Greeneria uvicola | Pest Rating Proposals and Final Ratings

California Pest Rating Proposal for

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

Pest Rating: B

PEST RATING PROFILE

Initiating Event:

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

History & Status:

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

Hosts: Grapevine (Vitis spp.).

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

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

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

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

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

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

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

California Distribution: Greeneria uvicola is not reported from California.

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

The risk Greeneria uvicola would pose to California is evaluated below.

Consequences of Introduction:

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

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

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

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

Risk is Low (1) – The requirements for a suitable climate of long periods of warm rains in spring, followed by warm, humid summers would not likely favor or greatly limit the establishment of Greenaria uvicola in California where grape is usually cultivated under warm and dry conditions.

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

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

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

Risk is Low (1) – Grape (Vitis spp.) is the only host. Although the host range is very limited, in California grape is a major crop that is cultivated over significant acreage.

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

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

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

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

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

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

A. The pest could lower crop yield.

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

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

D. The pest could negatively change normal cultural practices.

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

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

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

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

– Medium (2) causes 2 of these impacts.

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

Risk is High (3) – Bitter rot diseased fruit is rotted and has a bitter taste that results in finished wine with an unpleasant bitter or burnt flavor. Therefore, Greeneria uvicola-infected fruit could lower crop yield of healthy fruit bunches, lower crop value, and trigger loss of markets of table and wine grapes.

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

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

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

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

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

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

Score the pest for Environmental Impact. Score:

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

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

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

Risk is Medium (2) – Home gardens cultivated with table and/or wine grapes could be significantly impacted if infected with the bitter rot pathogen.

Consequences of Introduction to California for Greeneria uvicola:

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

-Low = 5-8 points

–Medium = 9-12 points

-High = 13-15 points

Total points obtained on evaluation of consequences of introduction of Greeneria uvicola to California = 9

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

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

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

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

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

Evaluation is not established in California (0).

Final Score:

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

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

Uncertainty:

None.

Conclusion and Rating Justification:

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

References:

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

http://www.eppo.int/DATABASES/pqr/pqr.htm .

Farr, D. F., and A. Y. Rossman. 2015. Fungal Databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved January 12, 2016, from http://nt.ars-grin.gov/fungaldatabases/

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

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

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

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

Responsible Party:

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

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