Category Archives: Plant Pathogens

Plant Pathology (plant diseases)

Ilyonectria capensis L. Lombard & Crous 2013

California Pest Rating Proposal

Ilyonectria capensis L. Lombard & Crous 2013  
Current Pest Rating: Q
Proposed Pest Rating: C


Comment Period:  2/22/2019 – 4/8/2019*


Author/Responsible Party:

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


*NOTE:

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


Comment Format:

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

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


Posted comments will not be able to be viewed immediately.


Comments may not be posted if they:

  • Contain inappropriate language which is not germane to the
    pest rating proposal;
  • Contains defamatory, false, inaccurate, abusive, obscene, 
    pornographic, sexually oriented, threatening, racially offensive,
    discriminatory or illegal material;
  • 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.


Proposed Pest Rating: C


Posted by ls 

Neocercosporidium smilacis (Thüm.) U. Braun, C. Nakash., Videira & Crous 2017

California Pest Rating Proposal

Neocercosporidium smilacis (Thüm.) U. Braun, C. Nakash., Videira & Crous 2017
Current Pest Rating: Q
Proposed Pest Rating: B


Comment Period: 2/22/2019 – 4/8/2019*

Author/Responsible Party:

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


*NOTE:

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


Comment Format:

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

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


Posted comments will not be able to be viewed immediately.


Comments may not be posted if they:

  • Contain inappropriate language which is not germane to the
    pest rating proposal;
  • Contains defamatory, false, inaccurate, abusive, obscene,
    pornographic, sexually oriented, threatening, racially offensive,
    discriminatory or illegal material;
  • 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.


Proposed Pest Rating: B


Posted by ls 


Cucurbit Chlorotic Yellows Virus

California Pest Rating Proposal

Cucurbit chlorotic yellows virus
Current Pest Rating: Not Rated
Proposed Pest Rating: B


Comment Period: 2/20/2019 – 4/6/2019*


Author/Responsible Party:

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


*NOTE:

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


Comment Format:

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

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


Posted comments will not be able to be viewed immediately.


Comments may not be posted if they:

  • Contain inappropriate language which is not germane to the
    pest rating proposal;
  • Contains defamatory, false, inaccurate, abusive, obscene,
    pornographic, sexually oriented, threatening, racially offensive,
    discriminatory or illegal material;
  • 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.


Proposed Pest Rating: B


Posted by ls 

Gymnosporangium yamadae

California Pest Rating Proposal

Gymnosporangium yamadae Miyabe ex G. Yamada 1904
Current Pest Rating: Q
Proposed Pest Rating: A


Comment Period: 1/18/2019 – 3/4/2019*


Responsible Party:

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


*NOTE:

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


Comment Format:

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

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

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

♦  Comments may not be posted if they:

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

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

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.


Proposed Pest Rating: A


Posted by ls 

Tomato Brown Rugose Fruit Virus

California Pest Rating for
Tomato Brown Rugose Fruit Virus
Pest Rating:      A

PEST RATING PROFILE

Initiating Event:

On September 25, 2018, Tongyan Tian, CDFA Plant Pathologist, was notified by Kai-Shu Ling, Plant Pathologist, USDA ARS, Charleston, South Carolina, of his detection of Tomato brown rugose fruit virus (ToBRFV) in a tomato plant tissue sample sent to him by a private company in California.   The sample had been collected from tomato plants grown in the company’s greenhouse in Santa Barbara County.  On September 13, 2018, the company had also sent an unofficial symptomatic tomato leaf sample to CDFA for diagnosis of the associated pathogen. On November 2, 2018, Tongyan Tian, CDFA, identified the associated pathogen as Tomato brown rugose fruit virus. On further investigation of the situation in California, CDFA was notified by the company that all ToBRFV-infested and symptomatic plant material had been voluntarily destroyed, thereby preventing the collection of an official sample. Nevertheless, the risk associated with the possible introduction of ToBRFV and a proposed rating for this pathogen is documented here.

History & Status:

Background:  Tomato brown rugose fruit virus is a relatively new Tobamovirus – the genus that bears other economically important and contagious pathogens that infect Solanaceae, such as Tobacco mosaic virus (TMV) and Tomato mosaic virus (ToMV). ToBRFV was initially isolated from tomato plants grown in greenhouses in Jordan in 2015 (Salem et al., 2016).  Prior to this, in 2014, an outbreak of a new disease infecting resistant tomato cultivars grown in net houses was observed in Southern Israel and was determined to be caused by the Israeli isolate of ToBRFV with high genomic sequence identity to the Jordan isolate (Luria et al., 2017).  Most recently, ToBRFV was detected in tomato and chili pepper plants growing in nurseries in Yurecuaro, Michoacan, Mexico (NAPPO, 2018).  There have been no previous reports of ToBRFV from the USA. The recent detection in greenhouse tomato plants in California that subsequently resulted in the destruction of all infested plants, does not verify the establishment of ToBRFV in the country (see ‘Initiating Event’).

Tobamoviruses infecting tomato are of great concern, but ToBRFV is of special concern because of its ability to overcome resistance of the TM-22 resistance gene which is genetically bred into tomato plants for resistance against Tobamoviruses (Luria et al., 2017).  The Israeli isolate of ToBRFV was found to infect pepper (Capsicum annuum) plants harboring the L resistance genes, when cultivated in contaminated soil from previous grown infected tomato plants, especially in hot temperatures above 30°C (Luria et al., 2017).  Disease caused by ToBRFV is infectious and local spread can occur rapidly through mechanical means (see ‘Dispersal and spread’).

Hosts:  Tomato (Solanum lycopersicum) and pepper (Capsicum annuum) are the main hosts (Salem et al., 2016; Luria et al., 2017; NAPPO, 2018).  Petunia (Petunia hybrida) and certain weeds like black nightshade (S. nigrum) were shown to be asymptomatic hosts in experiments (Luria et al., 2017).

Symptoms:  The Jordan isolate of ToBRFV in tomato caused mild foliar symptoms and strong brown rugose symptoms on fruit thereby affecting market value of the crop.   Mechanically inoculated plants exhibited a range of local and systemic symptoms (Salem et al., 2016).  Symptoms caused by the Israeli isolate of ToBRFV were mild and severe mosaic of leaves with occasional narrowing of the leaves.  Yellow spots on fruit affected 10-15% of the total number of fruit produced on symptomatic plants (Luria et al., 2017).

In pepper plants cultivated in ToBRFV-contaminated soil from previously grown infected tomato plants, especially in temperatures above 30°C, the hypersensitivity response included necrotic lesions on roots and stems resulting in inhibited plant growth and possibly plant collapse.  Petunia and certain weeds are symptomless hosts, while eggplant and potatoes are non-hosts for the virus (Luria et al., 2017).

Dispersal and spread: ToBRFV is transmitted mechanically (plant to plant) via externally contaminated seed (over long distances), common cultural practices (worker’s hand, clothes), tools, equipment and circulating water (Salem et al., 2016).  Tobamoviruses are capable of preserving infectivity in seeds and contaminated soil (Broadbent, 1976; Luria et al., 2017).  Weed hosts can serve as reservoirs of inoculum for infection of the main hosts.

Damage Potential: Tobamoviruses are of main concern in tomato crops, especially when cultivated in protected environments such as greenhouses, where conditions favor rapid spread of the pathogen.  The ability of ToBRFV to break resistance in tomato plants harboring the TM-22 resistance gene and, under certain conditions also pepper plants harboring the L resistance genes, makes the potential for damage a main concern. The stability and infectious nature of this Tobamovirus via mechanical transmission by workers, tools and equipment during the handling of plants, with infection most likely occurring when seedlings are thinned in nurseries or transplanted, plus transmission through contaminated seed, soil and circulating water, render a high potential for damage in tomato and pepper.  Crop production and quality of ToBRFV-consumable tomato and pepper fruit can be affected thereby significantly impacting their market value.

Worldwide Distribution: Asia: Jordan (Salem et al., 2016), Israel (Luria et al., 2017); North America: Mexico (NAPPO, 2018).

Official Control: None reported.

California Distribution: Tomato brown rugose fruit virus is not present in California.  The detection of ToBRFV in greenhouse tomato plants in Santa Barbara County resulted in the destruction of the plants (see ‘Initiating Event’).

California Interceptions: None reported.

The risk Tomato brown rugose fruit virus would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: It is likely that Tomato brown rugose fruit virus can establish a widespread distribution in California wherever tomato and pepper plants are cultivated.

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: The main hosts of ToBRFV are tomato and pepper cultivars.  Experimentally, petunia and few weeds have been proven to be asymptomatic hosts and weeds may serve as reservoirs of inoculum for subsequent infections of main cultivated hosts.

Evaluate the host range of the pest.

Score: 1

Low (1) has a very limited host range.

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

3) Pest Dispersal Potential: Tomato brown rugose fruit virus is a stable and readily infectious virus plant pathogen. It is easily transmitted from plant to plant by mechanical means which include common cultural practices, contaminated tools, equipment, hands, clothes, soil, and infected plants, and seed. Infections most likely occur in protected environments, where favorable conditions for pathogen spread exist, as when seedlings are thinned in nurseries or transplanted. Transmission of ToBRFV by insect vectors has not been reported.

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: ToBRFV can break resistance in tomato plants harboring the TM-22 resistance gene and under certain conditions, also pepper plants harboring the L resistance genes. The stability and infectious nature of this Tobamovirus render a high potential for damage in tomato and pepper particularly under protected environments such as greenhouses.  Crop production and quality of ToBRFV consumable tomato and pepper fruit can be affected thereby significantly impacting their market value.

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

Economic Impact: A, B, C, D, G.

A. The pest could lower crop yield.

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

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

D. The pest could negatively change normal cultural practices.

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

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

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

Economic Impact Score: 3

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

– Medium (2) causes 2 of these impacts.

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

5) Environmental Impact: The natural host range is limited to tomato and pepper which are cultivated crops.  Home/urban gardening of these host plants may be impacted if infected with ToBRFV. Consequently, the establishment of this resistance-breaking Tobamovirus species in California could trigger additional official or private 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 Tomato brown rugose fruit virus:

Add up the total score and include it here. 13

-Low = 5-8 points

-Medium = 9-12 points

High = 13-15 points

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

Evaluation is ‘0’.  ToBRFV is not established in California.

Score: 0

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

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

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

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

Final Score:

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

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

Uncertainty:  

The potential for weed plants, especially those commonly found in tomato and pepper fields in California, to serve as hosts and inoculum reservoirs of the pathogen is not known.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Tomato brown rugose fruit virus is A.


References:

Broadbent, L.  1976.  Epidemiology and control of Tomato mosaic virus.  Annual Review of Phytopathology, 14:75-96.

Luria, N. Smith, E., Reingold, V., Bekelman, I., Lapidot, M., Levin, I., Elad, N., Tam., Y., Sela, Abu-Ras, A., Ezra, N., Haberman, A., Yitzhak, L., Lachman, O. and Dombrovsky, A.  2017.  A new Israeli Tobamovirus isolate infects tomato plants harboring Tm-22 resistance genes.  PLoS ONE 12 (1):e0170429.  doi:10.1371/journal.pone.0170429

NAPPO. 2018. Tomato Brown Rugose Fruit Virus: detected in the municipality of Yurecuaro, Michoacan. North American Plant Protection Organization (NAPPO) Phytosanitary Alert System.  September 17, 2018. https://www.pestalerts.org/oprDetail.cfm?oprID=765.

