Category Archives: Plant Pathogens

Plant Pathology (plant diseases)

Fungi, Plant Pathogens

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

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

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

History & Status:

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

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

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

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

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

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

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

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

California Interceptions: None reported.

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

Consequences of Introduction: 

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

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

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

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

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

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

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

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

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

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

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

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

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

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

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

A. The pest could lower crop yield.

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

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

D. The pest could negatively change normal cultural practices.

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

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

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

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

– Medium (2) causes 2 of these impacts.

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

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

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

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

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

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

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

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

Score the pest for Environmental Impact. Score:

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

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

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

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

Consequences of Introduction to California for Ascochyta aquilegiae:

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

-Low = 5-8 points

–Medium = 9-12 points

-High = 13-15 points

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

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

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

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

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

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

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

Final Score:

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

Final Score:  Score of Consequences of Introduction – Score of Post Entry Distribution and Survey Information = 8.

Uncertainty:   

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

Conclusion and Rating Justification:

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

References:

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

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

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

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

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

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

Responsible Party:

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

Comment Format:

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

Example Comment: 

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

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

♦  Comments may not be posted if they:

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

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

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

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

Pest Rating:  C

Posted by ls

Fungi, Plant Pathogens

Puccinia kuehnii (W. Krűger) E. J. Butler 1914

California Pest Rating for
Puccinia rusts. Photo credit: Cesar Calderon, USDA APHIS PPQ. Bugwood.org
Puccinia rusts. Photo credit: Cesar Calderon, USDA APHIS PPQ. Bugwood.org
Puccinia kuehnii (W. Krűger) E. J. Butler 1914
Pest Rating:  C
PEST RATING PROFILE
Initiating Event:

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

History & Status:

Background:  Puccinia kuehnii is one of two major rust fungi on sugarcane and causes orange rust.  The other rust fungi known as P. melanocephala, causes brown rust and is relatively common.  The orange rust of sugarcane pathogen, P kuehnii, most likely originated in Asia-Oceania regions where Saccharum spp. are native.  In other countries where the pathogen occurs, such as Indonesia and the South Pacific, sugarcane has existed for several centuries and it is assumed that P. kuehnii was likewise introduced and also existed in those countries for the same period of time.  The pathogen is now wide spread in Asia and Australia and was recently discovered in West Africa and the Western Hemisphere and from sugarcane-growing regions in the southeastern United States, Central and South America, and the Caribbean Basin (Dixon & Castlebury, 2016). It is likely that the pathogen was introduced to Australia along with sugarcane that was introduced about 150 years ago as there are no known native hosts present in that region (CABI, 2016).  In the USA, P. kuehnii was first reported from Florida having been detected in infected, brown rust-resistant, sugarcane cultivars. The disease appears to be distributed widely in the South Florida sugarcane-growing region (Comstock et al., 2008).  In 2013, orange rust was also reported from the southern region of Louisiana’s sugarcane production area (Grisham, et al., 2013).  Puccinia kuehnii has not been reported from California nor is sugarcane a major production crop of the State.

Disease cycle:  Puccinia kuehnii completes its life cycle on the same host and has an incomplete lifecycle. Spermagonia and aecia spore states are unknown.    Urediniospores are produced abundantly under natural conditions, but the production of teliospores and basidiospores are comparatively less common.    Under favorable conditions of humidity and temperature, urediniospores present on host germinate to penetrate the tissue.  As the fungus grows, uredinia (fruiting structures) are formed and urediniospores are produced in abundance.   Urediniospores are produced between 10°C and 34°C and optimally at 15-25°C for urediniospores and 26°C for teliospores.  Relative humidity above 97% favors urediniospore germination (Hsieh & Fang, 1983; CABI, 2016).

Dispersal and spread: The main risk for natural dispersal of spores over long distances (over 2000 km) is by wind and wind-blown rain.  Other potential means for spread are the movement of infected leaves and spore-contaminated clothing (CABI, 2016).

Hosts:  Saccharum officinarum (sugarcane) is the main host.  Other hosts include few weeds and ornamental grasses belonging to Saccharum spp. within Poaceae: Saccharum arundinaceum, S. barberi, S. bengalense, S. edule, S. munja, S. narenga, S. rufipilum, S. sinense, S. spontaneum; S. ravennae (syn. Erianthus ravennae); Sclerostachya fusca (Afshan & Khalid, 2013; CABI, 2016; Dixon & Castlebury, 2013; EPPO, 2016; Farr & Rossman, 2016 )

Symptoms:  Orange rust disease is characterized by the development of lesion that initiate as small (0.5 mm diameter) spots on leaves and enlarge into elongated brown lesions (2-8 mm x 0.5-2 mm wide).  As the lesions enlarge, fungal mycelium protrudes through the leaf surface, usually on its underside, producing abundant urediniospores. These pustules usually occur in patches or groups, but cover entire leaf surfaces in severe infections. Severely infected leaf tissue becomes necrotic leading to early senescence. Affected crops appear brown with very little green tissue remaining at all. Symptom development may take 3-4 weeks from infection, depending on weather conditions (CABI, 2016).

Disease Potential:  Orange rust of sugarcane is considered a disease of low economic impact that has rarely caused significant economic losses.  The only severe economic loss was reported in Australia in 2000 on the introduced, highly susceptible Q124 sugarcane variety that was subsequently replaced (CABI, 2016).  The potential for establishment and spread of the pathogen in California is reasonably low as sugarcane, the main host, is grown in limited acreage in dry climates of the Imperial Valley.

Worldwide Distribution: Africa: Cameroon, Cote d’Ivore; Asia: China, India, Indonesia, Japan, Malaysia, Myanmar, Nepal, Pakistan, Philippines, Singapore, Sri Lanka, Taiwan, Thailand, Vietnam; Central America and Caribbean:  Costa Rica, Cuba, Dominican Republic, Guatemala, Jamaica, Nicaragua, Panama; North America: USA, Mexico; South America: Brazil, Colombia, Ecuador; Oceania: American Samoa, Australia, Cook Islands, Fiji, French Polynesia, Guam, Micronesia, New Caledonia, Papua New Guinea, Samoa, Solomon Islands (CABI, 2015; Dixon & Castlebury, 2013; EPPO, 2016; Farr & Rossman).

In the USA it has been reported from Florida and Louisiana (Comstock et al., 2008; Grisham et al., 2013).

Official Control: Puccinia kuehnii is on the “Harmful Organisms Lists” for Brazil, Costa Rica, Egypt, Honduras, and Morocco (PCIT, 2016). Currently, the pathogen has not been rated for California.

California Distribution:  Puccinia kuehnii is not established in California.

California Interceptions: None reported.

The risk Orange Rust of Sugarcane 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):   The potential for establishment and spread of the orange rust pathogen in California is likely to be low as sugarcane, the main host, is grown in limited acreage under dry climates of the Imperial Valley.  Spore germination and plant infection are not expected to be favored under climates of low relative humidity common to that region.

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):  Sugarcane is the main host of P. kuehnii.  The pathogen is largely limited to Saccharum spp. and the related species Sclerostachya fusca.    

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 kuehnii has high reproduction and dispersal potential via its windblown spores that are primarily transmitted by strong winds over distances of several hundred kilometers.  Also, they may be spread over long distances via infected plant leaves and spore-contaminated human clothing. 

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): The economic impact of Puccinia kuehnii to California is considered low as the potential for establishment and spread of the pathogen is reasonably minimal within a state where sugarcane is not a majorly cultivated crop and requires high relative humidity for pathogen infection.  Potential incidents of the disease occurring under conducive climates could lower crop yield.  

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):  Puccinia kuehnii infections could affect production of ornamental grasses belonging to Saccharum spp. and grown in private and/or public commercial environments.    

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 = 8 (Low).

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).  Puccinia kuehnii is not established in California.

Final Score:

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

Final Score:  Score of Consequences of Introduction – Score of Post Entry Distribution and Survey Information = 8 (Low).

Uncertainty:

None.

Conclusion and Rating Justification:

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

References:

Afshan, N.S., and A. N. Khalid.  2013.  Checklist of the rust fungi on Poaceae in Pakistan. Mycotaxon 125: 1-17.

Comstock, J. C., S. G. Sood, N.C. Glynn, J. M. Shine Jr., J. M. McKemy, and L. A. Castlebury.  2008.  First report of Puccinia kuehnii, causal agent of orange rust of sugarcane, in the United States and Western Hemisphere. Plant Disease, 92(1):175. http://www.apsnet.org.

Dixon, L. and L. Castlebury.  2016.  Systematic Mycology and Microbiology Laboratory, ARS, USDA. . Invasive Fungi. Orange rust of sugarcane – Puccinia kuehnii. Retrieved March 10, 2016, from /sbmlweb/fungi/index.cfm.

EPPO.   2016.  Puccinia kuehnii (PUCCKU).  PQR database.  Paris, France: European and Mediterranean Plant Protection Organization.  http://www.newpqr.eppo.int.

Farr, D. F. and A. Y. Rossman.  2016.   Fungal databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA.  Retrieved August 24, 2016 from http://nt.ars-grin.gov/fungaldatabases/.

Grisham, M. P., J. W. Hoy, J. S. Haudenshield, and G. L. Hartman.  2013.  First report of orange rust caused by Puccinia kuehnii in sugarcane in Louisiana. Plant Disease, 97(3):426-427. http://apsjournals.apsnet.org/loi/pdis.

