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Plant Pathogens, Viruses and viroids

Cucumber Green Mottle Mosaic Virus

 California Pest Rating for
Cucumber Green Mottle Mosaic Virus
Pest Rating: A
PEST RATING PROFILE
Initiating Event:  

On December 15, 2017, Cucumber green mottle mosaic virus (CGMMV) was detected in a watermelon seed sample submitted by the USDA to the CDFA Plant Pathology Lab, and collected from a seed company’s storage facility outside of California. The seed crop was produced in California.  The seed company had originally identified the pathogen and reported its findings to the USDA.  An official identification of CGMMV was made by Tongyan Tian, CDFA plant pathologist.  Subsequent investigations are currently underway.  CGMMV is a Federal Actionable Pathogen regulated by USDA.  Currently, both agencies consider CGMMV a quarantine pathogen that is temporary, transitional and under eradication, and therefore, not established within California or anywhere else in the United States.  The current status and rating for the pathogen is reassessed here.

History & Status:

Background:  Cucumber green mottle mosaic virus is an economically important, seed transmitted pathogen known to cause significant losses in cucurbitaceous crop production in many cucurbit growing regions globally. All cucurbits are susceptible to the virus, although some are more tolerant than others (Falk et al., 2017).

Cucumber green mottle mosaic virus was originally described from the United Kingdom in 1935.  Since then, it has spread to several other regions mostly within Europe, Asia and the Middle East, most likely due to its seed-borne nature and trade of cucurbit seed from CGMMV-infected regions to non-infected regions globally.  CGMMV has also been recorded in Nigeria, Africa (Falk et al., 2017) and a possible detection of CGMMV in melon was reported from Brazil, South America, however, this record has not been confirmed (Choudhury & Lin, 1982).

The pathogen was first reported from North America in 2013, from California, USA and from Alberta, Canada.  A detailed account of its first and subsequent detections in California is given below (see ‘Detections in California’).  The first report of CGMMV in Alberta, Canada, was of infected mini-cucumber crops grown in greenhouse. The disease had been previously found in greenhouses in Ontario, British Columbia (Ling et al., 2014; Zhang et al., 2014).  In 2014, CGMMV was reported for the first time from Australia on detection of the pathogen in commercial farm-grown watermelon plants in the Northern Territory, and in 2015 and 2016 was subsequently confirmed in Queensland and Western Australia respectively (QDAF, 2017).

Biology: The virus is a species in the genus Tobamovirus (to which also belongs the well-known Tobacco mosaic virus).  The species has a positive single-stranded RNA genome and coat protein, comprised in rod-shaped particles (virions).  Several strains or isolates of CGMMV have been reported from different countries.  All strains of the virus are extremely stable in plant sap.  Infectivity is lost at 86-100 C (Type strain at 90 C) depending on viral strain. In California, although the precise source or origin of CGMMV has not been determined, research showed that the 2013 detection in Yolo County and the 2014 detections in commercial seedless watermelon production fields represented two separate introductions, as genetic analysis of those two isolates were distinct from each other (Falk et al., 2017).  The California 2013 CGMMV isolate showed 95% DNA sequence identity to those isolates reported from Russia, Spain, and Israel (Tian et al., 2014), whereas, the California 2014 CGMMV isolates and the Canada CGMMV isolates showed very similar DNA sequence identity, thereby, suggesting that they may have originated from the same source (Falk et al., 2017). The Canada CGMMV isolate showed strong sequence identity to the CGMMV Asian isolates thereby, suggesting their likely Asian origin (Zhang et al., 2014; Ling et al., 2015).

Detections in California:  In the USA, cucumber green mottle mosaic virus has only been detected in California, from 2013 to 2017.  An up-to-date account is given of those detections and subsequent regulatory actions.

 In 2013, the Cucumber green mottle mosaic virus (CGMMV) was detected in a melon field (Cucumis melo var. Saski) in Yolo County during a phytosanitary inspection for seed production.  The pathogen was identified by Tongyan Tian, CDFA Plant Pathologist, and confirmed by the USDA APHIS.  This detection marked the first record of the pathogen in California and in the United States (Tian et al., 2014; USDA APHIS, 2013; CDFA-PEA, 2013).   Three contiguous fields planted to cucumber (2 fields) and watermelon (1 field), were also determined as positive for CGMMV.  Subsequent trace back investigations revealed that the source seed for the Yolo County melon site was grown in a seed lot in Sutter County in 2012 and later, was found positive for CGMMV. The 2013 trace back also revealed that in 2012, two sites in Sutter County produced a total of 6 melon, watermelon and cucumber seed lots, of which site 1 was positive for CGMMV in all three cucurbit hosts while site 2 was negative.  Those two sites are currently planted to non-hosts of CGMMV, and in 2013, volunteer cucumber plants in site 1 tested negative for CGMMV.   Two foreign sources of melon and cucumber seed lots planted in the two Sutter County sites were identified as Chile and Romania: no (melon) seed remained for testing from the Chilean source and the Romanian cucumber seed tested positive for CGMMV.     As for the 2013 Yolo County CGMMV positive site, County and State approved abatement measures were implemented.   Eventually, wheat, a non-host, was grown at the site and in 2014, volunteer melon plants tested positive, while volunteer watermelon plants were negative.  Monitoring of volunteer plants was implemented and those in the field are treated with herbicide and biodegraded.  Furthermore, in 2013, approximately 120 trace forward seed lots were evaluated for risk of potential infection with CGMMV.  Pathways identified as possible risk links for potential CGMMV infection were source seed, shared irrigation, proximity to a positive detection, mechanical transmission (equipment and workers), and seed processing operational steps.  Trace-forward investigations revealed that 2012 Sutter County melon seeds infested with CGMMV had been shipped to Romania and Africa.  Thirty-four trace forward and trace back seed lots were sampled and tested for CGMMV of which 3 were positive for the pathogen.  In 2014, additional cucumber seed lots belonging to the 2013 trace forward lots in Sutter County tested negative for CGMMV.