Salem, N., Mansour, A., Ciuffo, M., Falk, B. W., and Turina, M.  2016.  A new Tobamovirus infecting tomato crops in Jordan.  Archives of Virology, 161:503-506.


Responsible Party:

John J. Chitambar, Primary Plant Pathologist/Nematologist, California Department of Food and Agriculture, 3294 Meadowview Road, Sacramento, CA 95832. Phone: 916-738-6693, plant.health[@]cdfa.ca.gov.


Comment Period:* CLOSED

11/07/18 – 12/22/18


*NOTE:

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


Comment Format:

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

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

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

♦  Comments may not be posted if they:

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

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

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: A


Posted by ls 

Cercospora insulana Sacc. 1915

California Pest Rating for
Cercospora insulana Sacc. 1915
Pest Rating: C

PEST RATING PROFILE

Initiating Event: 

On May 11, 2018 a postal shipment of statice dried flowers showing symptoms of leaf spots was intercepted by the CDFA at a Federal Express (FedEx) office.  The shipment was destined to a private owner in Alameda County and had originated in Hawaii.  A sample of the symptomatic flowers was sent to the CDFA Plant Pathology Lab for disease diagnoses.  On May 17, 2018 Cheryl Blomquist, CDFA plant pathologist, identified the fungus, Cercospora insulana associated with the leaf spots.  The present status and rating of C. insulana is reevaluated here.

History & Status:

Background:  Cercospora insulana is a fungal plant pathogen in the Mycosphaerellaceae family, that causes leaf spot of statice and other host plants.

The pathogen is globally widespread.  In the USA, Cercospora insulana has only been reported from Florida and California (Farr & Rossman, 2018).  In California, prior to its most recent detection, the pathogen has been reported on Armeria sp. and Limonium spp. in northern and southern coastal region of California (French, 1989).

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

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

Hosts: Armeria sp., A. maritima (thrift seapink), Limonium sp., L. bonducellii (Algerian statice), L. californicum (California sea lavender/marsh rosemary), L. gmelinii (syn. Statice gmelinii; Siberian statice), L. sinuatum (syn. Statice sinuata; statice/wavyleaf sea lavender), L. vulgare (common sea lavender) (CABI, 2018; French, 1989); Nerium indicum (Indian oleander) (XueWen et al., 2017)

Symptoms:  Leaf spot symptoms caused by Cercospora insulana in field-grown statice were reported from Italy as circular, brown lesions with a darker edge, 3-6 mm in diameter and surrounded by an orange or reddish halo.  Old lesions enlarged and coalesced, causing yellowing and senescence of leaves.  Heavy infections resulted in severe defoliation and retarded growth or death in panicles. Lesions were also present on the wings of the flower scapes, while scapes proper were not involved (Nicoletti et al., 2003).

Damage Potential: Quantitative losses due to Cercospora insulana have not been reported.  If left uncontrolled, leaf spotting may lead to disease outbreaks under favorable conditions, wherein photosynthetic areas can be reduced.  Heavy infections may result in severe defoliation, retarded plant growth and death of flowers in statice, and likely, in other ornamental host plants.  Nursery productions of ornamental hosts under controlled and conducive conditions for pathogen development would also be of concern in California.  However, damage potential due to this pathogen is likely to be similar to other Cercospora diseases which is usually low (Agrios, 2005).  Furthermore, fungicide applications and sanitary measures including the use of clean seed have been used to successfully control Cercospora diseases (Agrios, 2005).

Worldwide Distribution: Asia: China (XueWen et al., 2017), India, Myanmar; Africa: Kenya, Malta, South Africa, Zimbabwe; Europe: Caucasus, Italy, Portugal, Russia: North America: USA (California, Florida), Haiti; Oceania: Australia, New Zealand (Farr & Rossman, 2018)

Official Control: Presently, Cercospora insulana is on the ‘Harmful Organism’ list for Brazil, Colombia, Ecuador and Israel (USDA PCIT, 2018).

California Distribution:  Cercospora insulana is distributed in northern and southern coastal areas of the State (French, 1989).

California Interceptions To date, the recent detection of C. insulana (see ‘initiating event’) has been the only interception reported.

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

Consequences of Introduction: 

1) Climate/Host Interaction: Cercospora insulana has only been detected in northern and southern coastal regions in California. These limited regions provide adequate moisture that favor development of the pathogen in host plants like statice.

Evaluate if the pest would have suitable hosts and climate to establish in California.  Score: 2

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

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

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

2) Known Pest Host Range: The known host range is limited to statice, thrift seapink and Indian oleander in the genera Limonium, Armeria and Neria.

Evaluate the host range of the pest. Score: 1

Low (1) has a very limited host range.

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

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

Evaluate the natural and artificial dispersal potential of the pest.

Score: 3

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

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

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

4) Economic Impact: Quantitative losses due to Cercospora insulana have not been reported. However, for nurseries particularly, infected host plants with leaf spots could result in lowered value resulting in use of fungicidal treatments thereby increasing production costs, and loss of markets.

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

Economic Impact: B, C

A. The pest could lower crop yield.

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

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

D. The pest could negatively change normal cultural practices.

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

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

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

Economic Impact Score: 2

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

Medium (2) causes 2 of these impacts.

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

5) Environmental Impact: Home garden plantings of statice species may be impacted if the pathogen was to establish under favorable environmental conditions and in the absence of adequate disease control.  The pathogen has not been detected in oleander in California.

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

Environment Impact: E 

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

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

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

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

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

Environmental Impact Score: 2

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

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

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

Consequences of Introduction to California for Cercospora insulana:

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

-Low = 5-8 points

Medium = 9-12 points

-High = 13-15 points

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

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

Evaluation is ‘Medium’ in California.

Score: (-2)

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

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

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

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

Final Score:

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

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

Uncertainty:  

None.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Cercospora insulana is to continue as C.


References:

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

Farr, D.F., & A. Y. Rossman.  2016.  Fungal Databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA.  Retrieved May 18, 2018, from http://nt.ars-grin.gov/fungaldatabases/

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

Nicoletti, R., F. Raimo, C. Pasini, and F. D’Aquila.  2003.  Occurrence of Cercospora insulana on statice (Limonium sinuatum) in Italy.  Plant Pathology 52: 418.  DOI: 10.1046/j.1365-3059.2003.00840.x

USDA PCIT.  2018.  USDA Phytosanitary Certificate Issuance & Tracking System. Retrieved May 18, 2018. 12:45:06 pm CDT.  https://pcit.aphis.usda.gov/PExD/faces/ReportHarmOrgs.jsp.

XueWen, X., Z. Qian and G. YingLan.  2017.  New records of Cercospora and Pseudocercospora in China.  Mycosystema 36: 1164-1167.


Responsible Party:

John J. Chitambar, Primary Plant Pathologist/Nematologist, California Department of Food and Agriculture, 3294 Meadowview Road, Sacramento, CA 95832. Phone: 916-738-6693, plant.health[@]cdfa.ca.gov.


Comment Period:* CLOSED

9/13/18 – 10/28/18


*NOTE:

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


Comment Format:

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

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

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Pest Rating: C


Posted by ls 

Citrus Viroid V

California Pest Rating  for
Citrus viroid V
Pest Rating: B

PEST RATING PROFILE

Initiating Event:  

The risk of infestation of Citrus viroid V (CVd-V) in California is evaluated and a permanent rating is herein proposed. 

History & Status:

Background: The origin of Citrus viroid V (CVd-V) is uncertain (Serra et al., 2008a).  In a study in Spain on the response of Citrus species and citrus-related genera to viroid infections, Serra and other researchers (2008a) originally detected CVd-V in Atalantia citroides, a citrus relative plant propagated on rough lemon rootstock and graft-inoculated with artificial mixtures of different viroids.  The viroid source was provided to them by a researcher at the University of California, Riverside and purified preparations were shown to be infectious in Etrog citron (Citrus medica), a classical indicator plant of citrus viroids.  Subsequently, CVd-V was considered a new species of the genus Apscaviroid in the family Pospiviroidae (Serra et al., 2008a).  Viroids are classified within two families: Pospiviroidae and Avsunviroidae.  Citrus are natural hosts of several viroid species that belong to the family Pospiviroidae.  Therefore, A. citroides was identified as an unusual viroid host since it was resistant to all previously known citrus viroids, yet capable of replicating CVd-V (Serra et al., 2008b).  Infectious assays conducted by Sierra et al. (2008) showed that CVd-V in Etrog citron exhibited mild symptoms, however, co-infections with either Citrus bent leaf viroid (CBLVd) or Citrus dwarfing viroid (CDVd, previously Citrus viroid III), also belonging to the genus Apscaviroid, showed synergistic effects in contrast to single infections of CVd-V or the other two viroids, however, titers of the viroids remained the same in singly or doubly infected plants (Serra et al., 2008a).

While the origin of CVd-V is not known, Pakistan may be one of the geographic origins of the viroid (Serra et al., 2008a, b; Parakh et al., 2017).  Serra et al. (2008a) suggested that the viroid was present, but overlooked or unnoticed, in field sources containing Hop stunt Viroid or Citrus dwarfing viroid – both of which have electrophoretic mobilities similar to CVd-V.  CVd-V has been found with some variations in its nucleotide sequence, in several countries in Africa, Asia, Europe, and North America (see ‘Worldwide Distribution).

In June 2016, the Citrus Clonal Protection Program-National Clean Plant Network (CCPP-NCPN), University of California, Riverside, California detected Citrus Viroid V in citrus budwood samples submitted by the CDFA for virus and viroid testing under the mandatory California (CA 3701) Citrus Nursery Stock Pest Cleanliness Program.  These budwood samples were taken from asymptomatic redblush grapefruit (Citrus paradisi) and variegated calamondin (C. madurensis) from a nursery in Tulare County.  This find marked the natural occurrence of CVd-V in California and corroborated the earlier report of CVd-VCA variant in the State (Dang et al., 2018; Serra et al., 2008b).

Hosts: Citrus spp.  including ‘Sanguinelli’, Salustiana’, and ‘Ricart navelina’ sweet oranges (Citrus x sinensis),  ‘Oroval’ and ‘Hernandina clementines (C. clementina), ‘Fino’ and ‘Verna’ lemons (C. limon), ‘Sevilano’ and ‘Cajel’ sour orange (C. aurantium), ‘Clausellina’ satsuma (C. unshiu), Temple mandarin (C. temple), Tahiti lime, Palestine sweet lime (C. limettioides), calamondin (C. madurensis), ‘Calabria’ bergamot (C. bergamia), ‘Orlando’ tangelo (C. paradisi x C. tangerina), ‘Page’ mandarin [(C. paradisi x C. tangerina) x C. clementina], and ‘Nagami’ kumquat (Fortunella margarita),  and Etrog citrus (Atlantia citroides) (Serra et al., 2008); ‘Shiranui’ [(C. unshiu x C. sinensis) x C. reticulata] (Ito and Ohta, 2010); ‘Moro blood’ sweet orange (Citrus x sinensis) (Bani Hashemian et al., 2013); redblush grapefruit (C. paradisi) (Dang et al., 2018).