Hsieh, W. H., and F. G. Fang.  1983.  The uredospore production of Puccinia melanocephala and Puccinia kuehnii in sugarcanes. Plant Protection Bulletin, Taiwan, 25(4):239-244.

USDA-PCIT.  2016.  United States Department of Agriculture, Phytosanitary Certificate Issuance & Tracking System (PCIT). https://pcit.aphis.usda.gov/PExD/faces/ViewPExD.jsp .

Responsible Party:

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

Comment Format:

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

Example Comment: 

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

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

♦  Comments may not be posted if they:

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

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

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

Violates agency regulations prohibiting workplace violence, including threats.

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

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

Pest Rating:  C

Posted by ls

Fungi, Plant Pathogens

Peronospora digitalidis Gäum, 1923

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

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

History & Status:

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

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

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

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

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

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

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

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

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

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

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

 Consequences of Introduction: 

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

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

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

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

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

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

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

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

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

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

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

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

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

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

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

A. The pest could lower crop yield.

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

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

D. The pest could negatively change normal cultural practices.

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

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

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

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

– Medium (2) causes 2 of these impacts.

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

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

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

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

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

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

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

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

Score the pest for Environmental Impact. Score:

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

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

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

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

Consequences of Introduction to California for Downy mildew of foxglove:

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

-Low = 5-8 points

-Medium = 9-12 points

-High = 13-15 points

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

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

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

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

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

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

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

Final Score:

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

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

Uncertainty:   

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

Conclusion and Rating Justification:

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

References:

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

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

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

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

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

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

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

Responsible Party:

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

Comment Format:

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

Example Comment: 

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

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♦  Comments may not be posted if they:

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

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

Pest Rating: C

Posted by ls

Plant Pathogens, Viruses and viroids

Squash Vein Yellowing Virus (SqVYV)

California Pest Rating for
Squash Vein Yellowing Virus (SqVYV)
Pest Rating:  B
PEST RATING PROFILE
Initiating Event:

None.  The risk of introduction of Squash vein yellowing virus to California is assessed and a permanent rating for SqVYV is herein proposed.

History & Status:

Background:    In 2003 in Hillsborough County, Florida, an unknown virus was detected in squash plants (Cucurbita pepo) exhibiting vein yellowing symptoms and soon after in 2005, this virus was found to cause watermelon vine decline in watermelon plants in Florida (Webb et al., 2003; Adkins et al., 2007).  In 2006, the virus was identified and characterized as a new species, Squash vein yellowing virus.  SqVYV is a whitefly-transmitted member of the genus Ipomovirus in the family Potyviridae which induces necrosis of watermelon stems and petioles resulting in rapid wilt and death of plants at or near harvest. In the field, SqVYV is often detected in watermelon in mixed infections with other viruses (Adkins et al., 2013).

Squash vein yellowing virus was reported from California in 2015 following the fall of 2014 detection of diseased pumpkin plants grown from seed at the University of California Desert Research Extension Center in Holtville, California. Molecular analysis of pathogens associated with the diseased plants revealed mixed infections with the crinivirus Cucurbit yellow stunting disorder virus, the begomovirus Squash leaf curl virus and SqVYV. Symptoms of infection and association of a divergent strain of SqVYV were confirmed through pathogenicity trials and molecular diagnostic tests of infected pumpkin and squash plants.  SqVYV-infected melon plants were also detected in commercial fields in the Imperial Valley (Batuman et al., 2015).   Subsequently, during December 2014, official melon and pumpkin samples from the infected sites were collected by Imperial County Agricultural Commissioner’s staff and sent to CDFA Plant Pathology Laboratory for diagnosis.  Tongyan Tian, CDFA plant pathologist, detected SqVYV from the samples using a RT-PCR protocol and sequence analysis.  The detection of SqVYV in Imperial County marked the first report of an Ipomovirus in California (Batuman et al., 2015).

Hosts: The host range is limited to species in Cucurbitaceae with more dramatic symptoms produced in squash (inc. pumpkin) and watermelon.  Plant hosts include two varieties of cucurbit weeds, namely, Momordica charantia (Balsam-apple) and Melothria pendula (creeping cucumber) (Adkins et al., 2008). The weeds may serve as reservoir hosts for SqVYV.

Symptoms: Initial symptoms consist of a slight yellowing of leaves. This is followed by browning and collapse of entire vines within weeks of the first symptoms.  These symptoms appear as the fruit develops to a harvestable size.  Infected fruit internally often exhibit discolored and necrotic blotches in the rind, discolored flesh (too red) and an off-taste (Baker et al., 2008).  SqVYV-infected cucurbit weed hosts are asymptomatic (Adkins et al., 2008).   In Puerto Rico, symptoms of watermelon vine decline on field-grown watermelon included leaf curling, mosaic, and internode necrosis. During the early stage of plant growth reduced vigor and general stunting occurred, and at the flowering stage, symptoms progressed to necrosis and wilting of vines (Acevedo, et al., 2013).  Adkins et al. (2013) reported that symptoms of vine decline in watermelon appeared 12-16 days after inoculation regardless of plant age at time of inoculation and greenhouse or field location. However, younger watermelon plants exhibited more severe symptoms than older ones.

Damage Potential:  In Florida, watermelon plants suffering from vine decline and fruit rot disease caused by SqVYV has resulted in severe losses in spring and fall plantings.   During this period the disease may rapidly increase in incidence from 10 to >80% within a week (Adkins et al., 2007). The disease can result in total crop loss with collapsed vines and unmarketable fruit with discolored and necrotic rinds.

Transmission:  SqVYV is transmitted by the whitefly Bemisia tabaci.  The pathogen is not transmitted by aphids unlike other common cucurbit-infecting species of the family Potyviridae (Adkins et al., 2003). Experimentally, Adkins and others determined that whiteflies required 1-2 days to feed and acquire the virus from infected plants followed by 2 hours or 2 days to inoculate or transmit the virus to non-infected squash and watermelon plants.  Transmission occurs in a semi-persistent mode by the whitefly which remains infective for 4-6 hours after acquiring the virus.  Adkins et al. (2008) experimentally demonstrated that the whitefly vector was able to acquire SqVYV from inoculated cucurbit weed host Momordica charantia and subsequently transmit it to squash and watermelon to produce typical symptoms.  While the virus has been artificially inoculated to plants under greenhouse conditions, the main mode of natural field transmission is through its whitefly vector.

Worldwide Distribution: North America: USA (California, Florida, Georgia, Indiana, South Carolina, Puerto Rico (Acevedo et al., 2013; Egel & Adkins, 2007; Adkins et al., 2013).

Official Control: Squash vein yellowing virus currently holds a temporary Q rating by the CDFA.  No other official control for SqVYV has been reported.

California Distribution: Currently, Squash vein yellowing virus has only been detected in Imperial County.

California Interceptions:  There are no official records of interceptions of Squash vein yellowing virus in California.

The risk Squash vein yellowing virus would pose to California is evaluated below.

Consequences of Introduction: 

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

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

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

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

Risk is Medium (2) – SqVYV has already been able to establish in Imperial County, southern California  Its further spread to non-infected sites cultivated to cucurbits is limited by the distribution of its vector, Bemisia tabaci, which to date, has not been found in natural cooler climates of northern California counties.

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

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

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

Risk is low (1) – The natural host range is limited to plant species in the family Cucurbitaceae (which are grown extensively in the lower Sacramento Valley and in limited production in San Joaquin and Imperial Valleys). 

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 virus is able to thrive in climates that are favorable for its vector. Its potential for spread is always artificial being completely dependent on the distribution of its vector and infected plant materials.  Therefore, factors that increase movement and activity of the vector and infected plants will also influence that of the virus.  

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) – SqVYV infections could lower crop yield and value, increase production costs, trigger loss of market, and the virus is vectored by the whitefly, Bemisia tabaci which would require implementation of management strategies to minimize the risk of the introduction and establishment of the virus in non-infected regions within California.

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) – Infestations of  SqVYV could significantly impact home/urban gardening of cucurbit host plants resulting in the imposition of additional official or private treatment programs in order to prevent spread of the virus and virus-carrying whitefly vector.

Consequences of Introduction to California for Squash vein yellowing virus

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

-Low = 5-8 points

–Medium = 9-12 points

-High = 13-15 points

Total points obtained on evaluation of consequences of introduction of SqVYV 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). 

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:

While SqVYV is established in the Imperial Valley and there have been no further reports of its spread to other intrastate regions, targeted surveys for the pathogen have not been conducted in other cucurbit production sites.  The distribution and establishment of the virus is largely dependent on the distribution and established infestations of virus-carrying Bemisia tabaci.  Subsequently, detections outside the Imperial Valley may alter the proposed rating for this virus pathogen.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Squash vein yellowing virus is B.

References:

Acevedo, V., J. C. V.  Rodrigues, C. E. de Jensen, C. G. Webster, S. Adkins and L. Wessel-Beaver.  2013.  First report of Squash vein yellowing virus affecting watermelon and bitter gourd in Puerto Rico.  Plant Disease 97:1516.

Adkins S., T. G. McCollum, J. P. Albano, C. S. Kousik, C. A. Baker, C. G. Webster, P. D. Roberts, S. E. Webb and W. W. Turechek.  2013.  Physiological effects of Squash vein yellowing virus infection on watermelon.  Plant Disease 97:1137-1148.

Adkins, S., S.E. Webb, D. Achor, P. Roberts, and C.A. Baker. 2007. Identification and characterization of a novel whitefly-transmitted member of the family Potyviridae isolated from cucurbits in Florida.  Phytopathology 97: 145-154.