In 2014, during August and September, CGMMV was detected in watermelon plant samples collected from seven watermelon production fields in Fresno, Kern, and San Joaquin Counties.  The CDFA did a trace-back to the seed lots that were linked to the CGMMV-positive fields, but found those seed lots to be negative for the pathogen.  Subsequently, the seeds were traced back to the transplant nursery and CDFA theorized that the seed lots were cross contaminated at the transplant nursery. The CGMMV-positive watermelon fields were placed on a regulatory hold (quarantine) and an abatement order was issued to growers requiring; non-host planting, equipment sanitation, other bio-security measures, and monitoring for the virus for a period of two years (Schnabel, 2017).

In 2016, during February, a seed company reported its detection of CGMMV in imported melon seed.  Consequently, the seed company voluntarily destroyed the seed lots by deep burial at a local landfill.  Later, in June 2016, a seed company reported its detection of CGMMV in seed produced in Sutter County The field had already been disked and planted with rice at the time of the report.  Nevertheless, cucurbit volunteers from the field and adjacent fields were sampled by the County and tested negative for the virus by CDFA.  The field continues to be monitored and planted to a non-host crop.  The CGMMV-positive seeds which were stored at a facility outside of California, were seized by the USDA and destroyed by incineration.  Then, in October 2016, a seed company reported its detection of CGMMV in watermelon seed produced in Yolo County. At the time of testing and reporting, the section of the field that produced the positive detection, was already fallow.  The seed company has maintained the field as fallow and will continue to notify CDFA of any volunteers, which if present, will be sampled in spring of 2018 by CDFA.  Also, the seed was voluntarily destroyed and appropriate sanitation and biosecurity measures have been implemented by the seed company (Schnabel, 2017).

In 2017, during March, a seed company reported its detection of CGMMV in watermelon seeds produced in Colusa County.  The field had already been disked and was fallow at the time of the report.  However, cucurbit volunteers and broadleaf weeds, present at the field site, were sampled and tested negative for the pathogen.  The grower continues to use appropriate best management practices including, sanitation and biosecurity measures.  The CGMMV-positive seeds which were stored outside of California, were seized by the USDA and destroyed by incineration.  In October, a seed company reported its detection of CGMMV in a watermelon seed lot produced in Sutter County.  The production field was fallow at the time of the report and any plant material recovered from the field tested negative for CGMMV.  The field will be monitored next season and the grower will be implementing sanitary and biosecurity measures.  The seed lot was seized and destroyed.  Also, at that time, CGMMV was detected in Opo squash (Lagenaria siceraria) plants grown in a small farm in Fresno County.  Fresno County issued a regulatory hold on the field as well as an abatement notice. No host crops will be grown at the site for the next two years.  The associated seeds were collected for destruction by the County.  In November, two different seed companies provided a total of four separate reports of the detection of CGMMV in watermelon seeds.  The positive seed lots were produced in Sutter, Colusa, and Glenn Counties. Trace-investigations are currently underway for each detection.  The fields were sampled and have tested negative for CGMMV. The fields will be monitored and sanitation and biosecurity measures will be implemented.  Currently, the seed lots are on hold pending voluntary destruction (Schnabel, 2017).

Plant infection:  CGMMV gains entrance into a plant through wounds, infects a few cells, moves from cell to cell (through plasmodesmata) colonizing the plant tissues and reaches the phloem where it travels systemically and infects the entire plant.

Hosts:  All cucurbit species are susceptible to CGMMV.  Main hosts include, Citrullus lanatus (watermelon), Cucumis melo (melon), C. sativus (cucumber), C. anguria (burr gherkin), Gladiolus hybrids (sword lily), Lagenaria siceraria (bottle gourd), Momordica charantia (bitter gourd), Cucurbita moschata (butternut squash), C. pepo (zucchini and button squash), C. maxima (squash), Luffa acutangula (angled luffa), L. cylindrical (smooth luffa), Benincasa hispida (winter melon), Cucumis metuliferus (horned melon), C. myriocarpus (prickly paddy melon), Citrullus colocynthis (bitter paddy melon), Trichosanthes cucumerina (snake gourd) (CABI, 2017; Falk et al., 2017). [Cech (1980) reported that the CGMMV caused apricot bare twig and unfruitfulness disease syndrome in Prunus armeniaca (apricot) only when co-infected with strawberry latent ringspot virus.]

Several experimental hosts have been tested and susceptible hosts are in three families namely, Chenopodiaceae, Cucurbitaceae and Solanaceae.  CGMMV-indicator plant species include Chenopodium album ssp. amaranticolor, Datura stramonium, and Nicotiana benthamiana.  Weeds species may be potential alternate hosts, however, currently, the role of alternate host plants in CGMMV epidemiology is not known (Falk, 2017).  Potential CGMMV weed hosts include: Amaranthus retroflexus (red root or American pigweed), Chenopodium album (lambsquarter), Heliotropium europium (Helitrope), Portulaca oleracea (pigweed), Solanum nigrum (nightshade) and Cucumis myriocarpus (paddy melon) (Falk et al., 2017).

Symptoms: Plant symptoms may vary mainly depending on virus strain, host plant species/cultivar, plant part, time of plant growth, and environmental conditions.  In general, plant symptoms may include leaf mosaic, mottling, distortion, vein clearing, and stunted growth; infected fruit can be mottled, discolored, distorted, internally discolored and deteriorated.  Root systems may be reduced.

Some Asian cultivars of cucumber only show yield losses without showing leaf symptoms.  In cucumber, the type strain causes leaf mottling, blistering and distortion, and stunted growth.  Symptoms appear 7-14 days after infection.  Usually no symptoms are produced on fruit, however, certain strains cause fruit mottling and distortion.  On the other hand, the watermelon strain can cause slight leaf mottling and dwarfing in watermelons and necrotic lesions develop on the peduncle.  Virus infection at fruit set or soon after can result in serious internal discoloration and decomposition in the fruit.

No symptoms are produced in CGMMV infected squirting cucumber (Ecballium elaterium) (CABI, 2017) – a plant native to Europe, North Africa and parts of Asia, grown sometimes for its ornamental and medicinal value. Not present in California (acc. to USDA Natural Resources Conservation Services). It is thought that infected weed species may be asymptomatic – however, this has yet to be proven.

Seed set or appearance is not affected by CGMMV and therefore, infected seed are indistinguishable from non-infected ones (Reingold et al., 2015, 2016).