Symptoms:   Citrus viroid V induced mild characteristic symptoms of very small necrotic lesions and cracks, sometimes filled with gum, in the stems of the viroid indicator plant, Etrog citron.  However, CVd-V reacted synergistically when Etrog citrus was co-infected with either citrus bent leaf viroid (CBLVd) or Citrus dwarfing viroid (CDVd), and showed severe stunting and epinasty with multiple lesions in the midvein.  Plants co-infected with CBLVd and CVd-V exhibited severe stem cracking characteristic of CBLVd, but without gum exudates, whereas plant co-infected with CDVd showed necrotic lesions (Serra et al., 2008a). Symptoms induced by CVd-V alone in commercial species and varieties are presently not known since commercial trees may be co-infected with several viroids (Ito and Ohta, 2010; Serra et al., 2008a).  Citrus viroid V may be present in asymptomatic citrus plant tissue – as recently evidenced by its detection in asymptomatic budwood collected from Tulare County, California.

Damage Potential:  The effect of CVd-V in commercial citrus rootstock-scion combinations, alone and in combination with other viroids, is yet unknown, however, Serra et al. (2008b) suggested that CVd-V could reduce tree size and yield as has been reported for clementine trees grafted on trifoliate orange co-infected with several viroids. Therefore, the need for nursery planting stock free of CVd-V is important.

Transmission:  Similar to other citrus viroids, CVd-V is graft-transmitted and is spread mainly through the propagation of infested material.

Worldwide Distribution:  Africa: Oman (Serra et al., 2008), Tunisia (Hamdi et al., 2015); Asia: China, Japan, Nepal, Pakistan (Cao et al., 2013), Iran (Bani Hashemian et al., 2010), Turkey (Önelge and Yurtmen, 2012); Europe: Spain (Serra et al., 2008); North America: USA (Serra et al., 2008).

Official Control: Citrus viroid V is a disease agent of concern that is tested for in the CDFA Citrus Nursery Stock Pest Cleanliness Program (3 CCR §§ 3701, et seq.).

California Distribution Tulare County (Dang et al., 2018).

California Interceptions: None reported.

The risk Citrus viroid V would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: Citrus viroid V is likely to establish within infested propagative citrus materials in all citrus-growing regions of 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: Citrus viroid V has a moderate host range that is limited to several species and varieties of Citrus.

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: Citrus viroid V replicates autonomously within infested plants and is spread mainly through the propagation and movement of infested planting materials to non-infested regions.

Evaluate the natural and artificial dispersal potential of the pest.

Score: 2

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

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

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

4) Economic Impact: The effect of CVd-V in commercial citrus rootstock-scion combinations, alone and in combination with other viroids, is yet unknown, however, it has been suggested by Serra et al. (2008b) that CVd-V could reduce tree size and yield.

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

Score: A, B, C

A. The pest could lower crop yield.

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

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

D. The pest could negatively change normal cultural practices.

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

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

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

Economic Impact Score: 3

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

– Medium (2) causes 2 of these impacts.

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

5) Environmental Impact: It is probable that home, urban, public garden and landscape plantings of CVd-V-infested citrus plantings may be significantly impacted by the viroid singly or in combination with other viroids.

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

Environmental Impact: E

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

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

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

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

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

Environmental Impact Score: 2

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

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

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

Consequences of Introduction to California for Citrus Viroid V

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 CVd-V 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)Currently, Citrus viroid V has only been detected in a nursery in Tulare County.

Final Score:

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

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

Uncertainty: 

The effect of CVd-V in commercial citrus rootstock-scion combinations, alone and in combination with other viroids, is yet unknown.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Citrus viroid V is B.


References:

Bani Hashemian, SM, Taheri, H, Duran-Vila, N, and Serr, P.  2010.  First report of Citrus viroid V in Moro blood sweet orange in Iran.  Plant Disease 94: 129.

Cao, M. J., Liu, Y. Q., Wang, X. F., Yang, F. Y., and Zhou, C. Y.  2010.  First report of Citrus bark cracking viroid and Citrus viroid V infecting Citrus in China.  Plant Disease 94: 922. https://doi.org/10.1094/PDIS-94-7-0922C

Dang, T., Tan, S. H., Bodaghi, S., Greer, G., Lavagi, I., Osman, F., Ramirez, B., Kress, J., Goodson, T., Weber, K., Zhang, Y. P., Vidalakis, G.  First report of Citrus Viroid V naturally infecting grapefruit and calamondin trees in California.  Plant Disease, Posted online on August 10, 2018. https://doi.org/10.1094/PDIS-01-18-0100-PDN

Hamdi, I., Elleuch, A., Bessaies, N., Grubb, C. D., and Fakhfakh, H. 2015. First report of Citrus viroid V in North Africa. Journal of General Plant Pathology 81, 87

Ito, T., and Ohta, S.  2010.  First report of Citrus viroid V in Japan.  Journal of General Plant Pathology 76: 348-350.

Önelge, N., and Yurtmen, M. 2012. First report of Citrus viroid V in Turkey. Journal of Plant Patholology 94 (Suppl. 4), 88.

Parakh, D. B., Zhu, S., and Sano, T.  2017.  Geographical distribution of viroids in South, Southeast, and East Asia.  In: Apscaviroids Infecting Citrus Trees by Tessitori, M, Viroids and Satellites, Edited by Hadidi, A, Flores, R, Randles, JW, and Palukaitis, P, Academic Press Ltd-Elsevier Science Ltd, Pages 243-249

Serra, P., Barbosa, C. J, Daros, J. A., Flores, R., Duran-Vila, N. 2008a. Citrus viroid V: molecular characterization and synergistic interactions with other members of the genus Apscaviroid. Virology 370, 102112.

Serra, P., Eiras, M., Bani-Hashemian, S. M., Murcia, N., Kitajima, E.W., Daro`s, J. A., et al., 2008b. Citrus viroid V: occurrence, host range, diagnosis, and identification of new variants. Phytopathology 98, 11991204.


Responsible Party:

John J. Chitambar, Primary Plant Pathologist/Nematologist, California Department of Food and Agriculture, 3294 Meadowview Road, Sacramento, CA 95832. Phone: 916-738-6693, plant.health[@]cdfa.ca.gov.


Comment Period:* CLOSED

9/13/18 – 10/28/18


*NOTE:

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♦  Comments may not be posted if they:

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Pest Rating: B


Posted by ls 

Corynespora cassiicola (Berk. & M. A. Curtis) C. T. Wei 1950

California Pest Rating for
Corynespora cassiicola (Berk. & M. A. Curtis) C. T. Wei 1950
Pest Rating: B

 


PEST RATING PROFILE

Initiating Event: 

On September 27, 2017, a shipment of desert rose (Adenium obesum) plants showing symptoms of leaf spot disease was intercepted by San Diego Agricultural County inspectors.  The shipment had originated in Florida and was destined to a private company in San Diego County.  A sample of symptomatic plant leaves was collected by the San Diego Agriculture County and sent to the CDFA Plant Pathology Laboratory in Sacramento.  On October 18, 2017, the fungus, Corynespora cassiicola, was identified by CDFA plant pathologist, Suzanne Latham, to be associated with the leaf spot symptoms. A temporary ‘Q’ rating was assigned to the pathogen and consequently, the shipment was destroyed.  Corynespora cassiicola was previously detected on May 7, 2008, in an intercepted shipment of Mandevilla plants that originated in Florida and was destined to a nursery in San Diego County.  This detection marked the first report of the pathogen in California and resulted in the destruction of the shipment.  The current rating and consequences of introduction of C. cassiicola in California are assessed here and a permanent rating is proposed.

History & Status:

Background:  Corynespora cassiicola is a fungal plant pathogen that attacks a wide range of plants from tropical and subtropical countries causing leaf spot disease in several economically important crops under different common names such as Corynespora leaf spot of cucumber and several other hosts, blotch disease of cucurbits, stem and fruit spot of eggplant, papaya and target spot of tomato and cotton.  The fungus has been found in plant leaves, stems, fruit, roots, nematode cysts, and human skin and comprises many isolates.  Majority of isolates reported have been obtained from lesions or from fulfilled Koch postulate trials and are known to be plant pathogens.  However, isolates have also been reported from dead organic matter and non-symptomatic plant tissue and some can be both depending on the host substrate (Dixon et al., 2009).  Isolates may vary in virulence in host specificity.  Some isolates that specifically parasitize weed hosts without affecting agricultural crops may serve as potential bioherbicides agents (Smith & Schlub, 2005).  In South-east Asia, C. cassiicola causes leaf fall disease of rubber, which is one of the most serious leaf diseases of rubber in that region.

The pathogen was first described as Helminthosporium cassiicola by Berkeley and Curtis in 1868, and subsequently underwent several taxonomic changes to now be known as Corynespora cassiicola (Farr & Rossman, 2018). This pathogen is ubiquitous and has been reported to cause major economic losses in more than 70 countries (Dixon et al., 2009).

Disease cycle:  The pathogen survives in infested plant materials for more than two years.  High humidity, warm temperature (25-32°C) and long days are necessary for conidia production, infection and disease development.  Fluctuating day and night temperatures favor disease development (Williams, 1996).  The disease develops in tomatoes at favorable temperatures of 20-28°C and infection can occur at 16-32°C.  Extended periods of 16 to 44 hours of high moisture are necessary for optimum disease development (Pernezney et al., 2014).

Dispersal and spread: Infested planting stock, plant material, plant debris.  Conidia (spores) are airborne and seedborne (Daughtrey et al., 1995).

Hosts: More than 530 plant species from 380 genera including monocots, dicots, ferns, and one cycad have been reported to support growth of C. cassiicola (Dixon et al., 2009). Economically important host crops for California include Cucumis sativus (cucumber), Cucurbita moschata (pumpkin), C. moschata (pumpkin), C. pepo (marrow), cucurbits, Gossypium sp. (cotton), Solanum lycopersicum (tomato), S. melongena (eggplant) and ornamentals (CABI, 2018; Farr & Rossman, 2018).  Ornamental hosts include Aeschyanthus pulcher (lipstick vine), Aphelandra squarrosa (zebra plant), Catharnathus roseus (Madagascar periwinkle), Begonia, Hydrangea macrophylla (bigleaf hydrangea), Euphorbia pulcherrima (poinsettia), Saintpaulia ionantha (African violet) and Salvia splendens (scarlet sage) (Daughtrey et al., 1995)

Symptoms:  The initial symptoms of target spot in tomato are pinpoint-size, water-soaked lesions on the upper surfaces of leaves. These lesions increase in size, turn circular and pale brown with individual yellow halos.  Over time lesions coalesce and tissue may collapse while the leaflet remains attached to the petiole. Similar lesions may develop on petioles and stems resulting in rapid collapse of affected leaflets.  Lesions can develop on young fruit and resemble those caused by abiotic factors. These lesions are initially dark, sunken, pinpoint and brown and may later develop into craters. On ripe fruit, large, circular lesions develop with pale brown centers that crack and over time create avenues for secondary invading pathogens (Pernezny et al., 2014).  In infected cucurbits, initial lesions are angular yellow spots with light brown centers and dark brown borders.  As these lesion age, they drop out. Young and green fruit are not susceptible however, early infection of the blossom end of fruit may result in shriveling and darkening of the infected area with dark sporulation (Williams, 1996).  On ornamental plants such as poinsettia, lesions may be irregular, large and brown on bracts and primarily at the tips and margins of leaves; on hydrangea lesions may be small, reddish purple, circular with tan centers and reddish-purple margins; on African violets lesions are irregular and brown (Daughtrey et al., 1995).