Adkins, S.T., S. Webb, C. Baker, and C.S. Kousik. 2008. Squash vein yellowing virus detection using nested polymerase reaction demonstrates the cucurbit weed Momordica charantia is a reservoir host. Plant Disease 92: 1119-1123.

Baker, C., S. Webb and S. Adkins.  2008.  Squash vein yellowing virus, causal agent of watermelon vine decline in Florida. Plant Pathology Circular No. 407, Florida Department of Agriculture and Consumer Services, Division of Plant Industry.

Egel, D. S. and S. Adkins. 2007.  Squash vein yellowing virus identified in watermelon (Citrullus lanatus) in Indiana.  Plant Disease, 91:1056.2.

Batuman, O., E. T. Natwick, W. M. Wintermantel, T. Tian, J. D. McCreight, L. L. Hladky, and R. L. Gilbertson.  2015.  First report of an Ipomovirus infecting cucurbits in the Imperial Valley of California.  Plant Disease 99:1042.  http://dx.doi.org/10.1094/PDIS-12-14-1248-PDN.

Webb, S. E., E. Hiebert and T. A. Kucharek.  2003.  Identity and distribution of viruses infecting cucurbits in Florida.  Phytopathology 93:S89.

Responsible Party:

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

Comment Format:

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

Example Comment: 

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

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

♦  Comments may not be posted if they:

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

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

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

Violates agency regulations prohibiting workplace violence, including threats.

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

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

Pest Rating:  B

Posted by ls

Fungi, Plant Pathogens

Phytophthora tentaculata Kröber & Marwitz 1993

California Pest Rating Proposal for
Phytophthora tentaculata Kröber & Marwitz 1993
Pest Rating: B
PEST RATING PROFILE
Initiating Event: 

During January 2016, samples of two diseased Diplacus hybrids (monkey flower hybrid varieties) and one of diseased Artemisia palmeri (Palmer sagewort) were collected by Kathleen Kosta, CDFA, from a nursery in Santa Clara County.  The samples were processed and analyzed at the CDFA Plant Pathology Laboratory and Phytophthora tentaculata was tentatively identified as the associated pathogen by Suzanne Rooney-Latham, CDFA plant pathologist.  The identity of the pathogen was later confirmed by the USDA APHIS PPQ CPHST Laboratory in Beltsville, Maryland.  The three afore mentioned plant varieties are new hosts records for P. tentaculata.  Several detections of this pathogen have been made in California during the past few years.  Therefore, the current rating for P. tentaculata is reassessed here.

History & Status:

Background: In 1993, Phytophthora tentaculata was first isolated from roots and stems of greenhouse-grown Argyranthemum frutescens (syn. Chrysanthemum frutescens), Leucanthemum vulgare  (syn. C. leucanthemum), Delphinium ajacis, and Verbena sp. in nurseries in the Netherlands and Germany in 1993 (Kröber & Marwitz, 1993).  Later, the pathogen was also reported from Spain (Moralejo et al., 2004; Álvarez et al., 2006), Italy (Cristinzio et al., 2006; Martini et al., 2009) and China (Meng & Wang, 2006; Wang and Zhao, 2014) after detection in nursery-potted and field-grown plants.  In 2012, P. tentaculata was first detected in North America, in sticky monkey flower, Diplacus aurantiacus (syn. Mimulus aurantiacus) growing in a native plant nursery in Monterey County, California.  Plant samples collected by Monterey County and CDFA staff were submitted to CDFA for analysis and the pathogen P. tentaculata was identified by Suzanne Rooney-Latham and Cheryl Blomquist, CDFA plant pathologists (Rooney-Latham & Blomquist, 2014), and later confirmed by the USDA APHIS National Identification Services. The source of the Diplacus (Mimulus) plants was traced back to plants that were grown from seed and cuttings from a historical site in Monterey County.  No Diplacus (Mimulus) plants had been shipped from the native plant nursery prior to the initial detection.  Consequently, all positive Diplacus (Mimulus) plants and materials were destroyed.  The California detection marked the first detection on a native host, albeit in a native plant restoration nursery and a host that has a wide geographical native range in California.  Since its initial Monterey County find, P. tentaculata has also been detected in native plant nurseries in Placer, Butte, Santa Cruz, San Mateo, Orange, and Santa Clara Counties, and in out-planted nursery stock in habitat restoration sites in Alameda, Monterey, and Santa Clara Counties. The pathogen was detected and reported from several new hosts that are listed below (see ‘Hosts’) and include Artemisia douglasiana, A. californica, A. dranunculus, A. palmeri, Diplacus x “Apricot”, Diplacus x “Red brick”, Monardella villosa, and Salvia sp.  Several of these detections were made during a 2014-2015 survey of California native plant nurseries and restoration sites conducted by the collaborative efforts of CDFA, USDA and a private research company.  The survey resulted in the detection of P. tentaculata in 8 out of 16 counties.  The origin of P. tentaculata is unknown.  Presently in California, Phytophthora tentaculata has only been detected in nursery-grown plants that were out-planted in the environment.  The pathogen has persisted on those plants in the field for at least 4.5 years. Therefore, it is likely that in California, the pathway of pathogen spread is from infected nurseries to restoration field sites, and that the pathogen has been spread between and within nurseries by the use of infested pots and plants (Rooney-Latham, et al., 2015).

Hosts: The currently known hosts are included in the plant families Asteraceae, Lamiaceae, Phrymaceae,  Ranunculaceae, Rhamnaceae, Rosaceae, and Verbenaceae.  The host range includes the following plants, diseases and geographical locations:

Apium graveolens (celery); stem and root rot; China (Wang & Zhao, 2014).

Argyranthemum frutescens (syn. Chrysanthemum frutescens) (marguerite daisy); root and stem base rot; Germany & the Netherlands; Root, collar & stalk rot (Kröber & Marwitz 1993).

Artemisia douglasiana (California mugwort); root rot; California, USA (Rooney-Latham, et al., 2015).

Artemisia dracunculus (tarragon); root rot; California, USA (Rooney-Latham et al., 2015). Artemisia californica (California sagebrush); root rot; California, USA (Rooney-Latham et al., 2015).

Artemesia palmeri (Palmer sagewort); root rot; California, USA (see “Initiating Event”).

Aucklandia lappa (rhizomatous medicinal herb); China; stalk rot & wilt (Meng & Wang 2008).

Calendula arvensis (field marigold) (Li et al., 2011).

Ceanothus cuneatus (buckbrush); root rot; California, USA (Rooney-Latham et al., 2015).

Cichorium intybus (chicory, endive); Italy; collar and root rot (Garibaldi et al. 2006).

Delphinium ajacis (nursery stock); Germany & the Netherlands; root, collar & stalk rot (Kröber & Marwitz 1993).

Diplacus aurantiacus (syn Mimulus aurantiacus) (sticky monkey-flower); California, USA.  root and collar rot (Rooney-Latham & Blomquist, 2014).

Diplacus x “Apricot” (Diplacus hybrid variety); root and collar rot; California, USA (see “Initiating Event”).

Diplacus x “Red brick” (Diplacus hybrid variety); root and collar rot; California, USA (see “Initiating Event”).

Frangula californica (syn. Rhamnus californica) (coffeeberry); California; root and collar rot (Frankel et al., 2015; NPAG, 2014).

Gerbera jamesonii (African daisy); Italy; Crown & stem rot (Cristinzio et al. 2006).

Heteromeles arbutifolia (toyon) California, USA (Frankel et al., 2015; NPAG, 2014).

Leucanthemum vulgare (syn. Chrysanthemum leucanthemum) Germany & the Netherlands; Root, collar & stalk rot (Kröber & Marwitz 1993).

Monardella villosa (coyote mint); California, USA (Rooney-Latham et al., 2015).

Origanum vulgare (oregano); Italy.  Leaf russeting & chlorosis, wilt, defoliation, twig dieback,basal stem rot, root rot, entire plant collapse (Martini et al. 2009).

Salvia spp. (sage) California, USA (Frankel et al., 2015; NPAG, 2014).

Santolina chamaecyparissus (lavender cotton); Spain; Root rot (Alvarez et al. 2004).

Verbena sp. (nursery stock); Germany, Netherlands; nursery potted plant in Spain; root, collar & stalk rot (Moralejo et al. 2004).

Symptoms:  Depending on the host species, Phytophthora tentaculata causes moderate to severe root and crown rot, and death in highly infected plants. The symptoms are not unique to P. tentaculata by similar to infections caused by other Phytophthora species, root and stem pathogens and drought.   According to Rooney-Latham et al (2015) symptoms can vary in field-planted nursery stock.  Infected sticky monkey flower plants are stunted, with dull yellowish leaves that turn red as the disease progresses.  Roots and stem collars have necrotic, sunken lesions with few feeder roots and discolored leaves. In some cases, plants may exhibit poor growth and eventually collapse within their first season, while some plants may grow for a year or more before exhibiting severe dieback during hot summers. Transplanted infected Artemisia douglasiana plants did not show dieback, but exhibited stunting and chlorosis more that 4.5 years after being out-planted (Rooney-Latham et al., 2015; Frankel et al., 2015; Kröber & Marwitz 1993).

Damage Potential:  Phytophthora tentaculata causes moderate to severe root and crown rot on woody and semi-woody hosts.  Introduction of P. tentaculata-infected native plants to restoration sites could negatively impact native plants in their natural environment.

