is limited to ornamental and fruit production nursery greenhouse and residential gardens for ornamental purposes in southern California counties.  Under those environments, loss in production is possible if not managed.

Transmission:  Conidia (spores) are primarily dispersed by wind currents.

Survival:  During cool weather, condia production ceases and powdery mildew fungi overwinter as cleistothecia (a sexually produced, closed, fruiting body) and mycelium in dormant plant tissue. However, only the asexual stage has been found in California greenhouses.  Constant greenhouse growth conditions could perpetuate the anamorphic stage of the fungus.

Worldwide Distribution: The true distribution of the California isolate of P. caricae-papayae is currently not known.  Molecular sequence analyses remain unknown for reported isolates of P. caricae-papayae from Australia, China, India, Japan, and New Zealand.  The sequence of the isolate from Thailand is the only one deposited in GenBank, and is identical to the sequence of the California isolate.

Official Control:  There is no record of official control against this pathogen.

California Distribution: The pathogen has only been detected in greenhouses of two nurseries at two different locations in Santa Barbara County.

California Interceptions:  There are no records of Podosphaera caricae-papayae having been intercepted in papaya imported to California.

The risk Podosphaera caricae-papayae 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 Low (1) – Of what is currently known, Podosphaera caricae-papayae will only infect papaya and therefore, is limited to wherever papaya is cultivated.  In California, where there is no major cultivation of papaya, plants are propagated in greenhouses for fruit production and ornamental plantings in residential and urban environments of southern counties.  As evident in the recent detection in Santa Barbara, the pathogen is capable of establishing in nursery grown papaya.  

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 Low (1) – The host range is limited to Carica papaya (papaya).

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) – Under suitable climate conditions, airborne conidia are produced in abundance and readily spread by wind currents to non-infected sites.  Within and outside greenhouse environments, the pathogen is capable of rapidly spreading to non infested papaya plants as well as other sites where papaya is grown.

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 can potentially cause significant losses in plant growth and crop yield. Powdery mildew infections of papaya fruit could lower crop yield and value causing significant losses in production.  This would result in loss of markets, and change in cultivation practices to prevent the spread of inocula to non-infected, healthy 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) – Although limited to papaya, occurrence of the pathogen in nursery and outside environments could significantly impact home/urban gardening and/or ornamental plantings, as well as result in the imposition of additional official or private treatments to mitigate effects of infection.

Consequences of Introduction to California for Podosphaera caricae-papayae:

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 P. caricae-papayae 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).  The pathogen was only detected within nursery greenhouses in Santa Barbara, California.  Measures were taken to destroy infested plants.

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:

To date, the detection of P. caricae-papayae in California is limited to two in-greenhouse sites in Santa Barbara County.  There have not been any additional detections, surveys or reports of new infestations in papaya production nurseries and/or outside environments to provide further knowledge of the presence of this pathogen. Further comparative molecular analyses against reported international isolates of the pathogen may provide information of its global distribution and clarity of its taxonomic classification, however, it’s separation from P. xanthii (present in California) has already been proven (see ‘Background’).

While the host range and distribution of the pathogen within California is currently known to be limited, the potential of incurring significant damage due to infection by P. caricae-papayae places the limited distribution of instate papaya nursery ornamental and production plants at medium risk and, therefore, warrants assignment of a B rating.  Future detections of P. caricae-papayae could indicate a wider distribution than presently known and result in a lower rating.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Podosphaera caricae-papayae is B.

References:

Braun, U. and R. T. A. Cook.  2012.  Taxonomic manual of the Erysiphales (Powdery Mildews).  Centraalbureau voor Schimmelcultures, vol. 11, 707 p.

Cunningham, B and S. Nelson.  2012.  Powdery mildew of Papaya in Hawai’i.  College of Tropical Agriculture and Human Resources University of Hawai’I at Mānoa.  Plant disease, PD-90.

Latham, S.  2014.  Email to John Chitambar, CDFA: sent July 3, 2014.

Liberato, J. R., R. W. Barreto and R. P. Louro.  2004. Streptopodium caricae sp. nov., with a discussion of powdery mildews on papaya, and emended descriptions of the genius Streptopodium and Oidium caricae.  Mycological Research 108:1185-1194.

Romberg, M. K.  2014.  Email from M. K. Romberg, APHIS-USDA, to Suzanne Latham, CDFA: sent March 26, 2014.

Takamatsu, S., S. Ninomi, M. Harada and M. Havrylenko.  2010.  Molecular phylogenetic analyses reveal a close evolutionary relationship between Podosphaera (Erysiphales: Erysiphaceae) and its rosaceous hosts.  Persoonia, 24, 38-48.

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 boninense Moriwaki, Toy. Sato & Tsukib. 2003

California Pest Rating for
Colletotrichum boninense Moriwaki, Toy. Sato & Tsukib. 2003
Pest Rating: B
PEST RATING PROFILE
Initiating Event:  

During February 2015, the fungal pathogen Colletotrichum boninense was detected in infected Aglaonema commutatum (Aglaonema/Chinese evergreen) cuttings in a nursery in Vista, San Diego County, California.  The plants were part of an incoming nursery shipment from Fallbrook, San Diego County, California and originated in a nursery in Costa Rica. A month later, the pathogen was detected twice in San Diego in two different shipments of Aglaonema sp. plants: one sent to the Vista nursery by the same shipper as before, and the other sent by a different shipper to a different nursery.  The latter two shipments had also originated in Costa Rica.  The pathogen was cultured from leaf spots, sequenced, and identified by Suzanne Latham, CDFA plant pathologist.  This detection was considered a new US record and reportable by the USDA. The species identity was confirmed by the USDA PPQ National Mycology Laboratory.  Consequently, the shipment of plants was destroyed.   A permanent rating for Colletotrichum boninense is proposed herein.        