Damage Potential: In the USA, reports of losses from target spot of field tomatoes are restricted to the Southeast which is frequented with high humidity and warm temperature climate (Pernezny et al., 2014). In California, if left uncontrolled, Corynespora disease development is likely to occur in greenhouses under favorable temperature and high humidity conditions. Impact of disease caused by this pathogen may be mitigated through proper sanitation, use of resistant varieties and regular applications of fungicidal treatments.

Worldwide Distribution: Asia: Bangladesh, Brunei Darussalam, Cambodia, China, India, Indonesia, Japan, Republic of Korea, Laos, Malaysia, Maldives, Myanmar, Nepal, Pakistan, Philippines, Singapore, Sri Lanka, Taiwan, Thailand, Vietnam, Yemen; Africa: Benin, Cameroon, Congo, Democratic Republic of Congo, Côte d’Ivoire, Egypt, Ethiopia, Gabon, Ghana, Guinea, Liberia, Mauritius, Nigeria, Seychelles, Sierra Leone, South Africa, Sudan, Tanzania, Togo, Uganda, Zambia; Central America and Caribbean:  Antigua and Barbuda, Barbados, Belize, British Virgin Islands, Costa Rica, Cuba, Dominica, El Salvador, Guadeloupe, Guatemala, Haiti, Honduras, Jamaica, Nicaragua, Puerto Rico, Trinidad and Tobago, United States Virgin Islands; Europe: Austria, Bulgaria, Denmark, France, Germany, Hungary, Italy, Netherlands, Norway, Romania, Russian Federation, United Kingdom, Ukraine; North America: Canada, Mexico, USA; Oceania: American Samoa, Australia, Fiji, Guam, Micronesia, New Zealand, northern Mariana Islands, Palau, Papua New Guinea, Samoa, Solomon Islands, Vanuatu; South America: Argentina, Bolivia, Brazil, Colombia, Ecuador, French Guiana, Guyana, Venezuela (CABI, 2018).

In the United States, C. cassiicola has been reported from Alabama, Florida, Hawaii, Illinois, Iowa, Louisiana, Minnesota, Mississippi, Nebraska, New York, North Carolina, North Dakota, South Carolina, Tennessee, Virginia, and Wisconsin (CABI, 2018).

Official Control: Corynespora cassiicola is on the ‘Harmful Organism Lists” for Israel, Namibia, South Africa and Vietnam (USDA PCIT, 2018).

California Distribution: Corynespora cassiicola has not been reported from California.  The pathogen is not known to be established in California.

California Interceptions:  There have been two interceptions of plants infected with Corynespora cassiicola (see: ‘Initiating Event’).

The risk Corynespora cassiicola would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: Corynespora cassiicola requires prolonged periods of high humidity (16-44 hours) and warm temperature (25-32°C) for disease development. These climatic conditions would limit the ability of the pathogen to establish and spread within California.

Evaluate if the pest would have suitable hosts and climate to establish in California.  Score: 1

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

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

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

2) Known Pest Host Range: The pathogen has a very wide and diverse host range that comprises more than 530 plant species from 380 genera including monocots, dicots, ferns, and one cycad. Economically important host crops for California include cucurbits, cotton, tomato, eggplant and ornamentals.

Evaluate the host range of the pest.

Score: 3

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

– Medium (2) has a moderate host range.

High (3) has a wide host range.

3) Pest Dispersal Potential: Conidia are produced in abundance and are dispersed by air currents, infected seeds, host plant material and debris. Therefore, a high score is given to this category.

Evaluate the natural and artificial dispersal potential of the pest.

Score: 3

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

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

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

4) Economic Impact: Plant damage caused by cassiicola is more likely under prolonged periods of high humidity and warm temperatures found in greenhouse cultivation than in open field environments of the state. If left uncontrolled, infections by the pathogen could result in lower crop yield and value resulting in the loss of markets. However, the administration of proper control measures may mitigate impact of damage caused by this pathogen.  Therefore, a medium score is given to this category.

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

Economic Impact: A, B

A. The pest could lower crop yield.

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

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

D. The pest could negatively change normal cultural practices.

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

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

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

Economic Impact Score: 2

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

Medium (2) causes 2 of these impacts.

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

5) Environmental Impact:  No significant impact to the environment is likely as the requirements of prolonged, high humidity and warm temperatures would considerably limit the ability of cassiicola to establish within the state.  

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

Environment Impact:  None

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

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

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

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

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

Environmental Impact Score: 1

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

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

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

Consequences of Introduction to California for Corynespora cassiicola:

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

-Low = 5-8 points

Medium = 9-12 points

-High = 13-15 points

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

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

Evaluation is ‘Not established’ in California and has only been detected in intercepted plant shipments to the State.

Score: (0)

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

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

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

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

Final Score

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

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

Uncertainty:

None.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Corynespora cassiicola is B.


References:

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

Daughtrey, M. L., Wick, R. L., and Peterson, J. L.  1995.Corynespora leaf spot of Catharanthus, Hydrangea, Poinsettia, and SaintpauliaIn, Compendium of Flowering Potted Plant Diseases. APS Press, The American Phytopathological Society 90p.

Dixon, L. J., Schlub, R. L., Pernezny, K., and Datnoff, L. E.  2009.  Host specialization and phylogenetic diversity of Corynespora cassiicola.  Phytopathology 99: 1015-1027.

Farr, D.F., and Rossman, A. Y.  2016.  Fungal Databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA.  Retrieved August 1, 2016, from http://nt.ars-grin.gov/fungaldatabases/

Pernezny, K. L., Blazquez, C. H., Smith, L. J., and Schlub, R. L.  2014).  Target spot.  In, Compendium of Tomato Disease and Pests Second Edition, Edited by J. B. Jones, T. A. Zitter, T. M. Momol, and S. A. Miller. 44-46p.

Smith, L. J., and Schlub, R. L. 2005. Foliar fungi on weeds of Guam and the potential for Corynespora cassiicola as a bioherbicide for   Stachytarpheta jamaicensis. (Abstr.) Phytopathology 95: S93.

USDA PCIT.  2017.  USDA Phytosanitary Certificate Issuance & Tracking System. Retrieved May 23, 2018. 11:53:45 am CDT.  https://pcit.aphis.usda.gov/PExD/faces/ReportHarmOrgs.jsp.

Williams, P. H.  1996.  Target leaf spot.  In, Compendium of Cucurbit Diseases, Ed. T. A. Zitter, D. L. Hopkins, and C. E. Thomas.  APS Press, The American Phytopathological Society p 31-32.


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 Period:* CLOSED

5/31/18 – 7/15/18


*NOTE:

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


Comment Format:

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

Example Comment:
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♦  Comments may not be posted if they:

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

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Pest Rating: B

 


Posted by ls 

 

 

Grapevine Pinot gris Virus (GPGV)

California Pest Rating  for
Grapevine Pinot gris Virus (GPGV)
Pest Rating: B

 


PEST RATING PROFILE

Initiating Event:   

A pest risk assessment and rating for Grapevine pinot gris virus (GPGV) was recently requested by Joshua Kress, CDFA Pest Exclusion Branch, in response to notification received on January 24, 2018, from Foundation Plant Service (FPS), on the detection of GPGV in their Foundation grapevine plants.  The risk of infestation of GPGV in California is evaluated and a permanent rating is herein proposed. 

History & Status:

Background: Although symptoms of stunting, chlorotic mottling, and leaf deformation had been observed on V. vinifera ‘Pinot gris’, in Trentino, North Italy since 2003, it was not until 2012 that Grapevine pinot gris was first detected by deep sequencing in one symptomatic and one symptomless grapevine, Vitis vinifera cv. Pinot gris in Northern Italy. In this initial study, GPGV was associated with field symptoms of chlorotic mottling and leaf deformation, reduced yield and low quality of berries, however the plant was also associated with several other viruses and viroids.  Furthermore, since GPGV was found in both symptomatic and symptomless plants from three different grape cultivars in a limited field survey, the virus could not be directly associated with the observed symptoms (Giampetruzzi et al., 2012; Glasa et al., 2014). This was further confirmed by Saldarelli et al. (2013) who reported 70% of GPGV-infected asymptomatic veins in cultivars Traminer and Pinot gris vineyards in Italy.  Bianchi et al. (2015) also detected GPGV in symptomatic and asymptomatic plants over a 3-year period in a field survey of productive vineyards and scion mother plant nurseries in Italy, however, the mean quantity of the virus was significantly higher in symptomatic vines than in asymptomatic plants. Consequently, a critical level or quantity of virus could not be associated with symptom expression.  Scientists in Italy determined that GPGV isolates that produce symptoms can be genetically differentiated from those that are asymptomatic (Saldarelli et al., 2015).

Grapevine pinot gris virus belongs to the genus Trichovirus in the family Betaflexiviridae.  Its full-length sequence was described and shown to be phylogenetically closely related to, yet molecularly different from Grapevine berry inner necrosis virus, another Trichovirus which was found in Japan and is transmitted by eriophyid mites (Giampetruzzi et al., 2012).  Since its original description in Italy, GPGV has been detected from symptomatic and asymptomatic grapevine cultivars in several countries in Europe and Asia, and few in North America, South America and Australia (see: ‘Worldwide Distribution’).

Grapevine Pinot gris virus (GPGV) was detected in California grapevine in Napa Valley and diagnosed by a testing service lab in Yolo County.  An informal report of this detection was made in 2015 (Rieger, 2015) and in a ‘list of pathogens report’ submitted by a testing service lab to the CDFA.  A formal first report of GPGV infecting grapevine was made in 2016 (Rwahnih et al., 2016) and marked a first detection of GPGV in the United States.  In 2016, Rwahnih and other scientists at the Foundation Plant Services screened 2,014 vines, including 23 vines of Pinot gris for the possible presence and prevalence of GPGV in the collections of FPS, which are the source of all certified grapevine plants produced in California.  Of all the vines tested, only one relatively rare, asymptomatic vine variety ‘Touriga Nacional” was found positive for GPGV. This vine had been imported from Portugal in 1981.  The risk of GPGV spread in commercial vineyards was considered low, given the very low prevalence of the pathogen in the FPS collection, however, the need for a large-scale survey of commercial vineyards in California was emphasized, as well as, the need for research to evaluate the effect of the virus on grapevine performance and wine quality.  Since cv ‘Touriga Nacional’ is rarely used in commercial vineyards, Angelini et al., (2016) molecularly surveyed 96 grapevine samples from four commercial wine grape vineyards in Napa Valley, California and reported the presence of GPGV in three cultivars, ‘Chardonnay’, ‘Cabernet Sauvignon’, and ‘Cabernet Franc’.

Grapevine pinot gris virus was recently detected in Foundation grapevine plants at FPS (see ‘Initiating Event’).  Subsequently, FPS removed all source vines from the Foundation vineyard and initiated monitoring of the site with additional testing implemented to detect and destroy any further detection and contain possible spread of the pathogen (personal communication: M. Al Rwahnih, Foundation Plant Services).