Plant symptoms due to CGMMV are similar to those of other viruses in cucurbitaceous species.  Therefore, it is difficult to definitively identify the virus solely by the symptoms its causes in host plants.  For a definitive identification, serological, molecular and/or electron microscopy tests are needed.

Damage Potential: In commercial field or greenhouse environments, losses up to 100% can occur, although 40-80% losses are common (Falk et al., 2017).  Yield losses of approximately 15% in Cucurbitaceous vegetable crops are reported (Shang et al., 2011).  In Japan, considerable economic losses in watermelon have occurred.  Severe symptoms in fruit including, fruit pulp deterioration, low sugar accumulation and flavor, and distortion make fruit unmarketable and non-consumable (CABI, 2017).    In India 75%, 80% and 100% losses are reported in watermelon, muskmelon, and bottle gourd respectively. 5-16 % losses occur in cucumber yields and fruit quality.  Increased costs in production of clean planting sites and stock can be expected.  Furthermore, since the pathogen is seedborne in cucurbits, it could negatively impact export of cucurbit seeds.

Transmission: CGMMV is contagious and is transmitted by mechanical contact with contaminated sources.  It can spread through foliage contact, when plants are handled during cultivation or through grafting, when infected rootstocks are used in watermelon or cucumber cultivation.  It can survive on plant pruning equipment, clothing, hands, and machinery and be spread by agricultural practices and mechanical means (Reingold et al., 2016; USDA, 2017).  It can be transmitted from infected plant debris in soil to uninfected plants via roots.  The virus is very stable in the sap of infected plants and therefore, is able to remain active in plant debris in soil long after the death of host plant cells.  Also, it is spread through untreated irrigation water and in recirculated greenhouse water. All of these can serve as sources of inoculum.  The virus is also transmitted by pollen and seed of CGMMV-infected cucurbit plants (Liu et al., 2014) both on and within the seed coat (Hollings, et al., 1975). However, research has shown that the rate of CGMMV infection of seedlings developing from cucurbit seeds containing the pathogen, is typically 1-5% or less, under greenhouse conditions, thereby, indicating that cucurbit seeds may contain infectious CGMMV, but the virus is not always transmitted to developing seedlings (Falk, 2017).  On the other hand, high seed-transmission rates of 76% from CGMMV-infected cucumber plants, have been reported (Liu et al., 2014).

Movement of infected seed appears to be the primary means for long-distance spread, whereas, the virus is spread locally through contact, infested crop residues, and irrigation water.

CGMMV is not spread from plant to plant by specific insect or nematode vectors.   Experimentally, the cucumber leaf beetle Raphidopalpa fevicollis was shown to be a probable vector of CGMMV to test plants, whereas, the green peach aphid (Myzus persicae), the cotton aphid (Aphis gossypii) or cucumber leaf beetles (Aulacophora femoralis) did not transmit the virus (Rao & Varma, 1984).

Experimentally, CGMMV has been transmitted by dodder species (Hollings et al., 1975).

CGMMV was detected in cow dung manure and studies have demonstrated the ability of the virus to pass through the alimentary system of rodents without losing biological activity.

Worldwide Distribution: Asia: China, India, Iran, Israel, Japan, Republic of Korea, Lebanon, Myanmar, Pakistan, Saudi Arabia, Sri Lanka, Syria, Taiwan, Thailand, Turkey;

Africa: Nigeria; North America: Canada, USA (California: temporary, transitional, and under eradication); Europe: Austria, Bulgaria, Czechoslovakia (former), Denmark, Finland, Germany, Greece, Hungary, Latvia, Lithuania, Moldova, Netherlands, Norway, Romania, Russian Federation, Spain, Sweden, Ukraine, United Kingdom and Yugoslavia (former); Oceania: Australia (CABI, 2017; Ling & Li, 2013; Tesoriero et al., 2016).

An unconfirmed record of CGMMV is from Brazil, South America (CABI, 2017)

Official Control: Currently, the following countries include CGMMV on their ‘Harmful Organism’ lists: Chiles, China, Colombia, Ecuador, Georgia, Guatemala, Honduras, Indonesia, Japan, New Zealand, Nicaragua, Panama, Paraguay, Peru, Syrian Arab Republic, Thailand, and Timor-Leste (USDA PCIT, 2017).

In the USA, CGMMV is a Federal Actionable Pathogen of quarantine concern and is considered temporary, transitional and under eradication.  Currently, CGMMV is an A-rated, quarantine actionable pathogen in California.

California Distribution:  CGMMV is not established in California.

California Interceptions: There are no state reports of CGMMV detections in plant materials intercepted within or at points of entry in California.

The risk Cucumber green mottle mosaic virus would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: Since its first detection in 2013, there have been repeated incidences of field detections that directly indicate that CGMMV is likely to establish a widespread distribution in all cucurbit-growing regions within California.

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

Score: 3

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

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

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

2) Known Pest Host Range: CGMMV has a moderate range of cucurbitaceous host plants which are commonly grown mostly in the warmest areas of California, such as the San Joaquin Valley, the Sacramento, Valley and the low desert valleys.

Evaluate the host range of the pest.

Score: 2

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

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

3) Pest Dispersal Potential: CGMMV is capable of high reproduction and widespread dispersal mainly as it is highly contagious and is easily transmitted through mechanical, plant and human contact, irrigation water and water in contact with infected crop debris.  It can be widely dispersed over long distance through infected seed, and is highly stable and remains active in infected plant debris in soil.

Evaluate the natural and artificial dispersal potential of the pest.

Score: 3

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

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

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

4) Economic Impact: CGMMV is capable of significantly lowering crop yield and value thereby, increasing crop production costs.  It can result in the loss of markets through the imposition of quarantines by domestic and international trade partners, change in cultural practices, including adoption of a non-host crop period in infested and treated fields for 3-5 or more years, and alteration of delivery and distribution of irrigation water to and from infested fields.  Furthermore, significant losses in seed and transplant production can result due to a CGMMV infestation.

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

Economic Impact: A, B, C, G

A. The pest could lower crop yield.

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

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

D. The pest could negatively change normal cultural practices.

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

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

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

Economic Impact Score: 3

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

– Medium (2) causes 2 of these impacts.

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

5) Environmental Impact: Detection and establishment of CGMMV would significantly impact existing cultural practices, as well as those followed for home/urban gardening and ornamental production.  Subsequently, it could result in the implementation of additional and costly official and home/urban treatment programs.