Disease Cycle: Generally, species of Phytophthora that cause root and stem rots survive cold winters or hot and dry summers as thick-walled, resting spores (oospores and chlamydospores) or mycelium in infected roots, stems or soil.  During spring, the oospores and chlamydospores germinate to produce motile spores (zoospores) that swim around in soil water and roots of susceptible hosts. The pathogen infects the host at the soil line causing water soaking and darkening of the trunk bark. This infected area enlarges and may encircle the entire stem of small plants which wilt and eventually die.  On large plants, the infected, necrotic area may be on one side of the stem and become a depressed canker below the level of the healthy bark.  Collar rot canker may spread down the root system. Roots are invaded at the crown area or at ground level.   Mycelium and zoospores grow in abundance in cool, wet weather causing damage where the soil is too wet for normal growth of susceptible plants and low temperatures (15-23°C) prevail (Agrios, 2005). Little information is known about the life cycle or biology of Phytophthora tentaculata other than what was provided by the original species description by Kröber and Marwitz. The temperature range of the pathogen is 7°C to 32°C, the optimum temperature being 15°C to 25°C.

Transmission: Like most Phytophthora species, P. tentaculata is soil-borne and water-borne and may be spread to non-infected sites through infected plants, nursery and planting stock, seedlings, soil, run-off and splash irrigation and rain water, and contaminated cultivation equipment and tools.

Worldwide Distribution: Asia: China; Europe: Italy, Germany, the Netherlands, Spain; North America: USA (California).

Official Control: USDA lists Phytophthora tentaculata in the top 5 Phytophthora species of concern and threat to nurseries and forests in Federal New Pest Response Guidelines (USDA APHIS, 2010).  USDA APHIS New Pest Advisory Group determined that P. tentatculata is “actionable and reportable.

California Distribution: Phytophthora tentaculata has been detected in native plant nurseries in Monterey, Placer, Butte, Santa Cruz, San Mateo, Orange, and Santa Clara Counties, and in out-planted nursery stock in habitat restoration sites in Alameda, Monterey, and Santa Clara Counties.

California Interceptions: None.

The risk that Phytophthora tentaculata would pose to California is evaluated below.

Consequences of Introduction:

1) Climate/Host Interaction: Evaluate and score the pest for suitability of 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) – To date, Phytophthora tentaculata has been detected in native plant nurseries in eight counties and in habitat restoration sites (in out-planted nursery stock) in three of those eight counties.  Several native plant hosts are widespread in California.  Since the pathogen is known to attack many plants in the nursery trade, it is possible that the pathogen could appear and survive wherever nurseries, including native plant nurseries, are present in California.  Therefore, there is the potential for this pathogen to establish a widespread distribution in California.

2) Pest Host Range: Evaluate and score the pest as it pertains to host range.  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) – Presently, 23 plant hosts belonging to 7 families have been reported.  Of these, almost half the number of hosts have been reported from California, and are native to the State.  While several new hosts have been reported after the initial detection of the pathogen in Monterey County, based on the present known host range, the risk of the pathogen is evaluated as medium.

3)   Pest Dispersal Potential: Evaluate and score the pest for dispersal potential using these criteria.  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) – Phytophthora tentaculata is soil-borne and water-borne and therefore, primarily spread artificially via infested soils, plants, nursery and planting stock, seedlings, run-off and splash irrigation water, cultivation equipment and tools that may spread contaminated soil and plant materials to non-infected sites.

4) Economic Impact: Evaluate the economic impact of the pest to California using 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 Phytophthora tentaculata could cause severe economic impacts in nursery trade, impacting a number of nursery-produced native and ornamental plants that are commonly used in California landscapes as well as some of which play a significant role in the State’s florist trade.  In addition to lowered crop yields and lowered crop values due to increased need for protective treatments, the management of infestations of a soil- and water-borne pathogen such as Phytophthora spp. in a commercial nursery may be a laborious and expensive problem that would involve alterations in the normal cultural practices such as choice of sites to grow susceptible hosts, and water and growth medium management practices to ensure pathogen propagule-free irrigation water and growth media.

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

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 could significantly impact 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) – The USDA APHIS lists Phytophthora tentaculata in the top 5 Phytophthora species of concern and threat to nurseries and forests in Federal New Pest Response Guidelines (USDA APHIS, 2010).  The presence of P. tentaculata could cause serious impact on native plants, threatened or endangered species, disrupt critical habitats by killing critical species necessary for species diversity and soil stability, necessitate official or private treatment programs to preserve critical, rare, or endangered species, and significantly impact cultural practices, home/urban and/or ornamental plantings.

Consequences of Introduction to California for Phytophthora tentaculata:

Add up the total score and include it here

– Low = 5-8 points

– Medium = 9-12 points

– High = 13-17 points

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

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

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

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

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

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

Evaluation is Medium (-2). To date, Phytophthora tentaculata has been detected in native plant nurseries in Monterey, Placer, Butte, Santa Cruz, San Mateo, Orange, and Santa Clara Counties, and in out-planted nursery stock in habitat restoration sites in Alameda, Monterey, and Santa Clara 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 = 12.

Uncertainties:

While more is known about the presence of Phythophthora tentaculata in California since its original detection in Monterey County, more researched information is needed on the distribution, behavior and threat of Phytophthora tentaculata in California’s natural soils and plant communities under diverse climatic environments.  

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Phytophthora tentaculata remains B.

References:

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

Álvarez, L. A., A. Pérez-Sierra, M. León, J. Armengol, and J. García-Jiménez.  2006.  Lavender cotton root rot: a new host of Phytophthora tentaculata found in Spain. Plant Disease 90:523. http://dx.doi.org/10.1094/pd-90-0523A

Cristinzio, G., I. Camele and C. Marcone.  2006.  Phytophthora tentaculata su gerbera in Italia.  First report of Phytophthora tentaculata on gerbera in Italy.  Informatore Fitopatologico 56:23-25. http://www.cabdirect.org/abstracts/20063066005.html;jsessionid=C23F9F14D93FF641EEE94948EFEB99D5.

Frankel, S., S. Rooney-Latham, C. L. Blomquist, and E. Bernhardt.  2015.  Pest Alert: Phytophthora tentaculata.  Technical Report, February 2015, United States Department of Agriculture. http://www.suddenoakdeath.org/wp-content/uploads/2015/02/P.tentaculata.

Garibaldi A., G. Gilardi, M. L. Gullino.  2010. First report of collar and root rot caused by Phytophthora tentaculata on witloof chicory (Cichorium intybus) in Italy. Plant Disease 94:1504.

Kröber, H., and R. Marwitz.  1993.  Phytophthora tentaculata sp. nov. und Phytophthora cinnamomi var. parvispora var. nov., zwei neue Pilze von Zierpflanzen in Deutschland. Zeitschrift fur Pflanzenkrankheiten und Pflanzenschutz 100, 250-258. [Original Description]

Martini, P., A. Pane, F. Raudino, A. Chimento, S. Scibetta, and S. O. Cacciola.  2009.  First report of Phytophthora tentaculata causing root and stem rot of oregano in Italy. 93:843. http://dx.doi.org/10.1094/PDIS-93-8-0843B.

Meng, J., and Y. C. Wang.  2008.  First Report of Stalk Rot Caused by Phytophthora tentaculata on Aucklandia lappa in China. Plant Disease 92 (9): 1365.

doi:10.1094/PDIS-92-9-1365B. http://apsjournals.apsnet.org/doi/abs/10.1094/PDIS-92-9-1365B.

Moralejo, E., M. Puig, and W. A. Man in’t Veld.  2004.  First report of Phytophthora tentaculata on Verbena sp. in Spain. The British Society for Plant Pathology.

http://www.bspp.org.uk/publications/new-disease-reports/ndr.php?id=009038. May 31, 2009.

USDA APHIS.  2010.  New Pest Response Guidelines: Phytophthora species in the Environment and Nursery Settings. 229 pages.

Rooney-Latham, S., and C. L. Blomquist.  2014. First report of root and stem rot caused by Phytophthora tentaculata on Mimulus aurantiacus in North America. Plant Disease 98(7):996.

Rooney-Latham, S., C. L. Blomquist, T. Swiecki, and E. Bernhardt.  2015.  Phytophthora tentaculata.  Forest Phytophthoras 5(1):  doi:10.5399/osu/fp.5.1.3727.

Schwartzburg, K., H. Hartzog, C. Landry, J. Rogers, and B. Randall-Schadel.  2009. Prioritization of Phytophthora of Concern to the United States. USDA APHIS PPQ CPHST PERAL (Plant Epidemiology and Risk Analysis Laboratory), Raleigh, NC. 61 pages.

Wang, T. and W. Zhao.  2014.  First report of Phytophthora tentaculata causing stem and root rot on celery in China. http://dx.doi.org/10.1094/PDIS-06-13-0592-PDN.

Responsible Party:

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

Comment Format:

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

Example Comment: 

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

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♦  Comments may not be posted if they:

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

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Pest Rating: B

Posted by ls

Plant Pathogens, Viruses and viroids

Freesia Sneak Virus (FreSV)

California Pest Rating forFreesia Sneak Virus
Freesia Sneak Virus
Pest Rating: B
PEST RATING PROFILE
Initiating Event:

None.     