HostsGrapevine pinot gris virus has been found in at least 28 wine and table grape varieties of Vitis vinifera and hybrids. including Pinot gris, Pinot noir, Traminer, Chardonnay, Merlot, Chardonnay, Cabernet Franc, Cabernet Sauvignon, Carmenere Glera (Prosecco), Sauvignon Blanc and Shiraz (AWRI, 2018).

Symptoms:   Grapevines infected with GPGV may be symptomatic or asymptomatic.    Furthermore, specific symptoms caused by GPGV have been difficult to assign as GPGV-infected grapevines were infected with other viruses. Because of this, definitive symptoms have not been attributed to GPGV alone.  Symptoms putatively associated with GPGV include chlorotic mottling, leaf deformation, delayed bud-burst, stunted growth, reduced yields and low quality of berries with increased acidity (Saldarelli et al., 2015; AWRI, 2018).

Damage Potential:  The complete impact of GPGV on grapevine health is currently unknown and further research is need in this area (AWRI, 2018).  In Europe and Asia, GPGV and other concomitant viruses infesting grapevines have been associated with field observations of reduced yield, poor fruit set, poor quality and inner necrosis of berries (Giampetruzzi et al., 2012).  In Slovenia, the disease was reported to cause considerable economic losses (Mavrič Pleško et al., 2014).  Presently, the risk of spread of GPGV is considered low and the distribution of the virus has only been reported from commercial vineyards within Napa County (Al Rwahnih et al., 2016; Angelini et al., 2016).

TransmissionGrapevine Pinot gris virus is spread through movement of infected plant propagative material and by graft transmission.  There is the possibility of GPGV transmission by the eriophyid mite Colomerus vitus, like the other grapevine-infecting Trichovirus, Grapevine berry inner necrosis virus, however, this has not been confirmed.  Colomerus vitus commonly infests grapevine and has been reported in California.

Worldwide Distribution: Asia: China, South Korea, Georgia, Pakistan; Europe: Bosnia, Croatia, Czech Republic, France, Germany, Greece, Italy, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Turkey, Ukraine; North America: Canada, USA (California); South America: Brazil; Oceania: Australia. (Al Rwahnih et al., 2016; Angelini et al., 2016; Beuve et al., 2015; CABI, 2018; Casati et al., 2015; EPPO, 2018; Fan et al., 2016; Gazel et al., 2016; Lou et al., 2016; Mavrič Pleško et al., 2014; Rasool et al., 2017; Reynard, et al., 2016; Rius-Garcia & Olmos, 2017; Wu et al., 2017; Xiao et al., 2016).

Official Control: None reported.

California Distribution:  Napa County.

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

The risk Grapevine Pinot gris virus would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: Grapevine pinot gris virus is expected to be able to establish wherever wine and table grape varieties are cultivated in California, and therefore, is likely to establish a wide spread distribution.

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: Grapevine pinot gris virus has been found in at least 28 wine and table grape varieties of Vitis vinifera and hybrids. including Pinot gris, Pinot noir, Traminer, Chardonnay, Merlot, Chardonnay, Cabernet Franc, Cabernet Sauvignon, Carmenere Glera (Prosecco), Sauvignon Blanc and Shiraz. It’s known pest host range is evaluated as very limited.

Evaluate the host range of the pest.

Score: 1

Low (1) has a very limited host range.

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

3) Pest Dispersal Potential: GPGV is transmitted artificially through grafting and infested planting stock.  The involvement of a vector, an eriophyid mite Colomerus vitus, although likely, has not been confirmed. The virus has high reproduction within symptomatic and asymptomatic plants.  Therefore, a ‘High’ rating is given to this category.

Evaluate the natural and artificial dispersal potential of the pest.

Score: 3

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

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

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

4) Economic Impact: The economic impact of GPGV is not currently known and requires further research.  This is mainly due to evidence that the virus is present in both symptomatic and symptomless grape plants, and that other viruses and viroids may be present within the same plant infested by GPGV.  Nevertheless, putative symptoms of chlorotic mottling, leaf deformation, stunted growth, reduced yields and low quality of berries, have been associated with GPGV infestations.  This may relate to potentially lowering crop value and yield in production.  While the virus may be present in commercial vineyards of Chardonnay and Cabernet Sauvignon in California (Angelini et al., 2016), its risk of spread is considered low and its general impact on production is presently unknown.  Nursery production of grapevines may be affected.

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

Score: A, B

A. The pest could lower crop yield.

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

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

D. The pest could negatively change normal cultural practices.

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

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

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

Economic Impact Score: 2

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

Medium (2) causes 2 of these impacts.

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

5) Environmental Impact: No impact to the environment is expected.

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

Environmental Impact: None

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

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

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

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

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

Environmental Impact Score: 1

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

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

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

Consequences of Introduction to California for Grapevine Pinot gris 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 GPGV 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). Presently, Grapevine pinot gris virus has been reported only from Napa County.

Final Score

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

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

Uncertainty: 

Several aspects of Grapevine pinot gris virus are yet not known and require further research. In general, the impact of the virus on grape production, symptoms, prevalence and distribution within California are not fully known.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Grapevine Pinot gris virus is B.


References:

AWRI.  2018.  Grapevine pinot gris virus. Fact Sheet, Viticulture.  The Australian Wine Research Institute.  Updated February 2018.

Al Rwahnih, M., D. Golino, and A. Rowhani.  2016.  First report of Grapevine Pinot gris virus infecting grapevine in the United States.  Plant Disease (Posted online on March 4, 2016).  http://dx.doi.org/10.1094/PDIS-10-15-1235-PDN.

Angelini, E., N. Bertazzon, J. Montgomery, X. Wang, A. Zinkl, J. Stamp, and A. Wei.  2016.  Occurrence of Grapevine Pinot gris virus in commercial vineyards in the United States.  Plant Disease (Posted online on March 23, 2016): http://dx.doi.org/10.1094/PDIS-01-16-0055-PDN.

Beuve, M., T. Candresse, M. Tannières, and O. Lemaire.  2015.  First report of Grapevine Pinot gris virus (GPGV) in grapevine in France.  Plant Disease 99:293. http://dx.doi.org/10.1094/PDIS-10-14-1008-PDN.

Bianchi, G. L., F. De Amicis, L. De Sabbata, N. Di Bernardo, G. Governatori, F. Nonino, G. Prete, T. Marrazzo, S. Versolatto and C. Frausin.  2015.  Occurrence of Grapevine Pinot gris virus in Friuli Venezia Giulia (Italy): Field monitoring and virus quantification by real-time RT-PCR.  EPPO Bulletin 45:22-32.   DOI: 10.1111/epp.12196.

Casati, P., D. Maghradze, F. Ouaglino, A. Ravasio, O. Failla and P. A. Bianco.  First report of Grapevine pinot gris virus in Georgia.  Journal of Plant Pathology 1 (1). DOI: 10.4454/JPP.V98I1.003

EPPO.  2018.  Grapevine Pinot gris virus (GPGV00).  EPPO Global Database. https://gd.eppo.int/taxon/GPGV00/distribution

Fan, X. D., Y. F. Dong, Z. P. Zhang, F. Ren, G. J. Hu, Z.N. Li, and J. Zhou.  2016.  First report of Grapevine Pinot gris virus in Grapevines in China.  Plant Disease 100:540. http://dx.doi.org/10.1094/PDIS-08-15-0913-PDN.

Gazel, M., K. Caǧlayan, E. Elci, and L. Ozturk.  2016.  First Report of Grapevine Pinot gris virus in Grapevine in Turkey.  Plant Disease 100:657. http://dx.doi.org/10.1094/PDIS-05-15-0596-PDN.

Glasa, M., L. Predajňa, P. Komínek, A. Nagyová, T. Candresse and A. Olmos.  2014.  Molecular characterization of divergent grapevine Pinot gris virus isolated and their detection in Slovak and Czech grapevines.  Archives of Virology 159: 2103-2107.

Giampetruzzi, A., V. Roumia, R. Roberto, U. Malossinib, N. Yoshikawac, P. La Notte, F. Terlizzi, R. Credid, and P. Saldarelli.  A new grapevine virus discovered by deep sequencing of virus- and viroid-derived small RNAs in cv Pinot gris.  Virus Research 163:262-268.

Lou, B. H., Y. Q. Song, A. J. Chen, X. J. Bai, B. Wang, M. Z., Wang, P. Liu and J. J. He.  2016.  First report of Grapevine pinot gris virus in commercial grapevines in Southern China.  Journal of Plant Pathology 98: 677-697.

Mavrič Pleško, I., M. Viršček Marn, G. Seljak, and I. Žežlina.  2014.  First report of Grapevine Pinot gris virus infecting grapevine in Slovenia.  Plant Disease 98:1014.  http://dx.doi.org/10.1094/PDIS-11-13-1137-PDN.

Rasool, S., S. Naz, A. Rowhani, D. A. Golino, N. M. Westrick, K. D. Farrar and M. Al Rwahnih.  2017.  First report of Grapevine pinot gris virus infecting grapevine in Pakistan.  Plant Disease 101: 1958.

Rieger, T.  2015.  New grapevine virus detected in California: Grapevine Pinot Gris Virus discussed at UCD FPS meeting.  http://www.winebusiness.com/news/?go=getArticle&dataid=160912.

Reynard, J. -S, S. Schumacher, W. Menzel, J. Fuchs, P. Bohnert, M. Glasa, T. Wetzel and R. Fuchs.  2016.  First report of Grapevine pinot gris virus in German vineyards.  Plant Disease 100: 2545.

Ruiz-García, A. B., and A. Olmos.  2017.  First report of Grapevine pinot gris virus in Grapevine in Spain.  Plant Disease 101: 1070.

Saldarelli, P., A. Giampetruzzi, M. Morelli, U. Malossini, C. Pirolo, P. Bianchedi, and V. Gualandri.  2015.  Genetic variability of Grapevine Pinot gris virus and its association with grapevine leaf mottling and deformation.  Phytopathology 105:555-563. http://dx.doi.org/10.1094/PHYTO-09-14-0241-R.

Xiao, H., M. Shabanian, W. McFadden-Smith, and B. Meng.  2016.  First report of Grapevine Pinot gris virus in commercial grapes in Canada.  Plant Disease (Posted online on February 29, 2016). http://dx.doi.org/10.1094/PDIS-12-15-1405-PDN.


Responsible Party:

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


Comment Period:* CLOSED

5/22/18 – 7/06/18


*NOTE:

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


Comment Format:

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

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

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

♦  Comments may not be posted if they:

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

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

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 

 

 

Pseudocercospora theae

California Pest Rating for
Pseudocercospora theae (Cavara) Deighton 1987
Pest Rating: C

 


PEST RATING PROFILE

Initiating Event: 

On March 6, 2018, the USDA APHIS PPQ requested State Regulatory Officials to review PPQ’s consideration of deregulation of the pathogen, Pseudocercospora theae at US ports of entry.  A ‘Deregulation evaluation of established pests’ report prepared by PERAL was provided for this review.  Therefore, the risk of infestation of P. theae in California is evaluated and a permanent rating is herein proposed.