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

Environmental Impact: D, E

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

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

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

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

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

Environmental Impact. Score: 3

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

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

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

Consequences of Introduction to California for Cucumber green mottle mosaic 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 to California = 14 (High)

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

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

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

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

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

Evaluation is ‘Not Established (0)’:  Similar and subsequent to its original detection in 2013, all incidences of Cucumber green mottle mosaic virus detections (detailed above in ‘Detections in California’) have resulted in eradicative actions.  The viral pathogen is, therefore, not considered as established in California and continues to be ‘transient, temporary and under eradication’.

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 = 14.

Uncertainty:

Currently, the precise origin or source of CGMMV introduction into the USA is not known for certain.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Cucumber green mottle mosaic virus continues as A.

References:

Abatement Notice.  2013.  (  ) Seed Company, Cucumber green mottle mosaic virus (CGMMV) Acidovorax avenae subsp. citrulli (BFB) abatement notice.  County of Yolo, John Young Agricultural Commissioner.

CABI   2017.  Cucumber green mottle mosaic virus (white break mosaic) datasheet.  Crop Protection Compendium.  http://www.cabi.org/cpc/datasheet/16951

Cech M., M. Filigarova, J. Pozdena, and H. Branisova.  1980. Strawberry latent ringspot and cucumber green mottle mosaic viruses in apricots with the bare twig and unfruitfulness disease syndrome. Acta Phytopathologica Academiae Scientiarum Hungaricp, 15:391-396

CDFA-PEA.  2013.  Cucumber green mottle mosaic virus and Bacterial fruit blotch detection in California.  Pest Exclusion Advisory no. 29-2013.  California Department of Food and Agriculture, November 27, 2013.

Choudhury, M. M., and M. T. Lin.  1982.  ‘Ocorrência de viroses em plantas de melão e abobrinha na região do sub-médio São Francisco’, EMBRAPA Pesquisa am Andamento, vol. 14, no. 4, pp. 1–2.

Falk, B. W., T. L. Pitman, B. Aegerter, and K-S. Ling.  2017. Recovery Plan for Cucumber green mottle mosaic virus.  Plant Diseases That Threaten U. S. Agriculture Identified and Prepared for Under the National Plant Disease Recovery System.  USDA ARS. https://www.ars.usda.gov/office-of-pest-management-policy/npdrs/ Last modified 3/7/2017.

Hollings M, Y. Komuro, and H. Tochihara.  1975.  Descriptions of Plant Viruses No. 154. Wellesbourne, UK: AAB, 4 pp.

Ling, K. S., and R. Li.  2014.  First report of cucumber green mottle mosaic virus infecting greenhouse cucumber in Canada.  Plant Disease 98 (5): 701.

Liu, H. W., L. X. Luo, J. Q. Li, P. F. Liu, X. Y. Chen,  and J. J. Hao.  2014.  Pollen and seed transmission on Cucumber green mottle mosaic virus in cucumber.  (Published online 17 April 2013.)  Plant Pathology (2014) 63, 62-77.

Lovig, E.  2014.  Email communication from E. Lovig, CDFA, to A. Morris and J. Chitambar, CDFA.  Subject: Cucumber green mottle mosaic virus (CGMMV) and Bacterial fruit blotch (BFB) detections in California.  Dated April 29, 2014.

NPAG.  2013.  Cucumber green mottle mosaic virus (CGMMV).    New Pest Advisory Group, Plant Epidemiology and risk Analysis Laboratory, Center for Plant Health Science & Technology, USDA-APHIS.  NPAG Report 20130819.docx, August 19, 2013: 1-9.

QDAF.  2017.  Cucumber green mottle mosaic virus. The State of Queensland Department of Agriculture and Fisheries, Queensland Government. https://www.daf.qld.gov.au/plants/health-pests-diseases/a-z-significant/cucumber-green-mottle-mosaic-virus# Last updated 01 March, 2017.

Rao A. L. N, and A. Varma. 1984. Transmission studies with cucumber green mottle mosaic virus. Phytopathologische Zeitschrift, 109(4):325-331.

Shang, J., Y. Xie, X. Zhou, Y. Qian, and J. Wu.  2011.  Monoclonal antibody-based serological methods for detection of Cucumber green mottle mosaic virus.  Virology Journal 8:228.

Schnabel, D.  2017.  Email from D. Schnabel, CDFA, to S. Brown and J. Chitambar, CDFA.  Subject: CGMMV. Dated December 11, 2017, 7:16 am.

Reingold V., E. Lachman, A. Koren, and A. Dombrovsky.  2015.  Seed disinfection treatments do not sufficiently eliminate the infectivity of Cucumber green mottle mosaic virus (CGMMV) on cucurbit seeds.  Plant Pathology 64: 245-255.

Reingold V., E. Lachman, O. Beelausov, A. Koren, N. Mor, and A. Dombrovsky.  2016. Epidemiological study of Cucumber green mottle mosaic virus in greenhouses enables reduction of disease damage in cucurbit production. Annals of Applied Biology 168:29-40.

Technical Working Group Responses: Cucumber green mottle mosaic virus.  October 28, 2013.  United States Department of Agriculture, Animal and Plant Health Inspection Service, Plant Protection and Quarantine.

Tesoriero, L. A., G. Chambers, M. Srivastava, S. Smith, B. Conde, and L. T. T. Tran-Nguyen.  2016.  First report of cucumber green mottle mosaic virus in Australia. Australasian Plant Disease Notes, 11:1. http://link.springer.com/article/10.1007/s13314-015-0186-x

Tian, T., K. Posis, C. J. Maroon-Lango, V. Mavrodieva, S. Haymes, T. L. Pitman, and B. W. Falk.  2014.  First report of Cucumber green mottle mosaic virus in melon in the United States.  Plant Disease 98:1163.

USDA APHIS.  July 25, 2013.  Email communication from K. J. Handy, CAPS Database Manager, USDA APHIS PPQ, PDEP to R. A. Bailey (and other APHIS members)  Director, PHPPS, CDFA. Subject: FW: confirmed id: Cucumber green mottle mosaic virus (CGMMV) detection in melon in CA – new US record.