History & Status:

Background:  Freesia sneak virus (FreSV) is associated with freesia leaf necrosis disease. The disease has been reported in Europe since the 1970s.  Although FreSV has been most closely correlated with freesia leaf necrosis symptoms in freesia plants, other species within the same genus may also be correlated (e.g., Freesia mosaic virus FreMV) and, therefore, the causal agent(s) is/are still being determined (Bouwen, 1994; Meekes & Verbeek, 2011).

Freesia sneak virus is a plant virus belonging to the genus Ophiovirus in the family Ophioviridae.  Freesia sneak virus is soil-borne and vectored by the soil-borne fungus, Olpidium brassicae. Initially, the virus was provisionally called Freesia Ophiovirus, but is now known as Freesia sneak virus (Vaira et al., 2006).

In the USA, Freesia sneak virus was first reported from infected Freesia spp. in Virginia in 2009 (Vaira et al., 2009).  The pathogen was detected in California, in symptomatic freesia plant samples collected during April 2014, from a nursery in San Luis Obispo County. The pathogen was identified by Tongyan Tian, CDFA plant pathologist.  Subsequently, all infected plant material was destroyed.

Hosts: Freesia spp. (Iradaceae) and Lachenalia spp. (Hyacinthaceae) (Jeong, et al., 2014; Meekes & Verbeek, 2011; Vaira et al., 2007, 2009).  Both hosts are monocots native to South Africa.

Symptoms: Symptoms may be affected by environmental conditions (Vaira et al., 2006).

Freesia leaf necrosis disease mainly affects the leaves exhibiting chlorotic spots and stripes that start at the leaf tip and usually spread over the entire leaf.  Later these chlorotic spots turn grey-brown and become necrotic.  Mildly infected plants show light chlorotic symptoms only on the lower leaves.  Flowers and corms do not seem to be affected by the disease (Van Dorst, 1973; Bouwen, 1994; Meekes & Verbeek, 2011).

Damage Potential: In detection surveys conducted in Korea, Freesia sneak virus was detected from 71.7% of 138 plants tested (Jeong et al., 2014).  Infection rates of 10-25% percent of plants shipped to the USA have been reported (Hansen, 2008; Vaira et al., 2009).  In California, nursery and private productions of freesia and lachenalia plants, in particular, may be impacted if infected with Freesia sneak virus.

Transmission: in nature, Freesia sneak virus is vectored by the soil-borne fungus, Olpidium brassicae, and not by mechanical transmission.  Resting spores of O. brassicae are very persistent and can survive for more than twenty years in soil without losing the capacity to transmit the disease (Meekes & Verbeek, 2011).   Therefore, spread of FreSV is also through movement of contaminated soils and plants.

Worldwide Distribution:  Asia: Korea; Africa: South Africa; Europe: Northern Europe including the Netherlands, Italy; North America: USA (Virginia) (Jeong et al., 2014; Meekes & Verbeek, 2011; Vaira, et al., 2007, 2009).

Official Control: None reported.

California Distribution: San Luis Obispo (nursery).

California Interceptions: There have not been any interceptions of Freesia sneak virus-infected plants entering California.

The risk Freesia sneak virus would pose to California is evaluated below.

Consequences of Introduction: 

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

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

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

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

Risk is Medium (2) – Freesia sneak virus is likely to establish wherever freesia and lachenalia plants are grown in limited areas of California. Freesia has limited production in state and is naturalized mostly in the north coast region, as well as cultivated in nursery and private production sites – including home gardens.    Lachenalia is grown mainly in nurseries and in private productions as a hobbyist’s plant.   

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) – Freesia sneak virus is limited to Freesia spp. (Iradaceae) and Lachnenalia spp. (Hyacinthaceae).

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

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

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

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

Risk is Medium (2) – Freesia sneak virus has high reproductive potential.  In nature, its spread to non-infected plants is dependent on the presence of the soil-borne fungus vector, Olpidium brassicae.  Resting spores of O. brassicae are very persistent and can survive for more than twenty years in soil without losing their viability. Therefore, FreSV is also spread through movement of contaminated soils and plants.  The pathogen is not mechanically transmitted.

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) – Incidents of Freesia sneak virus infections could lower plant value resulting in loss in market sales of nursery-grown freesia and lachenalia plants.  The pathogen is vectored by the soil fungus, Olpidium brassicae.    

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) – Plant infections caused by Freesia sneak virus are likely to have a minimal impact on the overall environment but may significantly impact home gardening and ornamental plantings.

Consequences of Introduction to California for Freesia sneak virus

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

-Low = 5-8 points

–Medium = 9-12 points

-High = 13-15 points

Total points obtained on evaluation of consequences of introduction of Freesia sneak virus to California = 9.

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.  Freesia sneak virus-infected freesia plants have only been detected in a contained nursery environment in California.  Those plants were subsequently destroyed and therefore, the pathogen is not considered established in the State.

Final Score:

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

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

Uncertainty:

None.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Freesia sneak virus is B.

References:

Bouwen, I.  1994.  Freesia leaf necrosis: some of its mysteries revealed.  Virus Diseases of Ornamental Plants VIII, Acta Horticulturae 377: 311-318.

Hansen, M. A.   2008.  Freesia sneak virus – a new find for the United States.  Virginia Cooperative Extension, Virginia Tech Plant Disease Clinic: https://www.cals.ncsu.edu/plantpath/activities/societies/ornamental/2008_talks/freesia_sneak_virus_4.pdf.

Jeong, M. I., Y. J. Choi, J. H. Joa, K. S. Choi, and B. N. Chung.  2014.  First report of Freesia sneak virus in commercial Freesia hybrida cultivars in Korea.  Plant Disease 95:162. http://dx.doi.org/10.1094/PDIS-05-13-0484-PDN.

Meekes, E. T. M., and M. Verbeek.  2011.  New insights in Freesia leaf necrosis disease.  Proceedings XIIth IS on Virus Diseases of Ornamental Plants; Editors A. F. L. M. Derks et al.  Acta Horticulturae  901, ISHA 2011.

Vaira, A. M., V. Lisa, A. Costantini, V. Masenga, S. Rapetti, and R. G. Milne.  2006.  Ophioviruses infecting ornamentals and a probable new species associated with a severe disease in Freesia.  Proceeding XIth IS on Virus Diseases in Ornamentals, Ed. C. A. Chang.  Acta Horticulturae 722, ISHA 2006.

Vaira, A. M., R. Kleynhans, and J. Hammond.  2007.  First report of Freesia sneak virus infecting Lachenalia cultivars in South Africa.  Plant Disease 91:770.  http://dx.doi.org/10.1094/PDIS-91-6-0770A.

Vaira, A. M. , M. A. Hansen, C. Murphy, M. D. Reinsel, and J. Hammond.  2009.  First report of Freesia sneak virus in Freesia sp. in Virginia.  Plant disease, 93:965. http://dx.doi.org/10.1094/PDIS-93-9-0965B.

Van Dorst, H. J. M.  1973. Two new disorders in freesias.  Netherland Journal of Plant Pathology 79:130-137.

Responsible Party:

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

Comment Format:

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

Example Comment: 

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

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

♦  Comments may not be posted if they:

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

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

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

Violates agency regulations prohibiting workplace violence, including threats.

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

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

Pest Rating: B

Posted by ls

Fungi, Plant Pathogens

Greeneria uvicola (Berk. & M. A. Curtis) Punith. 1974

California Pest Rating Proposal for
Greeneria uvicola (Berk. & M. A. Curtis) Punith. 1974
Pest Rating: B
PEST RATING PROFILE
Initiating Event:  

On December 16, 2015, a shipment of grape leaves from Texas, destined to a retail store in California, was intercepted by the Los Angeles County officials.  The leaves had symptoms of leaf spots and a sample was collected and sent to the CDFA Plant Pathology Laboratory for disease diagnosis.  The fungal pathogen, Greeneria uvicola, was identified as the cause for the leaf spots, by Suzanne Rooney Latham, CDFA plant pathologist.  The pathogen was given a Q rating and subsequently the shipment of grape leaves was destroyed.  The risk of infestation of Greeneria uvicola in California is evaluated and a permanent rating is herein proposed. 

History & Status:

Background:  Greeneria uvicola is the cause of ‘Bitter Rot’ of grapes. The disease is cosmopolitan and common in the southern eastern United States, while being an occasional problem in the northern region as far as Long Island and New England states.  Greeneria uvicola is an asexually reproducing fungus with no known sexual state. Taxonomically, the pathogen is also known by several synonyms (including, Greenaria fuliginea, Melanconium fuligineum, and Phoma uvicola) and based on molecular data was placed in Ascomycetes, Diaporthales (Farr et al., 2001; Sutton, 2015).

Hosts: Grapevine (Vitis spp.).

Symptoms:  The pathogen infects all above ground vegetative plant parts including stem, leaves, tendrils and fruits.  Leaf symptoms, which are more common on muscadine grapes than on bunch grapes, appear as tiny, sunken, reddish-brown flecks with yellow halos.  Stem and petiole infects result in round to elliptical, reddish brown to black lesions which may be slightly raised or sunken.  Flecking of sepals and blighting of flower buds may also occur.  The fungus initially invades the berry from the berry stem (pedicel) at the onset of ripening. Infected light-skinned berries turn brown and form multiple, prominent fungal asexual fruiting bodies (acervuli) once the berries reach their full size.  As the rot progresses through the infected berries, the acervuli form in concentric rings, but are more uniformly distributed once the fruit is completely rotted.  These symptoms are less visible on dark-skinned berries which rough-skinned and iridescent.  Eventually, infected berries soften, shrivel, may be completely covered with acervuli, and may abscise or become mummified and remain attached (Sutton, 2015).