History & Status:

Background:  Pseudocercospora theae is a fungal plant pathogen in the Mycosphaerellaceae family, that causes leaf spotting known as, bird’s eye spot disease of tea (Camellia spp.). The pathogen has previously been known by its synonyms, Septoria theae and Cecoseptoria theae (Braun et al., 2012; Farr & Rossman, 2018). Holliday (1980) reported that the fungus causes a “very minor” leaf-spotting disease in tea plants.

Pseudocercospora theae has not been reported in California. In the USA, the pathogen has been reported in Florida since about 1955 and disease caused by P. theae has not been reported after 1998.  It is likely that the pathogen is present at non-detectable levels and kept under control by standard disease management practices in nurseries (PPQ, 2018).

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

Dispersal and spread: Specific information for Pseudocercospora is lacking, however, its mode of dispersal is likely to be like other species of the genus and include air-currents, rain splash/drops, infected plants and propagative material (PPQ, 2018).

Hosts: Camelia sp., C. japonica (Japanese camellia), C. sasanqua (sasanqua camellia), C. sinensis (tea tree; synonyms: Thea assamica, T. sinensis) (Farr & Rossman, 2018).  Although some species of Pseudocercospora are capable of infecting different hosts within a single family (Crous, et al., 2013), there is no evidence that this is true for P. theae (PPQ, 2018).

Symptoms:  Infected host plants exhibit circular leaf spots no greater than 2-3 mm diam., on both sides of a leaf.  The spots are at first purple red, with an indefinite yellow green border and turn white with a narrow purple red ring (Holliday, 1980) with a narrow, raised rim, followed by a dark marginal line or halo (Braun et al., 2012).

Damage Potential: Specific losses due to Pseudocercospora theae have not been reported.  Ornamental plantings of Camellia species may be affected in limited regions of California with sufficient moisture for pathogen infection and development. The climatic suitability of the pathogen encompasses Hardiness Zones 10-13 (PPQ, 2018; Margery et al., 2008).  Nursery production of Camellia species under controlled and conducive conditions for pathogen development would also be of concern in California.  However, P. theae outbreaks in Florida nurseries were successfully controlled by use of proper sanitation practices and fungicide applications (PPQ, 2018), therefore, it is likely that the same will be true for California.  If left uncontrolled, leaf spotting may lead to disease outbreaks under favorable conditions, wherein photosynthetic areas can be reduced, and in severe infections, leaf wilt and drop may be expected.

Worldwide Distribution: Asia: Nepal, Indonesia, India, China, Taiwan, Pakistan, Sri Lanka, Vietnam; Africa: Ethiopia, Malawi, Mauritius, Tanzania, Uganda; Europe: Georgia, Italy, Netherlands Antilles; North America: Florida; South America: Argentina, Brazil, Peru (Braun et al., 2012; EPPO, 2018; Farr & Rossman, 2018).

Official Control: Presently, Pseudocercospora theae is on the ‘Harmful Organism’ list for Colombia (USDA PCIT, 2018).

California Distribution: Pseudocercospora theae has not been reported from California.  The pathogen is not known to be established in California.

California Interceptions:  None reported.

The risk Pseudocercospora theae would pose to California is evaluated below.

Consequences of Introduction:

1) Climate/Host Interaction: Limited parts of California with adequate moisture, as in coastal regions of the State where Camellia species are grown, are likely to favor establishment of Pseudocercospora theae.

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

Score: 2

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

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

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

2) Known Pest Host Range: The host range is limited to Camellia [Camelia , C. japonica (Japanese camellia), C. sasanqua (sasanqua camellia), C. sinensis (tea tree)]

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.

3) Pest Dispersal Potential: Reproduction is high and dispersal conidia is through windborne conidia, and rain splash or raindrops. The pathogen is also spread through infected plant propagative material.

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: Specific losses due to Pseudocercospora theae have not been reported. Ornamental plantings of Camellia species may be affected in limited regions of California with sufficient moisture for pathogen infection and development. Nursery production of Camellia species under controlled and conducive conditions for pathogen development would also be of concern in California.  However, theae outbreaks in Florida nurseries were successfully controlled by use of proper sanitation practices and fungicide applications (PPQ, 2018), therefore, it is likely that the same will be true for California.  Uncontrolled infected plants may lose value, however, with control measures adopted, the impact is expected to be low.

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

Economic Impact: B

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.

5) Environmental Impact: Home garden plantings of Camellia species may be impacted if the pathogen was to establish under favorable environmental conditions and in the absence of adequate disease control.

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

Environment Impact:

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.

Consequences of Introduction to California for Pseudocercospora theae: 9

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 = 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.

Evaluation is ‘Not established’ in California.

Score: (0)

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

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

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

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

Final Score:

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

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

Uncertainty:

There is very limited information available on the biology of Pseudocercospora theae.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Pseudocercospora theae is C.


References:

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

Braun, U., M. Rybak, R. Rybak, and M. G. Cabrera.  2012.  Foliar diseases on tea and mate in Argentina caused by Pseudocercospora species.  Plant Pathology & Quarantine 2 (2): 103-110.  Doi 10.5943/ppq/2/2/2

Crous, P. W., U. Braun, G. C. Hunter, M. J. Wingfield, G. J. M. Verkley, H. -D. Shin, C. Nakashima and J. Z. Groenewald.  2013.  Phylogenetic lineage in Pseudocercospora.  Studies in Mycology 75: 37-114. Published online: 22 May 2012; doi:10.3114/sim0005. Hard copy: June 2013. www.studiesinmycology.org

EPPO.   2018.   Pseudocercospora theae (CERSTH).  PQR database.  Paris, France: European and Mediterranean Plant Protection Organization.  https://gd.eppo.int/

Farr, D.F., & A. Y. Rossman.  2016.  Fungal Databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA.  Retrieved August 1, 2016, from http://nt.ars-grin.gov/fungaldatabases/

Holliday, P.  1980.  Fungus diseases of tropical crops.  Cambridge University Press, New York. 607 pp.

PPQ. 2018.  DEEP report for Pseudocercospora theae (Cavara) Deighton (Mycosphaerellaceae: Capnodiales) – Bird’s eye spot. United States Department of Agriculture, Animal and Plant Health Inspection Service, Plant Protection and Quarantine (PPQ), Raleigh, NC. 4 pp.

USDA PCIT.  2017.  USDA Phytosanitary Certificate Issuance & Tracking System. Retrieved March 21, 2018. 6:36:50 pm CDT.  https://pcit.aphis.usda.gov/PExD/faces/ReportHarmOrgs.jsp.


Responsible Party:

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


Comment Period:* CLOSED

4/6/18 – 5/21/18


*NOTE:

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


Comment Format:

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

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

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♦  Comments may not be posted if they:

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Pest Rating: C

 


Posted by ls 

Colletotrichum henanense

California Pest Rating for
Colletotrichum henanense F. Liu & L. Cai 2015
Pest Rating: B

 


PEST RATING PROFILE

Initiating Event:  

On October 12, 2017, the California Dog Team a shipment of nuts of Castanea sativa (European chestnut) at a parcel distribution facility in Alameda County.  The shipment had originated in Indiana and was destined to a private citizen in Contra Costa County.  A sample of nuts were collected by Alameda County Agricultural officials, and sent to the CDFA Plant Diagnostics Branch for Diagnosis.  Suzanne Latham, CDFA plant pathologist detected the pathogen, Colletotrichum henanense in culture from the nuts. The identity of the associated pathogen was later confirmed by USDA National Identification Services at Beltsville, Maryland, and marked the first domestic detection of C. henanense in the USA.  Consequent to the California detection, all infected plant materials were destroyed. The risk of infestation of C. henanense in California is evaluated and a permanent rating is proposed.

History & Status:

Background:  Colletotrichum henanense is a distinct fungus species belonging to the vastly morphological and physiological variable C. gloeosporioides and is genetically identified from other species of the complex.  The species was originally described in 2015 from tea plants (Camelia sinensis) and Japanese thistle (Cirsium japonicum) in Xinyang, Henan Province, and Beijing, China respectively (Liu et al., 2015).  The pathogen causes anthracnose disease in its host plants.  Camellia species were affected by anthracnose disease in China where the plant species are used as in production of edible oil, processed tea and as ornamentals (Li et al., 2018; Liu et al., 2015).  The pathogen has only been reported from China until its 2017 detection in the California.

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

HostsCamellia sinensis (tea tree), C. oleifera (tea-oil tree.  Theaceae); Cirsium japonicum (Japanese thistle.  Asteraceae) (De Silva et al., 2017; Li et al., 2018; Liu et al., 2015).  The detection of Colletotrichum henanense in Castanea sativa (European chestnut) is included here (see: Initiating Event).

Symptoms: Colletotrichum henanense causes leaf spot symptoms. Leaf spots or lesions in tea-oil tree are semicircular or half-oval, brown to black with greyish-white centers.  Severely infected leaves wither and drop (Li et al., 2018).

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

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

Damage Potential:  In China, 40% of tea-oil tree yield loss has been suggested (Li et al., 2018).  A 42.5% incidence of anthracnose disease caused by C. henanense was observed in 85 of 200 young tea-oil plants grown in a nursery in Kunming, Yunnan Province, China (Li et al., 2018).  Generally, anthracnose disease can result in reduced plant quality and growth, and marketability.  Nursery productions of Camellia and chestnut are particularly at risk as nursery conditions are often conducive to infection by Colletotrichum species.  In open fields, disease development may be sporadic as it is affected by levels of pathogen inoculum and environmental conditions.

Worldwide Distribution: Asia: China; North America: USA (De Silva et al., 2017; Li et al., 2018; Liu et al., 2015).

Official Control: None reported.

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

California InterceptionsThe risk Colletotrichum henanense would pose to California is evaluated below.

Consequences of Introduction:

1) Climate/Host Interaction: Like other species of Colletotrichum henanense requires humid, wet, rainy weather for conidia to infect host plants. This environmental requirement and narrow host range may limit the ability of the pathogen to fully establish and spread under dry field conditions.

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

Score: 2

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

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

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

2) Known Pest Host Range: Presently, the host range is limited to Camellia sinensis, C. oleifera, Cirsium japonicum, and Castanea sativa.

Evaluate the host range of the pest.

Score: 1

Low (1) has a very limited host range.

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

3) Pest Dispersal Potential: Colletotrichum henanense has high reproductive potential and conidia are produced successively.  They are transmitted by wind, wind-driven rain, cultivation tools, and human contact, however, conidial germination and plant infection require long, wet periods.

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: Anthracnose-infected chestnut and camellia plants may result in lower crop value and market loss.  Nursery productions of Camellia and chestnut are particularly at risk as nursery conditions are often conducive to infection by Colletotrichum  In open fields, disease development may be sporadic as it is affected by levels of pathogen inoculum and environmental conditions. Its economic impact is evaluated as a Medium risk.

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

Score: B, C

A. The pest could lower crop yield.

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

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

D. The pest could negatively change normal cultural practices.

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

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

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

Economic Impact Score: 2

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

Medium (2) causes 2 of these impacts.

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

5) Environmental Impact: Chestnut trees cultivated and growing in open environments in California are not expected to be significantly affected by Colletotrichum henanense due to the high moisture conditions required for the development of the pathogen.  However, under humid and moist environments, the pathogen may be more of a problem particularly in ornamental plantings of Camellia in home/urban and private/public settings.