USDA PCIT.  2017.  USDA Phytosanitary Certificate Issuance & Tracking System. December 14, 2017, 3:49:31 pm CDT. https://pcit.aphis.usda.gov/PExD/faces/ReportHarmOrgs.jsp

Zhang, J. W., K-S. Ling, and R. Cramer.  2014.  New Cucumber threat studied.  https://www.greenhousecanada.com/inputs/crop-protection/march-april-2014-4021

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: A

Posted by ls

Plant Pathogens, Viruses and viroids

Freesia Mosaic Virus

California Pest Rating for
Freesia Mosaic Virus
Pest Rating: B
PEST RATING PROFILE
Initiating Event:

On March 21, 2016, two samples of diseased Lilium sp. (lily) plants exhibiting leaf spots, were collected from a nursery in San Luis Obispo County, during a regulatory nursery inspection by San Luis Obispo County Agricultural officials, and sent to the CDFA Plant Pathology Laboratory for analysis.  Tongyan Tian, CDFA plant pathologist, identified two pathogens associated with the sample, namely, Freesia mosaic virus (FreMV) and Freesia sneak virus (FreSV). Freesia mosaic virus was assigned a temporary Q rating by the CDFA, whereas FreSV already has a permanent B rating.  Subsequently, all infected propagative plant material was destroyed.  The risk of infestation of FreMV in California is evaluated and a permanent rating is proposed here.

 History & Status:

Background:  Freesia mosaic virus is a plant virus belonging to the genus Potyvirus in the family Potyviridae, and is vectored by the potato aphid, Macrosiphum euphoribae and green peach aphid, Myzus persicae.   Freesia mosaic virus (FreMV) was originally reported from Freesia refracta, in Lisse, the Netherlands, by Van Koot et al. in 1954 (Brunt, et al., 1996 onwards; Van Koot et al., 1954).  This pathogen, along with few other plant virus pathogens, has been reported to naturally infect freesia plants (Van Koot et al., 1954; Bouwen, 1994).  In the Netherlands, Freesia mosaic virus was frequently found in field samples of freesia plants with and without symptoms of freesia leaf necrosis disease and, more or less frequently in double infections with Freesia sneak virus in the same plants (Vaira et al., 2006; Meekes & Verbeek, 2011).  Freesia leaf necrosis disease has been reported in Europe since the 1970s and double infections of FreMv and FreSV in freesia plants were first described as “severe leaf necrosis” or “complex disease” which is progressive and may cause death of plants before flowering (Van Dorst, 1973; Meekes & Verbeek, 2011).  The natural occurrence of FreMV has also been found in Peruvian lily in Italy, and besides its spread in Europe, the pathogen has been reported from Freesia spp. in India, Australia, Korea, and New Zealand (Bellardi, 1992; Brunt et al., 1996 onwards; Kumar, et al., 2008; Jeong et al., 2014).

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

Hosts: Freesia spp. F. refracta, (common freesia; Iradaceae) and Alstroemeria sp. (Peruvian lily; Alstroemeriaceae).  Freesia and Peruvian lily are monocots and although presently naturalized in several countries including the USA, both plant species are native to South Africa and South America respectively (Bellardi, 1992; Brunt et al., 1996 onwards). Freesia mosaic virus was also detected in Lily (Lilium sp.) by the CDFA (see ‘Initiating Event’) and is included as an associated host.

Symptoms:  Symptoms of Freesia mosaic virus-infected freesia plants include mild chlorosis. The pathogen may also be present in symptomless plants (Brunt et al., 1996 onwards).  Experimentally, Alstroemeria sp. plants that were mechanical inoculated FMV infested plant sap, failed to show symptoms three months after inoculation, although the virus was detected serologically (Bellardi, 1992).

Complex infections of Freesia mosaic virus and Freesia sneak virus may result in severe leaf necrosis showing symptoms of chlorotic spots and stripes that appear on the first leaf of freesia plants grown from corms, and later turn grey-brown and necrotic as the disease progresses rapidly often resulting in rot of corms, and death of plants before flower formation (Van Dorst, 1973).

Damage Potential: In California, nursery and private productions of freesia and lily plants may be impacted if infected with FreMV.

Transmission: In nature, Freesia mosaic virus is transmitted by the potato aphid, Macrosiphum euphorbiae and green peach aphid, Myzus persicae.  It is also transmitted by mechanical inoculation and spread via infected nursery plants and propagative parts.   The virus pathogen is not transmitted by seed, pollen or contact between plants (Brunt et al., 1996 onwards).

Worldwide Distribution:  Asia: India, Korea; Europe: United Kingdom, Ireland, Italy, the Netherlands; North America: USA (Virginia); Australia; New Zealand (found, but with no evidence of spread) (Bellardi, 1992; Brunt, et al., 1996 onwards; Kumar et al., 2008; Jeong et al., 2014; Vaira et al., 2009).

Official Control: Freesia mosaic virus is on the ‘Harmful Organism List’ for Colombia, Georgia, Israel, Japan, Peru, and Taiwan (USDA-PCIT, 2016).  Currently, FreMV has a temporary Q-rating in California.

California Distribution: San Luis Obispo (nursery).

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

The risk Freesia mosaic 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 mosaic virus is likely to establish wherever freesia and Peruvian lily and lily plants are grown in limited areas of California. These host plant species have limited production in state, mostly in the north coast and mountain regions, and few southern coast regions, as well as cultivated in nursery and private production sites – including home gardens.       

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 mosaic virus is limited to Freesia spp. (Iradaceae), Alstroemeria sp. (Alstroemeriaceae), and Lilum spp. (Liliaceae).

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 mosaic virus has high reproductive potential.  In nature, its spread to non-infected plants is through aphid vectors, Macrosiphum euphorbiae and Myzus persicae.  It is also transmitted by mechanical inoculation and spread via infected nursery plants and propagative parts.   The virus pathogen is not transmitted by seed, pollen or contact between plants.

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

A. The pest could lower crop yield.

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

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

D. The pest could negatively change normal cultural practices.

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

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

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

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

– Medium (2) causes 2 of these impacts.

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

Risk is High (3) – Incidents of Freesia mosaic virus infections could lower plant value resulting in loss in market sales of nursery-grown freesia and lily plants.  The pathogen is vectored by the potato aphid and green peach aphid, Macrosiphum euphorbiae and Myzus persicae respectively.