Damage Potential:  Infected fruit becomes rotted and as rotted fruit begins to soften they have a distinct bitter taste which is carried through the winemaking process resulting in a finished wine with an unpleasant, burnt or bitter taste.  Therefore, the marketability of diseased fruit for table or wine use is reduced.

Disease Cycle: The pathogen overwinters as a saprophyte on fallen fruit, cold-damaged shoot tips, and necrotic bark of the trunk and cordons.  In spring, gelatinous masses of spores (conidia) are produced from acervuli and washed by rain to green vegetative parts including the pedicels.  Disease development requires long and warm rains in spring, followed by warm, humid summers.  Infections occur during wet periods at 12-30°C, and optimally at 22.4-24.6°C, with 6-12 hrs wetness.  The fungus invades the pedicel and remains latent until fruit mature.  At that time the pathogen actively grows from the infected pedicel into the maturing fruit resulting in berry rot.  Conidia are produced in infected berries and rain splashed onto other ripening fruit causing secondary infections.  Infections usually occur in fruit wounded by insects, birds, hail, heavy rainstorms, or mechanically.  Berries are most susceptible at the onset of ripening however they may be infected by conidia anytime between bloom and harvest (Sutton, 2015).

Transmission:   The pathogen is spread through infected above ground vegetative plant materials and dead plant debris (leaves, stems, tendrils, and mummied fruits), rain/water splash.

Worldwide Distribution: Greeneria uvicola is distributed worldwide and reported from Asia: India, China, Taiwan, Thailand; Africa: South Africa; Europe: Bulgaria, Poland, Ukraine; North America: USA, Mexico; South America: Brazil, Costa Rica; Uruguay; Australia (Farr & Rossman, 2016; Samuelian, et al., 2013; ChaoYu et al., 2015).  Greece, Japan, and New Zealand have also been reported (Sutton, 2015).

In the USA, Greeneria uvicola has been reported mainly from the south eastern states.  Its distribution includes Florida, Georgia, Missouri, Mississippi, Ohio, Oklahoma, North Carolina, South Carolina, and West Virginia (Farr & Rossman, 2016).

Official Control:  Greeneria uvicola is on the ‘Harmful Organism List’ for China (PCIT, 2015).  Presently, G. uvicola has a temporary (Q) rating as a quarantine, actionable pathogen by the CDFA.

California Distribution:  Greeneria uvicola is not reported from California.

California Interceptions: There has been only one interception of Greeneria uvicola-infected grape leaves in California (see ‘Initiating Event”).

The risk Greeneria uvicola 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) – The requirements for a suitable climate of long periods of warm rains in spring, followed by warm, humid summers would not likely favor or greatly limit the establishment of Greenaria uvicola in California where grape is usually cultivated under warm and dry 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) – Grape (Vitis spp.) is the only host.  Although the host range is very limited, in California grape is a major crop that is cultivated over significant acreage.

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

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

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

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

Risk is Medium (2) – Greeneria uvicola is highly reproductive, producing gelatinous masses of conidia for primary and secondary infections.  Dispersal of conidia is dependent on rain splash for delivery to, and infection of non-infected above ground parts of the grapevine.

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) – Bitter rot diseased fruit is rotted and has a bitter taste that results in finished wine with an unpleasant bitter or burnt flavor.  Therefore, Greeneria uvicola-infected fruit could lower crop yield of healthy fruit bunches, lower crop value, and trigger loss of markets of table and wine grapes.   

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 gardens cultivated with table and/or wine grapes could be significantly impacted if infected with the bitter rot pathogen.

Consequences of Introduction to California for Greeneria uvicola:

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 Greeneria uvicola to California = 9

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 = 9.

Uncertainty:

None.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for the bitter rot pathogen, Greeneria uvicola is B .  

References:

ChaoYu, Cui, Jiang JunXi, Ouyang Hui, Li Cheng, Liu DengQuan, and Huang Ting.  2015.  First report of Greeneria uvicola causing bitter rot of grape in China.  Journal of Phytopathology, 163:780-782.

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 January 12, 2016, from http://nt.ars-grin.gov/fungaldatabases/

Farr. D. F., L. A. Castlebury, A. Rossman, and O. Erincik.  2001.  Greeneria uvicola, cause of bitter rot of grapes, belongs in Diaporthales.  Sydowia-Horn, 53:185-199.

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

Samuelian, S. K., L. A. Greer, K. Cowan, M. Priest, T. B. Sutton, S. Savocchia, and C. C. Steel.  2013.  Phylogenetic relationships, pathogenicity and fungicide sensitivity of Greeneria uvicola isolates from Vitis vinifera and Muscadinia rotundifolia.  Plant Pathology, 62: 829-841.

Sutton, T. B.  2015.  Diseases caused by biotic factors, diseases caused by fungi and Oomycetes: Bitter Rot.  Compendium of Grape Disease, Second Edition.APS Press, The American Phytopathological Society, pg. 24-26.

Responsible Party:

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

Comment Format:

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

Example Comment: 

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

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♦  Comments may not be posted if they:

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Pest Rating: B

Posted by ls

Fungi, Plant Pathogens

Colletotrichum cordylinicola Phoulivong, L. Cai & K. D. Hyde, 2011

California Pest Rating Proposal for
Colletotrichum cordylinicola Phoulivong, L. Cai & K. D. Hyde, 2011
Pest Rating: B
PEST RATING PROFILE
Initiating Event:  

On October 6, 2015 a shipment of Green Ti plant cuttings (Cordyline glauca) showing leaf blight symptoms and destined to a nursery in San Diego County, was intercepted and sampled by San Diego County Agricultural officials.   The shipment had originated in Costa Rica.  Diseased plant samples were sent to the CDFA Plant Diagnostics Branch for diagnosis.  Suzanne Latham, CDFA plant pathologist identified the leaf spot and anthracnose pathogen, Colletotrichum sp. as the cause for the disease. The identity of the associated pathogen was later confirmed to be C. cordylinicola by USDA National Identification Services at Beltsville, Maryland, and marked the first detection of C. cordylinicola in continental USA.  The pathogen was assigned a temporary Q rating by the CDFA and consequently, all infected plant materials were destroyed. The risk of infestation of C. cordylinicola in California is evaluated and a permanent rating is proposed.

History & Status:

Background:  In 2010, Phoulivong et al. first reported the fungal species, Colletotrichum cordylinicola causing anthracnose disease in Cordyline fruticosa in Thailand and Eugenia javanica in Laos. They noted that the isolate from C. fruticosa was not pathogenic to E. javanica and vice versa, and that both strains may represent different pathotypes.  However, Weir et al. (2012), through further molecular analysis placed both isolates within the same species.  Colletotrichum cordylinicola is a distinct fungus species belonging to the vastly morphological and physiological variable C. gloeosporioides and is genetically identified from other species of the complex (Weir et al, 2012). Colletotrichum cordylinicola has not been reported from the USA.  A reported identification of C. cordylinicola detected on Cordyline fruticosa in Florida (Sharma et al., 2014) is considered inconclusive by the USDA APHIS PPQ National Identification Services.

Hosts: Cordyline (Cordyline fruticosa) in the Asparagaceae family, and wax jambu (Eugenia javanica = syn. Syzygium samarangense) in the Myrtaceae family.

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

Damage Potential:  In general, anthracnose disease of fruits and leaves caused by Colletotrichum spp., can result in reduction in yield quantity and quality of agricultural crops and fruit trees (Phoulivong et al., 2010).  It is, therefore, highly likely that Colletotrichum cordylinicola can result in reduced plant quality and growth, fruit production and marketability.  Estimates of yield/crop loss due to this pathogen have not been reported.  Nursery productions of ornamental cordyline and wax jambu plants are particularly at risk as nursery conditions are often conducive to infection by Colletotrichum species.  In open fields, disease development may be sporadic as it is affected by levels of pathogen inoculum and environmental conditions.

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

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

Worldwide Distribution:  Colletotrichum cylindricola is distributed in Thailand, Laos, and New Zealand (Farr & Rossman, 2015; Phoulivong et al., 2010; Weir et al., 2012).

Official Control:  Presently, in California C. cordylinicola is an actionable, Q-rated pathogen, and infected plant material is subject to destruction or rejection.  The pathogen is categorized as ‘reportable’ by the USDA.

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

California Interceptions: There has been one reported interception of Colletotrichum cordylinicola-infected Cordyline glauca plant cuttings. (see ‘Initiating event’).

The risk Colletotrichum cordylinicola 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) – Similar to other species of Colletotrichum cordylinicola requires humid, wet, rainy weather for conidia to infect host plants. The environmental requirements and narrow host range may limit the ability of the pathogen to fully establish and spread under outdoor dry conditions in the State.

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

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

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

Risk is Low (1) – Colletotrichum cylindricola has a limited host range comprising of cordyline (Cordyline fruticosa) and wax jambu (Eugenia javanica) .  Cordyline is an indoor decorative plant that is commonly produced in nursery greenhouses in California. Outdoor cultivation of this plant is not common.  Wax Jambu (Eugenia javanica) may be grown in limited residential and commercial public regions in Southern California..

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

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

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

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

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

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

A.  The pest could lower crop yield.

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

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

D.  The pest could negatively change normal cultural practices.

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

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

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

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

– Medium (2) causes 2 of these impacts.