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

Environmental Impact: E

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

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

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

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

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

Environmental Impact Score: 2

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

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

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

Consequences of Introduction to California for Colletotrichum henanense10

Add up the total score and include it here.

-Low = 5-8 points

Medium = 9-12 points

-High = 13-15 points

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

 Evaluation is ‘Not Established’

 Score (0). Colletotrichum henanense is not known to be established in California and is known only from its detected in an intercepted shipment of chestnut.

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

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

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

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

Final Score:

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

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

Uncertainty:

None.

Conclusion and Rating Justification:

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


References:

 De Silva, D. D., P. K. Ades, P. W. Crous and P. W. J. Taylor.  2017.  Colletotrichum species associated with chili anthracnose in Australia.  Plant Pathology 66 (2): 254-267.

Farr, D. F., and A. Y. Rossman. Fungal Databases, U.S. National Fungus Collections, ARS, USDA. Retrieved March 16, 2018, from https://nt.ars-grin.gov/fungaldatabases/

Li, H., G. Y. Zhou, X. Y. Qi and S. Q. Jiang.  2018.  First report of Colletotrichum henanense causing anthracnose on tea-oil trees in China.  Plant Disease “First Look” paper, accepted for publication, posted 01/03/2018. https://doi.org/10.1094/PDIS-08-17-1302-PDN 

Liu, F., Weir, B.S., Damm, U., Crous, P.W., Wang, Y., Liu, B., Wang, M., Zhang, M., and Cai, L. 2015. Unravelling Colletotrichum species associated with Camellia: employing ApMat and GS loci to resolve species in the C. gloeosporioides complex. Persoonia 35: 63-86.


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 Period:* CLOSED

4/6/18 – 5/21/18


*NOTE:

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


Comment Format:

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

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

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

♦  Comments may not be posted if they:

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

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

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

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

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


Pest Rating: B

 


Posted by ls 

Citrus Leaf Blotch Virus

    California Pest Rating for
Citrus leaf blotch virus
Pest Rating: B

 


PEST RATING PROFILE

Initiating Event:

On February 26, 2018, Dr. G. Vidalakis, University of California, Director, Citrus Clonal Protection Program, informed CDFA of his detection of Citrus leaf blotch virus (CLBV) from a Bearss Lime tree at a residence in Los Angeles County.  Subsequently, an official sample, which comprised a total of 4 subsamples, was collected by the CDFA from the same Bearss Lime tree and sent to the CDFA Plant Pathology Laboratory for diagnosis. On February 27, 2018, Tongyan Tian, CDFA Plant Pathologist, detected Citrus leaf blotch virus from all four subsamples using RT-qPCR and further confirmed the identity of the pathogen by conventional RT-PCR and sequencing. A temporary Q rating was assigned to the pathogen.  The status, risk and consequences of introduction of CLBV to California are assessed and a pest permanent pest rating is proposed herein.

History & Status:

Background: In 1968, Dweet mottle virus (DMV) was initially detected and reported from Riverside, California, during re-indexing of a candidate Cleopatra mandarin variety (C. reticulata) on ‘Dweet’ tangor at the University of California Riverside Citrus Variety Improvement Program, the forerunner of the present Citrus Clonal Protection Program (CCPP).  The candidate mandarin variety had been introduced from Florida into the Program at Riverside.  The virus produced leaf chlorotic blotching symptoms that resembled, but were distinct from, symptoms produced by psorosis virus and Citrus concave gum virus.  It also produced a mild exocortis reaction in Etrog citron.  The parent tree did not show symptoms of damage caused by any known virus and the trunk appeared normal without any signs of stem pitting or bark discoloration, although small fruit, twig dieback and little new growth were apparent.  Since the virus produced symptoms only in ‘Dweet’, it was named Dweet mottle virus (Roistacher & Blue, 1968). However, Dweet mottle virus was not reported from any commercial citrus production sites nor was it observed to produce any economic losses and was detected only once after 1963 in the CCPP indexing program (Krueger et al., 2012).

Then in 1984, at the Citrus Variety Improvement Program in Spain, Navarro and other scientists reported a new graft transmissible disease that caused a bud-union incompatibility between ‘Nagami’ kumquat and ‘Troyer’ citrange rootstock. The ‘Nagami’ kumquat had been introduced from Corsica, France.  In addition to bud-union incompatibility, the presumptive virus involved caused vein clearing in certain citrus species and stem pitting in Etrog citron.  However, after shoot-tip grafting, some plants produced were compatible with Troyer, but still caused stem pitting in Etrog citron, thereby, indicating the involvement of more than one virus (Navarro et al., 1984). Galipienso et al., 2000, gave further evidence of the involvement of more than one virus by demonstrating bud union crease in certain citrus species but not others when propagated on ‘Troyer’ citrange. However, chlorotic blotching in ‘Dweet’ tangor, like those induced by DMV, and stem pitting in Etrog citron were produced by all sources of the virus.  In 2001-02, the causal agent in “Nagami’ kumquat was partially purified and characterized and given the candidate name, Citrus leaf blotch virus (CLBV) (Galipienso et al., 2001; Vives et al., 2001, 2002).  Furthermore, these researchers detected CLBV in different citrus varieties from Japan, New South Wales (Australia), Spain, and Florida, usually associated with abnormal bud union on citrange or citrumelo. Comparison of 14 CLBV isolates from Spain, Japan, USA, France and Australia showed low genetic diversity (Vives et al., 2002).  Low rates of seed transmission were demonstrated in three citrus varieties or hybrids (Guerri et al., 2004).     A few years later, Vives et al., (2005) conducted partial sequence analysis to show that Dweet mottle virus from California had over 96% sequence (high) homology with citrus leaf blotch virus from Spain and therefore, suggested that DMV may be caused by CLBV.  Both viruses induce mottling in ‘Dweet’ tangor and stem pitting in ‘Etrog’ citron and that, besides CLBV, a different pathogen causing bud-union crease and vein clearing may be present in ‘Nagami’ kumquat sources but not in DMV from California source.  This was further demonstrated by Vives et al., (2008a) by the development of full-genome cDNA clones of CLBV that caused systemic infection in agro-inoculated herbaceous and citrus host plants and induced chlorotic blotching in ‘Dweet’ tangor and stem pitting in Etrog citron, but not vein clearing in Pineapple sweet orange or bud union crease on trifoliate rootstocks.  Then in 2010, Hajeri and other researchers at the University of California, Riverside, and the USDA ARS National Clonal Germplasm Repository for Citrus and Dates (NCGRCD), Riverside, determined the complete nucleotide sequence of DMV and with phylogenetic analysis showed that DMV is an isolate of CLBV, and not a distinct species, within the genus Citrivirus.

In California, the seed transmissibility of citrus leaf blotch virus caused concern to the citrus nursery industry.  Consequently, Kreuger et al. (2012) reported that all citrus trees at CCPP and NCGRCD were tested for the presence of the virus using RT-PCR with local DMV positives and a CLBV positive from Florida as positive controls. The virus was not detected in the tested trees.  Furthermore, they failed to detect it during surveys of field trees exhibiting bud union abnormalities for the presence of specific pathogens and therefore, while the overall status of CLBV in California is presently unknown, they believe that this virus if present at all, is only at a low incidence.  This is because the close identity of CLBV and DMV has likely prevented CLBV from becoming introduced into California.  All introductions of new citrus germplasm are indexed into ‘Dweet’ tangor as well as other indicator species at CCPP and NCGRCD. Reaction of CLBV in ‘Dweet’ tangor would enable detection of this virus, even if the actual identity of the virus was not known at the time of indexing. Detection of positives or even misidentifications would have been eliminated by thermal therapy or shoot-tip grafting before release (Kreuger et al., 2005, 2012).

Citrus leaf blotch virus has been reported in China, Corsica (France), Cuba, Italy, Japan, New South Wales (Australia), New Zealand, Spain, Florida, Arkansas, Oregon, and California (USA).  In Arkansas and Oregon, the virus was found in peony plants showing stunting and gnarled irregularities, however, since the virus was found in both symptomatic and asymptomatic material, it could not be associated with the disease and its role in peony health is currently unknown.  Nonetheless, CLBV may easily move between propagation cycles via mechanical and seed transmission of clonally propagated peony plants (Gress et al., 2017).

Citrus leaf blotch virus not only causes symptomless infection in most citrus but also, is unevenly distributed within an infected plant, thereby presenting a possible challenge for its detection. In greenhouse studies, Vives et al. (2002) detected CLBV consistently in young leaves of infected ‘Nagami’ kumquat, ‘Owari’ Satsuma, Navelina and Navel oranges, however, detection in old leaves of other citrus species (Eureka lemon, Marsh grapefruit and Nules Clementine) was not consistent, particularly in Pineapple sweet orange.  Detection of the virus in field trees was even less consistent, and not detected in neighbor trees showing similar symptoms possibly due to low titer or uneven distribution of the virus in the plant.

HostsCitrus spp., including C. sinensis, C. limon, C. unshiu, C. paradisi, Poncirus trifoliata, P. trifoliata x C. sinensis (Harper et al., 2008), C. medica (Etrog citrus), C. reticulata x C. sinensis (‘Dweet’ tangor) (Roistacher & Blue, 1968), Fortunella margarita (kumquat “Nagami’) (Navarro et al., 1984), Prunus avium cv. Red-lamp (sweet cherry) (Wang et al., 2016), Actinidia sp. (kiwifruit) (Zhu et al., 2016), Paeonia lactiflora (peony) (Gress et al., 2017).  Experimental hosts include Nicotiana cavicola (Guardo et al., 2009), N. occidentalis and N. benthamiana (Vives et al., 2008b).

Symptoms: Citrus leaf blotch virus causes symptomless infection in most citrus species and cultivars (Vives et al., 2008a).  However, CLBV (and the isolate, DMV) induce chlorotic blotching or mottling in ‘Dweet’ tangor and stem pitting ‘Etrog’ citron. Although CLBV does not induce bud union crease on trifoliate rootstock (Vives et al., 2008a), it has been found to be usually associated with abnormal bud union on citrange or citrumelo rootstock. A different pathogen or interaction of CLBV with a different pathogen is likely the cause of bud union crease and vein clearing symptoms (Vives et al., 2005).

Damage Potential: Citrus leaf blotch virus causes chlorotic leaf blotching in ‘Dweet’ tangor and stem pitting in Etrog citron.  Although it does not induce bud union crease in several citrus species it is usually associated with bud union crease symptoms in citrange and citrumelo rootstocks and therefore, an interaction between CLBV and other agent(s) cannot be ruled out.  There are no reports of yield losses due to CLBV and the virus can cause symptomless infections in most citrus species and cultivars. In California, CLBV (aka DMV) is a regulated pathogen and its distribution is unknown or at best likely to be of low incidence. CLBV (aka DMV) was not reported from any commercial citrus production sites in California nor was it observed to produce any economic losses (Krueger et al., 2012).  However, in certain scion-rootstock combinations using ‘Dweet’ tangor and Etrog citron rootstocks there may be a potential for disease development due to CLBV.