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) – Plant infections caused by Freesia mosaic virus are likely to have a minimal impact on the overall environment but may significantly impact home gardening and ornamental plantings. The pathogen may impact California State and federal endangered western lily (Lilium occidentale) and Pitkin Marsh lily (L. pardalinum ssp. pitkinense (ref: State and Federally listed endangered, threatened, and rare plants of California, July, 2015, California Department of Fish and Wildlife, Biogeographic Data Branch, California Natural Diversity Database).

Consequences of Introduction to California for Freesia mosaic 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 mosaic virus to California = 10.

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

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

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

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

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

Evaluation is not established.  Freesia mosaic 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 = 10.

Uncertainty:

Currently, the possible distribution of Freesia mosaic virus in California is not known.  Future confirmed detection of its in-state presence and distribution may affect its overall score and alter its current proposed rating.

Conclusion and Rating Justification:

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

References:

Bellardi, M. G.  1992.  Natural occurrence of Freesia mosaic virus in Alstroemeria sp.  Plant Disease 76:643. DOI: 10.1094/PD-76-0643B.

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

Brunt, A.A., K. Crabtree, M. J. Dallwitz, A. J. Gibbs, L. Watson, and  E. J. Zurcher. (eds.) (1996 onwards). `Plant Viruses Online: Descriptions and Lists from the VIDE Database. Version: 16th January 1997.’ URL http://biology.anu.edu.au/Groups/MES/vide/

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.

Kumar, Y., V. Hallan, and A. A. Zaidi.  2008.  First finding of Freesia mosaic virus infecting freesia in India.  New Disease Reports 18:3. http://www.ndrs.org.uk/article.php?id=018003.

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.

USDA- PCIT.  2016.  USDA Phytosanitary Certificate Issuance & Tracking System. June 6, 2016.  https://pcit.aphis.usda.gov/PExD/faces/ReportHarmOrgs.jsp .

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.

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

Van Koot, Y., D. H. M. van Slogteren, M. C. Cremer, and J. Camfferman.  1954.  Virusverschijnselen in freesia’s.  Tijdschrlfot over Planienziekten 60:157-192

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

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

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

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:

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

Plant Pathogens, Viruses and viroids

Bamboo Mosaic Virus (BaMV)

California Pest Rating for 
Bamboo Mosaic Virus (BaMV)
Pest Rating:  B
PEST RATING PROFILE
Initiating Event: 

None.

History & Status:

Background:  Bamboo mosaic virus was originally isolated from two species of bamboo, Bambusa multiplex and B. vulgaris, in Brasilia, Brazil and reported as a new virus as well as the first virus identified infecting bamboo plants.  No evidence of spread in Brazil was observed outside the original site. (Lin et al., 1977).  Since then, the virus pathogen has also been reported from the Pacific islands, Taiwan, Australia, the Philippines, and the USA.  In the USA, Bamboo mosaic virus was first reported from San Diego, California, in Beechey bamboo plants growing in the San Diego Zoo (Lin et al., 1995).  During April 2014, BaMV was detected in bamboo growing in San Diego Botanic Garden.  This detection was made by the CDFA Plant Pathology Laboratory.   The pathogen is reported to have been tentatively diagnosed in a Bambusa sp. sample in Florida during the 1980s, although bamboo enthusiasts in Florida claim to have observed virus-like symptoms in the collections prior to the 1980s (Elliott & Zettler, 1996). The pathogen has also been reported from Hawaii in B. vulgaris (Nelson & Borth, 2011).

Bamboo mosaic virus is a plant pathogenic virus in the genus Potexvirus within the family Potexvirus.

Hosts: Bamboo is the natural host.  Ten species of bamboo are included namely, Bambusa beecheyana, B. beecheyana cv. pubescens, B. edulis, B. multiplex, B. oldhamii, B. vulgaris, B.vulgaris var. striata, Dendrocalamus latiflorus, D. latiflorus cv. ‘Mei-nung’, Phyllostachys nigra.  Experimental susceptible plants include Gomphrena globosa, Chenopodium amaranticolor, Bambusa vulgaris ‘Vittata’, and Dendrocalamus latiflorus cv. ‘Mei-nung’ (Brunt et al., 1996 onwards).

Symptoms: Bamboo mosaic virus-infected bamboo plants may exhibit chlorotic mosaic and mottling patterns running parallel to the leaf veins, necrotic streaks on shoots and culms, vascular discoloration, aborted stems and death of plants.  Symptoms may be mild or subtle in some infected plants (Brunt et al., 1996; Nelson & Borth, 2011).

Damage Potential:  Bamboo mosaic virus can affect growth and stand of infected bamboo plants.  While quantitative crop loss values have not been reported, the pathogen has the potential to cause losses in production and is considered a threat to the bamboo industry in Taiwan (Lin et al., 1993).  In California, mainly nursery, private and commercial cultivations of bamboo in public parks, landscapes, and gardens are at risk of reductions in healthy stands if infected with BaMV.  Furthermore, once established, the disease cannot be eradicated without destroying infected plants (Nelson & Borth, 2011).

Transmission: Bamboo mosaic virus is mechanically transmitted to non-infected bamboo cultivars.  Contaminated cultivation tools and infected BaMV bamboo plants are a means for spreading the virus.  Transmission does not involve an insect vector.

Worldwide Distribution:  Asia: Philippines, Taiwan; North America: USA; South America: Brazil; Australia: Queensland, Western Australia (Brunt et al., 1996 onwards; Dodman & Thomas, 1999; Elliot & Zettler, 1996; Lin et al., 1977; Lin et al., 1993, 1995)

Official Control: Bamboo mosaic virus is on the ‘Harmful Organism List’ for Costa Rica, French Polynesia, Georgia, India, Japan, and New Zealand (PCIT, 2015).  Currently, BaMV has a temporary Q rating in California.

California Distribution: San Diego, San Diego County.

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

The risk Bamboo mosaic 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) – Bamboo mosaic virus is likely to establish within California wherever bamboo is grown in southern and northern 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) – The host range is limited to bamboo – the natural host. Ten species of bamboo are included namely, Bambusa beecheyana, B. beecheyana cv. pubescens, B. edulis, B. multiplex, B. oldhamii, B. vulgaris, B.vulgaris var. striata, Dendrocalamus latiflorus, D. latiflorus cv. ‘Mei-nung’, Phyllostachys nigra.