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

Risk is Medium (2) –Anthracnose-infected cordyline and wax jambu plants may result in lower crop value and market loss.  .Nursery production of these hosts is particularly at risk as nursery conditions are often conducive to infection by Colletotrichum species.  Its economic impact is evaluated as a medium risk.   

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

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

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

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

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

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

Score the pest for Environmental Impact. Score:

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

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

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

 Risk is Medium (2) – The pathogen could significantly impact home/urban gardens and ornamental plantings.

Consequences of Introduction to California for Colletotrichum cordylinicola:

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 cordylinicola to California = (9).

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 cordylinicola is not established in California. 

Final Score:

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

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

Uncertainty:

None.

Conclusion and Rating Justification:

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

References:

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

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

Phoulivong S., L. Cai, N. Parinn, H. Chen, K. A. Abd-Elsalam, E. Chukeatirote, and K. D. Hyde.  2010.  A new species of Colletotrichum from Cordyline fruticosa and Eugenia javanica causing anthracnose disease.  Mycotaxon 114:247-257.

Sharma K., E. Goss, and Ariena H. C. van Bruggen.  2014.  Isolation and identification of the fungus Colletotrichum cordylinicola causing anthracnose disease on Cordyline fruticosa in Florida.  HortScience 49:911-916.

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

Responsible Party:

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

Comment Format:

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

Example Comment: 

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

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

♦  Comments may not be posted if they:

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

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

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

Violates agency regulations prohibiting workplace violence, including threats.

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

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

Pest Rating: B

Posted by ls

Plant Pathogens, Viruses and viroids

Grapevine Red Blotch associated Virus (GRBaV)

California Pest Rating for
Grapevine Red Blotch associated Virus (GRBaV)
Pest Rating:  B
PEST RATING PROFILE
Initiating Event:

None.

History & Status:

Background: The origin of Grapevine red blotch does not appear to be recent.  For long the disease escaped the attention of vineyard growers because of its close resemblance to leafroll disease symptoms. Nevertheless, in 2008, an emerging grapevine disease – later termed red blotch disease, was first recognized in a Cabernet Sauvignon vineyard in Napa Valley, California. The disease was typified by leaf reddening and delayed fruit maturity in red cultivars of grapevine and initially confused with grapevine leafroll due to the late-season symptom of leaf reddening.  However, some symptomatic leafroll grapevine cultivars were found to be free of leafroll viruses and DNA sequencing analysis revealed the presence of a single stranded DNA virus that was named, Grapevine red blotch associated virus (Al Rwahnih et al., 2012, 2013).  In 2010, severe decline of grapevine cultivar ‘Cabernet franc’ was discovered in a vineyard in New York.  As in California, the disease was initially described as leafroll but following nucleic acid analysis, was found to be free of leafroll viruses, and found to have a single stranded DNA that, on sequence analysis, resembled members of the virus family Geminiviridae.  This virus was tentatively named, Grapevine cabernet franc-associated virus (GCFaV).  Subsequently, both GRBaV and GCFaV were found to be the same virus and the name, Grapevine red blotch associated virus was used for the causal organism of the associated grapevine red blotch disease to distinguish the symptoms from those caused by leafroll viruses and other graft-transmissible agents (Krenz et al., 2014).  Grapevine red blotch associated virus is a newly identified virus of grapevines and a putative member of a new genus within the family Geminiviridae (Sudarshana et al., 2015).  In 2013, in Washington State vineyards, a disease similar to grapevine red blotch was reported to be caused by Grapevine red leaf-associated virus, which was determined to be genetically identical to GRBaV (Poojari et al., 2013).

Since its initial discovery in 2008, GRBaV has been detected in several regions of California (see ‘California Distribution’).  Furthermore, through surveys, the disease was found to be widely distributed in North America.  Grapevine red blotch has not been reported outside of North America. Studies conducted in the National Clonal Germplasm Repository (NCGR) located near Winters, California, revealed that grapevine accessions originating from 33 countries and five continents outside North America tested positive for the virus.  However, it was not concluded from those studies that the virus occurs in those countries (Rwahnih et al., 2015).

Hosts: Vitis vinifera (grapevine) red cultivars: Cabernet Franc, Cabernet Sauvignon, Malbec, Merlot, Mourvèdre, Petite Sirah, Petit Verdot, Pinot Noir, and Zinfandel; white V. vinifera cultivars such as Chardonnay, Riesling, Semillon, and Viognier; also, table and raisin grapes and some root stocks.  GRBaV has been detected in grapevine collections, nursery stock and established vineyards (EPPO, 2015).

Symptoms: Symptoms have been observed in grapevines of various ages in young (first leaf) and mature (5-20 yr old vineyards. Generally, symptoms appear in late August through September as red blotches on leaf blades on basal portions of shoots either between secondary or tertiary veins or extending from the leaf margin with the veins turning partly or fully red (Sudarshana & Fuchs, 2015). Foliar symptoms in white cultivars are less conspicuous and usually involve irregular chlorotic areas that may become necrotic late in season (Sudarshana et al., 2015).  Certain white cultivars, such as Sauvignon Blanc may remain asymptomatic (EPPO, 2015).  Symptoms of red blotch are very similar to those caused by leafroll disease in that leaves, primarily at the base of shoots, turn red during early fall.  However, unlike leafroll, red blotch affected leaves have pink or red veins on the underside of leaves without the margins rolling downwards.

Damage Potential:  GRBaV reduces fruit quality and ripening of grape.  The most significant impact of red blotch disease is the reduction of sugar levels (°Brix), up to 4-5 times lower, in fruit of diseased grapes than in fruit of healthy grapes thereby, causing delayed harvests.  This is of particular concern to wine grape growers who must achieve a certain sugar level in their wine grapes before the latter are acceptable for wine production.  Also, fruit of diseased grapevines have increased acidity. The effect of red blotch disease on fruit yield or vine longevity is not known.

Transmission:  GRBaV is graft transmissible.  The primary source of spread of the pathogen is through infected planting material.  There is no evidence for seed transmission (similar to other members of Geminiviridae).  While the role of an insect vector in transmitting GRBaV in vineyards has not been confirmed, greenhouse experiments have shown that the Virginia creeper leafhopper (Erythroneura aicazc) is involved in spreading the virus from vine to vine in the greenhouse.  The role of this leafhopper in vineyards and how plant-to-plant spread of GRBaV occurs under field conditions are not yet known (Rwahnih et al., 2015; Sudarshana & Fuchs, 2015).

Worldwide Distribution: North America: USA (Arizona, Arkansas, California, Georgia, Idaho, Maryland, New Jersey, New York, North Carolina, Oregon, Pennsylvania, Texas, Virginia, and Washington) and Canada (British Columbia and Ontario) (EPPO, 2015; McFadden-Smith, 2013; Sudarshana & Fuchs, 2015).

Official Control: Grapevine red blotch associated virus is on the “2015 Alert list” of the European and Mediterranean Plant Protection Organization (EPPO, 2015).  Currently, it is a Q-rated quarantine pathogen in California.

California Distribution:  Red blotch disease has been found in Napa and Sonoma Counties, as well as in the central coast (San Luis Obispo County) and San Joaquin Valley (Fresno County) regions of the State (Al Rwahnih et al., 2013; Sudarshana & Fuchs, 2015).

California Interceptions: There are no records of detection of GRBaV in quarantine shipments of plant material intercepted in California.

The risk Grapevine red blotch associated virus would pose to California is evaluated below.

Consequences of Introduction: 

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

– Low (1) Not likely to establish in California; or likely to establish in very limited areas.
– Medium (2) may be able to establish in a larger but limited part of California.
– High (3) likely to establish a widespread distribution in California.

Risk is High (3) –.Grapevine red blotch associated virus has already spread to certain grape growing counties in California’s northern, central and San Joaquin Valley regions.  If left unchecked, the pathogen is likely to establish a widespread distribution in grape producing regions of the State.

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) – Grapevine red blotch associated virus has been identified in nine Vitis vinifera red cultivars: Cabernet Franc, Cabernet Sauvignon, Malbec, Merlot, Mourvèdre, Petite Sirah, Petit Verdot, Pinot Noir, and Zinfandel; and white cultivars V. vinifera cultivars such as Chardonnay, Riesling, Semillon, and Viognier; also, table and raisin grapes and some root stocks. Although the pathogen has a limited host range, Grape production is a major enterprise and grapevine is cultivated over significant acreage 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) – Grapevine red blotch associated virus is graft transmissible.  The primary source of spread of the pathogen to vineyards is through infected planting material. The role of an insect vector in vineyards and plant-to-plant spread of GRBaV under field conditions are not yet known.

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

A.  The pest could lower crop yield.

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

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

D.  The pest could negatively change normal cultural practices.

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

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

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

– Low (1) causes 0 or 1 of these impacts.
– Medium (2) causes 2 of these impacts.
– High (3) causes 3 or more of these impacts.

Risk is Medium (2) – The effect of red blotch disease on fruit yield or vine longevity is not known. However, Grapevine red blotch associated virus reduces fruit quality and ripening of grape resulting in lowered crop value, loss of markets and is likely to negatively change normal cultural practices including removal of diseased vines and replant of vineyards since there is no cure once the virus is present in a vineyard (UCDavis News & information, 2013).  The most significant impact of red blotch disease is the reduction of sugar levels (°Brix), up to 4-5 times lower, in fruit of diseased grapes than in fruit of healthy grapes thereby, causing delayed harvests.  This is of particular concern to wine grape growers who must achieve a certain sugar level in their wine grapes before the latter are acceptable for wine production.  Also, fruit of diseased grapevines have increased acidity. The involvement of an insect vector in spreading the virus under field conditions is not known.