TransmissionCitrus leaf blotch virus is transmitted in citrus by grafting and seed.  CLBV dispersal occurs primarily by propagation of infected buds.  Low rates of seed transmission in at least three citrus species and hybrid, ‘Troyer’ citrange (Citrus sinensis x Poncirus trifoliata), ‘Nagami’ kumquat (Fortunella margarita) and sour orange (C. aurantium), has been demonstrated (Guerri et al., 2004).  Also, CLBV has been mechanically transmitted to Nicotiana cavicola (Guardo et al., 2009), by sap inoculation to N. occidentalis and N. benthamiana (Vives et al., 2008b), and transmitted from citrus to citrus by contaminated knife blades (Roistacher et al., 1980).  The virus is not transmitted by vectors (Galipienso et al., 2000).

Worldwide Distribution: Asia: China, Japan; Europe: Italy, Spain; North America: USA, Cuba; Oceania: New South Wales (Australia), New Zealand (Cao et al., 2017; Gress et al., 2017; Guardo et al., 2007; Harper et al., 2008; Hernández-Rodríguez, 2016; Navarro et al., 1984; Roistacher & Blue, 1968; Vives et al., 2002; Wang et al., 2016).

Official Control: Citrus leaf blotch virus is on the ‘Harmful Organism’ list for Uruguay (USDA PCIT, 2018).  CLBV (aka DMV) is a regulated pathogen in California’s mandatory Citrus Nursery Stock Pest Cleanliness Program (CCR, Title 3, Division 4, Chapter 4, Subchapter 6, Section 3701).

California Distribution: The distribution in California is unknown.  If at all present, it is likely to be only at a low incidence (Kreuger et al., 2005, 2012.  See: ‘Background’).

California Interceptions: No official interceptions have been reported.

The risk Citrus leaf blotch virus would pose to California is evaluated below.

Consequences of Introduction:

1) Climate/Host Interaction: Although the distribution of Citrus leaf blotch virus in California, is presently unknown and is likely to be only at a low incidence (Kreuger et al., 2012), if not regulated, it may be possible for the pathogen to have a widespread establishment in symptomatic and non-symptomatic infected citrus varieties in commercial citrus-growing regions of the State.

Evaluate if the pest would have suitable hosts and climate to establish in California.  Score: 3

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

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

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

2) Known Pest Host Range: The natural host range is limited primarily to Citrus  Other hosts include sweet cherry and kiwifruit reported from China and peony reported from Arkansas and Oregon. Experimental hosts include, Nicotiana cavicola, N. occidentalis and N. benthamiana.

Evaluate the host range of the pest.

Score: 1

Low (1) has a very limited host range.

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

3) Pest Dispersal Potential: Citrus leaf blotch virus has high reproduction within its plant host, although unevenly distributed within infected plants. It is transmitted by grafting, seed, and mechanically. Its ability for long distance spread through infected seed render it a high rating for dispersal.

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: Citrus leaf blotch virus is a regulated pathogen under California’s mandatory Citrus Nursery Stock Pest Cleanliness Program.  Under this program any citrus stock found positive for the pathogen would be eliminated before release for commercial planting.  This pathogen causes chlorotic leaf blotching in ‘Dweet’ tangor and stem pitting in Etrog citron.  Although it does not induce bud union crease in several citrus species, it is usually associated with bud union crease symptoms in citrange and citrumelo rootstocks and therefore, an interaction between CLBV and other agent(s) cannot be ruled out.  There are no reports of yield losses due to CLBV and the virus can cause symptomless infections in most citrus species and cultivars. Researchers have stated that CLBV has not been reported from commercial citrus production sites in California nor was it observed to cause any economic losses.  If citrus stock were not regulated, it is likely that in certain scion-rootstock combinations using ‘Dweet’ tangor and Etrog citron rootstocks there may be a potential for disease development due to CLBV. In such a case, it is estimated that CLBV could lower crop yield and value and trigger the loss of markets.

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

Economic Impact: A, B, C

A. The pest could lower crop yield.

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

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

D. The pest could negatively change normal cultural practices.

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

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

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

Economic Impact Score: 3

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

– Medium (2) causes 2 of these impacts.

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

5) Environmental Impact: No environmental impact is expected, however, if not regulated, CLBV may impact home/urban plantings of citrus host plants.

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

Environmental Impact: E

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

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

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

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

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

Environmental Impact. Score: 2

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

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

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

Consequences of Introduction to California for Citrus leaf blotch virus: 12

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

-Low = 5-8 points

Medium = 9-12 points

-High = 13-15 points

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

Evaluation is (0). While the distribution of CLBV in California is currently not known, there is no evidence that it is established within the State.

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

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

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

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

Final Score:

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

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

Uncertainty:

The in-state distribution of CLBV is not currently known.  Also, the impact of infection related to crop damage and losses is not known.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Citrus leaf blotch virus is B.


References:

Cao, M. J., Y. -Q. Yu, X. Tian, F. Y. Y. and, R. H. Li and C. Y. Zhou.  2017.  First report of Citrus leaf blotch in lemon in China.  Plant Disease 101: 8.  https://doi.org/10.1094/PDIS-10-16-1500-PDN

Galipienso, L., L. Navarro, J. F. Ballester-Olmos, J. Pina, P. Moreno, and J. Guerri.  2000.  Host range and symptomatology of a graft transmissible pathogen causing bud union crease of citrus on trifoliate rootstocks. Plant Pathology 49: 308–314.

Galipienso, L., M. C. Vives, P. Moreno, R. G. Milne, L. Navarro and J. Guerri.  2001.  Partial characterization of Citrus leaf blotch virus, a new virus from Nagami kumquat.  Archives of Virology 146: 357–368.

Gress, J. C., S. Smith, and I. E. Tzanetakis.  2017.  First report of Citrus leaf blotch virus in peony in the U.S.A. Plant Disease 101: 637. https://doi.org/10.1094/PDIS-08-16-1218-PDN

Guardo, M., G Sorrentino, T. Marletta and A. Carusa.  2007.  First report of Citrus leaf blotch on kumquat in ItalyPlant Disease 91: 104.

Guardo, M., O. Potere, M. A. Castellano, V. Savino and A. Caruso.  2009.  A new herbaceous host for Citrus leaf blotch virus. Journal of Plant Pathology 91: 485-488.

Guardo, M., G. Sorrentino and A. Caruso.  2015.  Characterization and incidence of Citrus leaf blotch virus in Southern Italy.  12th International Citrus Congress – International Society of Citriculture. Acta Horticulturae 1065: 825-83.

Hajeri, S., C. Ramadugu, M. Keremane, G. Vidalakis and R. Lee.  2010.  Nucleotide sequence and genome organization of Dweet mottle virus and its relationship to members of the family Betaflexiviridae.  Arch Virol 15: 1523-1527.  DOI 10.1007/s00705-010-0758-1

Harper, S. J., K. M. Chooi and M. N. Pearson.  2008.  First report of Citrus leaf blotch virus in New Zealand.  Plant Disease 92: 1470.  https://doi.org/10.1094/PDIS-92-10-1470C

Hernàndez-Rodríguez, L., J. M. Pérez-Castro, G. García-García, P. Luis Ramos-González, V. Zamora-Rodríguez, Xenia Ferriol-Marchena, Inés Peña-Bárzaga and L. Batista-Le Riverend.  2016.  Citrus leaf blotch in Cuba: first report and partial molecular characterization.  Tropical Plant Pathology 41: 147. https://doi.org/10.1007/s40858-016-0078-4

Krueger, R. R., J. A. Bash and R. F. Lee.  2005.  Phytosanitary status of California citrus.  International Organization of Citrus Virologists Conference Proceedings (1957-20), 16 (16): 468-472.  https://escholarship.org/uc/item/3667q9qn

Krueger, R. R., J. A. Bash and R. F. Lee.  2012.  Dweet mottle virus and Citrus leaf blotch virus.  http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=7112

Navarro, L., J. A. Pina, J. F. Ballester-Olmos, P. Moreno and M. Cambra.  1984.  A new graft transmissible disease found in Nagami kumquat. In: Timmer L. W., and J. A. Dodds (eds) Proceedings of the 9th Conference of the International Organization of Citrus Virologists, IOCV, Riverside, pp 234–240.

Roistacher, C. N., and R. L. Blue.  1968.  A psorosis-like virus causing symptoms only on ‘Dweet’ tangor.  International Organization of Citrus Virologists Conference Proceedings (1957-2010), 4(4): 13-18.

Roistacher, C. N., E. M. Nauer and R. C. Wagner.  1980.  Transmissibility of cachexia, Dweet mottle, psorosis and infectious variegation viruses on knife blades and its prevention.  Proceedings of the 8th Conference of the International Organization of Citrus Virologists, IOCV, Riverside 1980: 225-229.

USDA PCIT.  2018. USDA Phytosanitary Certificate Issuance & Tracking System. Retrieved March 15, 2018. 3:25:54 pm CDT.  https://pcit.aphis.usda.gov/PExD/faces/ReportHarmOrgs.jsp.

Vives, M. C., L. Galipienso, L. Navarro, P. Moreno and J. Guerri.  2001.  The nucleotide sequence and genomic organization of Citrus leaf blotch virus: Candidate type species for a new virus genus.  Virology 287: 225-233.

Vives, M. C., L. Galipienso, L. Navarro, P. Moreno and J. Guerri.  2002.  Citrus leaf blotch virus: a new citrus virus associated with bud union crease on trifoliate rootstocks.  International Organization of Citrus Virologists Conference Proceedings (1957-2010), 15 (15): 205-212.

Vives, M. C., L. Rubio, L. Galipienso, L. Navarro, P. Moreno and J. Guerri.  2002.  Low genetic variation between isolates of Citrus leaf blotch virus from different host species and different geographical origins. Journal of General Virology 83: 2587–2591.

Vives M. C., J. A. Pina, J. Juarez, L. Navarro, P. Moreno and J. Guerri.  2005.  Dweet mottle disease is probably caused by Citrus leaf blotch virus. 16th Conference of the International Organization of Citrus Virologists Conference Proceedings (1957-2010), 15 (16): 251-256.

Vives, M. C., S. Martin, S. Ambros, A. Renovell, L. Navarro, J. A. Pina, P. Moreno, J. and J. Guerri.  2008a.  Development of a full-genome cDNA clone of Citrus leaf blotch virus and infection of citrus plants. Molecular Plant Pathology 9:787–797.

Vives, M. C., P. Moreno, L. Navarro and J. Guerri.  2008b.  Citrus leaf blotch virus.  In: Rao, G. P., A. Myrta and K. Ling (eds).  Characterization, Diagnosis and Management of Plant Viruses, vol. 2. Pp. 55-67.  Studium Press, Houston, TX, USA.

Wang, J., D. Zhu, Y. Tan, X. Zong, H. Wei and Q. Liu.  2016. First report of Citrus leaf blotch virus in sweet cherry.  Plant Disease 100:1027.

Zhu, Chen-xi, Wang, Guo-ping, Zheng, Ya-zhou, Yang, Zuo-kun, Wang, Li-ping, Xu, Wen-xing and N. Hong.  2016.  RT-PCR detection and sequence analysis of coat protein gene of Citrus leaf blotch virus infecting kiwifruit trees.  Acta Phytopathologica Sinica, 46 (1): 11.


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