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) – Bamboo mosaic virus increases rapidly within infected bamboo plants and can be spread to new non-infected sites through movement of infected plants.  The virus is also mechanically transmitted through infected cultivation tools such as those used in pruning.  It is not spread by an insect or other biological vector.

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) – Infections by Bamboo mosaic virus could lower crop yield and value, increase production costs due to removal and replacement of diseased plants, and trigger loss of domestic and international markets.  In particular, nurseries could be negatively affected by losses in production and sale.

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) – In California, bamboo is mainly grown in specialty nurseries, public parks, landscapes, and garden environments.  Healthy bamboo stands in such environments could be significantly impacted if infected with Bamboo mosaic virus.

Consequences of Introduction to California for Bamboo mosaic 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 BaMV 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 Low (-1).  Presently, Bamboo mosaic virus is established in San Diego, 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 Bamboo mosaic virus is B.

References:

Brunt, A.A., K. Crabtree, M. J. Dallwitz, A. J. Gibbs, L.Watson, and E. J. Zurcher (eds.). (1996 onwards). `Plant Viruses Online: Descriptions and Lists from the VIDE Database. Version: 20th August 1996.’ URL http://biology.anu.edu.au/Groups/MES/vide/.

CABI.  2015.  Bamboo mosaic virus datasheet (basic). Crop Protection Compendium.  http://www.cabi.org/cpc/datasheet/1695.

Dodman, R.L., and J. E. Thomas. 1999. The first record of Bamboo mosaic potexvirus from Australia. Australasian Plant Pathology 28:337–337.

Elliot, M.S., and F. W. Zettler. 1996. Bamboo mosaic virus detected in ornamental bamboo species in Florida.  Proceedings of the Florida State Horticultural Society 109:24–25.

Lin, M. T., E. W. Kitajima, F. P. Cupertino, and C. L. Costa.  1977.  Partial purification and some properties of Bamboo mosaic virus.  Phytopathology 67:1439-1443.

Lin, N. -S., Y.-J. Chai, T. -Y. Chang, and Y. -H. Hsu.  1993.  Incidence of Bamboo mosaic potexvirus in Taiwan.  Plant Disease 77:448-450.

Lin, N. –S., B. –Y. Lin, T. –Y. Yeh, and Y. -H. Hsu.  1995.  First report of Bamboo mosaic virus and its associated satellite RNA on bamboo in the U. S.  Plant Disease 79 (12):1249.

Nelson, S., and W. Borth.  Bamboo Mosaic.  2011.  College of Tropical Agriculture and Human Resources University of Hawai’i at Mānoa, Plant Disease September 2011 PD-76.

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

Fazzio, D.  2015.  Bamboo.  Sonoma County Master Gardeners University of California.  http://ucanr.edu/sites/scmg/Plant_of_the_Month/Bamboo/# .

Responsible Party:

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

Pest Rating:  B

Posted by ls

Plant Pathogens, Viruses and viroids

Tomato Yellow Leaf Curl Virus (TYLCV)

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

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

History & Status:

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

California Distribution: Imperial and Riverside Counties.

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

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

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

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

Consequences of Introduction: 

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Score the pest for Environmental Impact:

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

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

Consequences of Introduction to California for Tomato yellow leaf curl virus

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

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

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

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

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

Evaluation is Low (-1). 

Final Score:

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

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

Uncertainty:

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

Conclusion and Rating Justification:

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

References:

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

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

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

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

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

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

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

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

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

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

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

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

Responsible Party:

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

PEST RATING: B

Posted by ls

Plant Pathogens, Viruses and viroids

Pea Seed-borne Mosaic Virus (PSbMV)

California Pest Rating for
Pea Seed-borne Mosaic Virus (PSbMV)
Pest Rating: B
PEST RATING PROFILE
Initiating Event: 

There is no initiating event.  The risk of infestation of Pea seed-borne mosaic virus in California is evaluated and a permanent rating is proposed.

History & Status:

Background: In 1966 a virus disease of pea was first reported in Europe.  The same virus was also described in Japan as Pea seed-borne mosaic virus. During the early 1980s the virus was also discovered in New Zealand and England and is now known to be widespread throughout the globe due to the movement of infected pea seeds through high international trade.  In California, the pathogen was first discovered in 2004 on pea cultivated in a field in Monterey County.

Pea seed-borne mosaic virus belongs to the genus Potyvirus in the family Potyviridae and RNA viruses group.  The nucleic acid consists of a positive-sense single stranded RNA.  The virus consists of several strains or pathovars that are serologically closely related.  Three strains of PSbMV (P1, P2 and P4) have been identified and the most common strains include P-1 and P-4 from pea and the L-1 from lentil. Usually, differential hosts have been used to identify specific strains (Larsen, 2001).

Hosts: The host range for PSbMV includes at least 47 plant species belonging to 12 families.  However, only three hosts are considered to be economically important, namely, Pisum sativum (pea), Lens culinaris subsp. culinaris (lentil), and Vicia faba (bean).  Chickpea is also a susceptible host however, there is no evidence that it transmitted through contaminated seed.  Other hosts include a wide range of experimental hosts.

Symptoms:  Symptoms on peas are affected by age of plant at the time of infection, temperature, virus strain or pathotype and plant genotype.  Symptoms may develop in as few as 3 days after infection.  Certain pea cultivars never express symptoms (Khetarpal & Maury, 1987). Symptoms may be more severe on plants germinating from infected seed.  Symptoms include general stunting, leaf mild chlorosis, shortening and downward rolling of leaflets, vein clearing and swelling, rosetting (due to reduction of internodal growth), mosaic, distorted flower or seed pods and failure to set pods. However, symptoms disappear soon after infection.  Seed coats of PSbMV-infected seed may become cracked, split or banded and often serve as indicators of possible PSbMV infection although these symptoms may also be caused by physiological or environmental factors.  Contrarily, healthy appearing seeds with normal seed coats may also bear the virus pathogen (CABI, 2014; Larson, 2001).