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) – Grapevine red blotch associated virus could significantly impact cultural practices, home/urban plantings of disease infected grapevines and trigger official or private treatment programs.

Consequences of Introduction to California for Grapevine red blotch associated virus

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

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

Total points obtained on evaluation of consequences of introduction of GRBaV to California = Medium (11).

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

-Not established (0) Pest never detected in California, or known only from incursions.
-Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).
–Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.
-High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

Evaluation is Medium (-2). Presently, Grapevine red blotch associated virus has been reported from Napa and Sonoma Counties, as well as in the central coast (San Luis Obispo County) and San Joaquin Valley (Fresno County) regions 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 = 9.

Uncertainty: 

The means by which GRBaV spreads in vineyards is not known and is a current focused study of  researchers.  Virus spread is suspected via a vector but this has yet to be identified. Knowledge gained in this area may further the distribution of the virus than what is reported here.     

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Grapevine red blotch associated virus is B.

References:

Al Rwahnih, M., A. Dave, M. Anderson, J. K. Uyemoto, and M. R. Sudarshana.  2012.  Association of a circular DNA virus in grapevine affected by red blotch disease in California.  Proceedings of the 17th Congress of ICVG, Davis, California, USA. October 7-14, 2012.

Al Rwahnih, M., M. R. Sudarshana, and J. Wolpert.  2013. Red Blotch Disease.  Viticulture Information, University of California Integrated Viticulture: http://iv.ucdavis.edu/Viticultural_Information/?uid=284&ds=351.

Al Rwahnih, M., A. Dave, M. M. Anderson, A. Rowhani, J. K. Uyemoto, and M. R. Sudarshana.    2013.  Association of a DNA virus with grapevines affected by red blotch disease in California.  Phytopathology 103:1069-1076.

Al Rwahnih, A. Rowhani, D. A. Golino, C. M. Islas, J. E. Preece, and M A. Sudarshana.  2015.  Detection and genetic diversity of Grapevine red blotch-associated virus isolated in table grape accessions in the National Clonal Germplasm Repository in California.  Canadian Journal of Plant Pathology, 37:130-135. http://dx.doi.org/10.1080/07060661.2014.999705.

EPPO.  2015.  Grapevine red blotch-associated virus.  European and Mediterranean Plant Protection Organization: http://www.eppo.int/QUARANTINE/Alert_List/viruses/GRBAV0.htm.

Krenz, B., J. R. Thompson, H. L. McLane, M. Fuchs, and K. L. Perry.  2014.  Grapevine red blotch-associated virus is widespread in the United States.  Phytopathology 104:1232-1240.

McFadden-Smith, W.  2013.  Grapevine red blotch associated virus: A newly identified disease in vineyards.  Ontario Ministry of Agriculture, Food and Rural Affairs: http://www.omafra.gov.on.ca/english/crops/hort/news/hortmatt/2013/22hrt13a1.htm.

Poojari S, O. J. Alabi, V. Y. Fofanov, and R. A. Naidu RA. 2013. A leafhopper transmissible DNA virus with novel evolutionary lineage in the family Geminiviridae implicated in grapevine redleaf disease by next-generation sequencing. PLoS One. 8:e64194. doi:10.1371/journal.pone.0064194.

Sudarshana M., and M. Fuchs.  2015.  Grapevine Red Blotch.  In Compendium of Grape Diseases, Disorders, and Pests, Second Edition, Edited by W. F. Wilcox, W. D. Gubler, and J. K. Uyemoto. The American Phytopathological Society, St. Paul, Minnesota. 122-123 pp.

Sudarshana, M. R., K. L. Perry, and M. F. Fuchs.  2015.  Grapevine red blotch associated virus, an emerging threat to the grapevine industry.  Phytopathology, 105:1026-1032.  http://dx.doi.org/10.1094/PHYTO-12-14-0369-FI.

UCDavis News and Information.  2015.  New technology offers hope for solving grapevine red blotch disease problem.  http://news.ucdavis.edu/search/news_detail.lasso?id=10499.

Responsible Party:

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

Comment Format:

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

Example Comment: 

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

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

♦  Comments may not be posted if they:

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

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

Pest Rating: B

Posted by ls

Fungi, Plant Pathogens

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

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

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

History & Status:

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

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

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

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

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

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

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

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

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

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

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

Consequences of Introduction: 

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

– Low (1) Not likely to establish in California; or likely to establish in very limited areas.
– Medium (2) may be able to establish in a larger but limited part of California.
– High (3) likely to establish a widespread distribution in California.

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

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

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

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

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

– Low (1) does not have high reproductive or dispersal potential.
– Medium (2) has either high reproductive or dispersal potential.
– High (3) has both high reproduction and dispersal potential.

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

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

A.  The pest could lower crop yield.
B.  The pest could lower crop value (includes increasing crop production costs).
C.  The pest could trigger the loss of markets (includes quarantines).
D.  The pest could negatively change normal cultural practices.
E.  The pest can vector, or is vectored, by another pestiferous organism.
F.  The organism is injurious or poisonous to agriculturally important animals.
G.  The organism can interfere with the delivery or supply of water for agricultural uses.

– Low (1) causes 0 or 1 of these impacts.
– Medium (2) causes 2 of these impacts.
– High (3) causes 3 or more of these impacts.

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

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

A.  The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.
B.  The pest could directly affect threatened or endangered species.
C.  The pest could impact threatened or endangered species by disrupting critical habitats.
D.  The pest could trigger additional official or private treatment programs.
E.  The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.

Score the pest for Environmental Impact. Score:

– Low (1) causes none of the above to occur.
– Medium (2) causes one of the above to occur.
– High (3) causes two or more of the above to occur.

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

Consequences of Introduction to California for Colletotrichum siamense:

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

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

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

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

–Not established (0) Pest never detected in California, or known only from incursions.
-Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).
-Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.
-High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

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

Final Score:

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

Final Score:  Score of Consequences of Introduction – Score of Post Entry Distribution and Survey Information = 12.

Uncertainty:

None.

Conclusion and Rating Justification:

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

References:

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

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

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

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

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

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

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

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

Responsible Party:

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

Comment Format:

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

Example Comment: 

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

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

♦  Comments may not be posted if they:

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

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

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

Violates agency regulations prohibiting workplace violence, including threats.

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

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

Pest Rating: B

Posted by ls

Plant Pathogens, Viruses and viroids

Hibiscus Latent Fort Pierce Virus (HLFPV)

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

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

History & Status:

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

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

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

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

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

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

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

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

California Distribution: Solano County (nursery).

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

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

Consequences of Introduction: 

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

– Low (1) Not likely to establish in California; or likely to establish in very limited areas.
– Medium (2) may be able to establish in a larger but limited part of California.
– High (3) likely to establish a widespread distribution in California.

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

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

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

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

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

– Low (1) does not have high reproductive or dispersal potential.
– Medium (2) has either high reproductive or dispersal potential.
– High (3) has both high reproduction and dispersal potential.

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

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

A.  The pest could lower crop yield.
B.  The pest could lower crop value (includes increasing crop production costs).
C.  The pest could trigger the loss of markets (includes quarantines).
D.  The pest could negatively change normal cultural practices.
E.  The pest can vector, or is vectored, by another pestiferous organism.
F.  The organism is injurious or poisonous to agriculturally important animals.
G.  The organism can interfere with the delivery or supply of water for agricultural uses.

– Low (1) causes 0 or 1 of these impacts.
– Medium (2) causes 2 of these impacts.
– High (3) causes 3 or more of these impacts.

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

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

A.  The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.
B.  The pest could directly affect threatened or endangered species.
C.  The pest could impact threatened or endangered species by disrupting critical habitats.
D.  The pest could trigger additional official or private treatment programs.
E.  The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.

Score the pest for Environmental Impact. Score:

– Low (1) causes none of the above to occur.
– Medium (2) causes one of the above to occur.
– High (3) causes two or more of the above to occur.

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

Consequences of Introduction to California for Hibiscus latent Fort Pierce virus

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

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

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

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

-Not established (0) Pest never detected in California, or known only from incursions.
–Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).
-Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.
-High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

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

Final Score:

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

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

Uncertainty:

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

Conclusion and Rating Justification:

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

References:

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

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

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

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

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

Responsible Party:

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

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Pest Rating: B

Posted by ls

Fungi, Plant Pathogens

Erysiphe aquilegiae DC. 1815

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

None.

History & Status:

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

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

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

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

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

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

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

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

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

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

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

California Interceptions: None reported.

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

Consequences of Introduction: 

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

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

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

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

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

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

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

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

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

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

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

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

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

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

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

A.  The pest could lower crop yield.

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

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

D.  The pest could negatively change normal cultural practices.

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

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

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

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

– Medium (2) causes 2 of these impacts.

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

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

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

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

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

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

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

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

Score the pest for Environmental Impact. Score:

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

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

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

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

Consequences of Introduction to California for Erysiphe aquilegiae:

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

-Low = 5-8 points

-Medium = 9-12 points

-High = 13-15 points

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

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

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

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

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

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

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

Final Score:

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

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

Uncertainty:

None.

Conclusion and Rating Justification:

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

References:

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

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

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

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

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

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

Responsible Party:

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

Pest Rating:  C

Posted by ls