History & Status:

Background:  Colletotrichum boninense was first discovered associated with Crinum asiaticum var. sinicum (Amaryllidaceae) in the Bonin Islands, Japan (Moriwaki et al., 2003).  These scientists also found the species in Japan to be associated with several other hosts plants of different plant families.  Furthermore, C. boninense was originally described in 2003 as a segregate of the vastly morphological and physiological variable C. gloeosporioides complex (CABI, 2014; Morikwaki et al., 2003).  Prior to its segregation as a species, isolates of C. boninense were often identified as C. gloeosporioides.  However, after the segregation, 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. boninense in its strict sense (s. str.) based on DNA sequence data and morphology.  The current proposed rating is for C. boninense s. str.

Hosts: Host plants of C. boninense s. str. are very diverse and include members in the plant families Amaryllidaceae, Bignoniaceae, Podocarpaceae, Proteaceae, Solanaceae and Theaceae (Damm et al., 2012).  The CDFA 2015 detection of C. boninense s. str. on Aglaonema commutatum would also include the family Araceae.

The range of host plants for Colletotrichum boninense s. str. is not well understood from reports published prior to 2012 as many of those reports refer to the broad C. boninense complex (sensu lato).  Subsequently, those reported hosts would need to be molecularly verified to be C. boninense s. str.  and include members of the genera Bletilla, Camellia, Capsicum, Cattleya, Clivia, Coffeae, Crinum, Cucumis, Cymbidium, Dacyrarpus, dendrobium, Dracaena, Eucalyptus, Hippaestrum, Leucospermum, Oncidium, Pachira, Panax, Passiflora, Pleione, Protea, Prunus, and Solanum (Farr & Rossman, 2015).

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

Damage Potential:  Anthracnose disease caused by Colletotrichum boninense can result in reduced plant quality and growth.  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 boninense 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.  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, Brazil, China, Colombia, Japan, Korea, the Netherlands, New Zealand, South Africa, and Zimbabwe (Farr & Rossman, 2015).

Except for Japan, Australia, and New Zealand where the presence of Colletotrichum boninense s. str. was verified (Damm et al., 2012), reports from other countries should be independently verified for C. boninense s. str.

The 2010 report of Colletotrichum boninense in Florida, USA, reported by Tarnowski & Ploetz,  is now not considered to be C. boninense s. str. but actually a different species within the C. boninense species complex (personal communication: Aaron Kennedy, National Identification Services, USDA-APHIS-PPQ-PM). The Florida report was published before the C. boninense complex was split into several species in 2012.

Official Control:  Colletotrichum boninense is considered a new USA record and reportable to the USDA.

California Distribution: There is no official record of the establishment of Colletotrichum boninense in California however during the early 1980s, CDFA plant pathologists identified C. gloeosporioides in Camelia japonica (Theaceae) and other hosts in the plant family Araceae which are included as host for C. boninense s. str.  These detections were made in northern and southern coastal counties.  At that time specific molecular diagnostic tests were not available to enable the distinction of C. boninense.  It is, therefore, possible that these detections may have included C. boninense s. str. (Suzanne Latham and Cheryl Blomquist, CDFA, personal communication).  No eliminative action would have been taken against C. gloeosporioides as the species is known to be widespread in California.

California Interceptions:  Colletotrichum boninense has been intercepted at least thrice in shipments of Algaonema sp. from Costa Rica (see ‘Initiating event’).

The risk Colletotrichum boninense 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. boninense 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. Limited regions with conducive climates within California could enable the pathogen to establish.  In particular, C. boninense s. str. can 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:

– 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 boninense s. str. is very diverse and includes member in the plant families Amaryllidaceae, Bignoniaceae, Podocarpaceae, Proteaceae, Solanaceae, Theaceae, and Araceae.

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 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 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) – 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 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) – The pathogen could significantly impact cultural practices, home gardening or ornamental plantings.

Consequences of Introduction to California for Colletotrichum boninense:

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 boninense 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 not established.  However, while there is no official record of the establishment of Colletotrichum boninense in California, during the 1980s, CDFA plant pathologists identified C. gloeosporioides in Camelia japonica (Theaceae) and other hosts in the plant family Araceae which are included as host for C. boninense s. str.  These detections were made in northern and southern coastal counties.  At that time specific molecular diagnostic tests were not available to enable the distinction of C. boninense.  It is, therefore, possible that these detections may have included C. boninense s. str.

Final Score:

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

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

Uncertainty:

The possibility that the 2013 detection of C. gloesporoides may have included the now segregate species, C. boninense st. str. and that the latter may already be established in California, can only be ascertained through survey and testing of infected host plants particularly in suspect counties included in early detection reports of C. gloeosporioides .  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 boninense s. str. is B.

References:

CABI.  2014.  Colletotrichum boninense datasheet report.  Crop Protection Compendium.  www.cabi.org/cpc/

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.

Tarnowski, T. L. B. and R. C. Ploetz.  2010.  First report of Colletotrichum boninense, C. capsici, and a Glomerella sp. as causes of postharvest anthracnose of passion fruit and Florida.  Plant Disease 94:786. http://dx.doi.org/10.1094/PDIS-94-6-0786C .

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