Damage Potential:  The loss of market due to infected seed is a significant factor in the estimated economic loss caused by the virus.  As much as 36% reduction in pea seed yields are estimated to be due to PSbMV infection (Khetarpal & Maury, 1987).  Seed infections greater than 30% have been reported (CABI, 2014).

Transmission:  The most common means of long-distance transmission of PSbMV is through infected seed.  The virus infects seed internally and all parts of inflorescences from infected plants contain the virus.  Infected seed is an important means of introducing the virus into new, non-infected areas.  Spread from plant to plant is brought about mainly by aphid vectors and mechanical transmission. The virus can be transmitted in a non-persistent manner by 21 aphid species.   The pea aphid (Acyrthosiphon pisum), green peach aphid (Myzus persicae), and cotton aphid (Aphis gossypii) are the most common vectors.  Natural aphid vectors are the pea aphid, cowpea aphid (Aphis craccivora), black bean aphid (Aphis fabae), Dactynotus escalanti, mint aphid (Ovatus crataegarius), and bird cherry-oat aphid (Rhopalosiphum padi). If aphid populations are high and uncontrolled during a growing season, then only a few PSbMV-infected seeds can result in spreading the disease over a large percentage of a field.  Typically, the aphid vector can acquire the virus in 5 min and transmit it after a single probe of one minute or less (Larsen, 2001).  Hampton and Mink (1975) reported that aphids acquire PSbMV and inoculate it in 10-90 sec feeding periods without requiring a latent period.  High aphid populations are favored by cool growing seasons thereby enabling effective spread of PSbMV.

Worldwide Distribution:   PSbMV is distributed worldwide largely due to the distribution of pea germplasm infected with the seed-transmitted virus (Larsen, 2001; Hampton et al., 1993).  It is distributed in Asia: India, Iran, Israel, Japan, Jordan, Lebanon, Nepal, Pakistan, Syria, Taiwan, Turkey, Yemen; Africa: Algeria, Egypt, Ethiopia, Libya, Morocco, South Africa, Sudan, Tanzania, Tunisia, Zambia, Zimbabwe; North America: Canada, USA; South America: Brazil; Europe: Belgium, Bulgaria, Czech Republic, former Czechoslovakia, Denmark, Finland, France, Germany, Netherland, Poland, Romania, Russian Federation, Serbia, Slovakia, Sweden, Switzerland, United Kingdom, Yugoslavia; Oceania: Australia, New Zealand.

In the USA is it has been found in California, Idaho, Maryland, Minnesota, New York, Oregon, Vermont, Washington, and Wisconsin (CABI, 2014; EPPO, 2014).

Official Control:  Since 1995, PSbMV has been listed by Argentina and Brazil as an A1 quarantine pathogen (EPPO, 2014).  The pathogen is on the ‘Harmful Organism List’ for nine countries: Australia, Costa Rica, Georgia, Japan, Nambia, Nauru, South Africa, Taiwan and Uruguay (PCIT, 2014).

California Distribution: Monterey County, California.

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

The risk Pea seed-borne mosaic virus would pose to California is evaluated below.

Consequences of Introduction: 

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

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

Risk is Medium (2) – The establishment of PSbMV within CA is closely related to the establishment of its major hosts and associated aphid vector. Cultivation of pea and bean plants requires cool and humid climate – such as is found mainly along the California’s coastal regions.  Already PSbMV is established in Monterey County, 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 Medium (2) – PSbMV has a moderate host range of 47 plant species belonging to 12 families.  However, the main hosts of economic importance are pea, bean and lentil.  The former two crops are in limited commercial production in California.

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

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

Risk is High (3) – The spread of PSbMV is through infected seed and several (21) Aphid species.  The combination of both agents, plus the high rate of multiplication of the virus within an infected host render the pathogen a high risk potential for spread 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) –Incidence and spread of PSbMV could adversely affect pea and bean production in California by lowering crop yield, value, increasing production costs, affecting local and international  markets, negatively change normal cultivation practices to prevent incidence of further occurrence and spread of the virus and its whitefly vector.

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

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

Score the pest for Environmental Impact. Score:

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

Risk is Medium (2) – Several weeds may be hosts of PSbMV and serve as sources of inoculum acquired by aphids against economically important hosts. However, several weed hosts may be asymptomatic and it is not known how well the whitefly vector will acquire the virus from such infected hosts that may comprise natural environments.  The effect on these hosts in nature is not known.  Nevertheless, PSbMV infections may impact home/urban gardening and cultivation of ornamentals.

Consequences of Introduction to California for Peas seed-borne mosaic 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 PSbMV 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 (-1). 

Final Score:

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

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

Uncertainty:

Current field data is always needed on the probable establishment and spread of PSbMV beyond the known infested regions of Monterey County.  Such information would be obtained through periodic surveys.  Also not known is the distribution of the virus in natural environments and the potential that infected natural hosts may play in its possible spread to legume fields.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Pea seed-borne mosaic virus is B.

References:

CABI   2014.  Pea seed-borne mosaic virus full datasheet.  Crop Protection Compendium.  http://www.cabi.org/cpc/datasheet/1695

EPPO, 2014.  Pea seed-borne mosaic virus (PSBMV0).  New PQR database.  Paris, France:  European and Mediterranean Plant Protection Organization.  http://newpqr.eppo.int

Hampton, R. O and G. I. Mink. 1975. Pea seed-borne mosaic virus. CMI/AAB Descriptions of Plant Viruses. No. 146, 4pp. Wellesbourne, UK: Association of Applied Biologists. http://www.dpvweb.net/dpv/showdpv.php?dpvno=146.

Hampton, R. O, J. M. Kraft, F. J. Muehlbauer. 1993. Minimizing the threat of seedborne pathogens in crop germ plasm: elimination of pea seedborne mosaic virus from the USDA-ARS germ plasm collection of Pisum sativum. Plant Disease, 77(3):220-224

Khetarpal R. K. and Y. Maury. 1987. Pea seed-borne mosaic virus: a review. Agronomie, 7(4):215-224

Larsen, R. C.  2001.  Pea Seedborne mosaic virus.  In: Compendium of Pea Diseases and Pests Second Edition.  St.Paul, USA: APS Press, 37-38.

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

Responsible Party:

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

Pest Rating: B

Posted by ls