Red Blotch Disease Stan DeMarta VWT 35 Spring 2014

Presentation Outline Introduction/Overview Discovery Biology Symptoms Damage Distribution and Propagation Management History Conclusions

Introduction/Overview Red Blotch Disease is a newly discovered disease Not a “New” disease Presents similarly to Leafroll disease Identified as a viral disease Affects the quality of grapes more than the quantity Researchers, Vineyard Managers and Nurseries very concerned

Discovery First discovered in the UC Davis research vineyards in Oakville, CA (Napa AVA) in 2008 Visually misdiagnosed as Leafroll Disease (but assay tests were negative) In 2012 a new Virus found, highly correlates with the symptoms

Biology Grape Red Blotch associated Virus (GRBaV) – DNA Virus in the Geniniviridae Family, two strains identified – Largest family of plant viruses – Commonly vectored by insects – 2012 PCR assay test has been developed for Identification – Much is still unknown about the virus

Symptoms and Damage Appears late August through September Irregular blotches on leaf blades and basal portions of shoots Eventually the entire leaf becomes red Vineyard Distribution – Sporadic, suggesting a vector in the field Similar but not identical to Leafroll Disease Important to get vine tested to positively identify disease

Symptoms Bad News – Infects all Varietals (Red, White, wine, table) No varietals have been found to be totally resistant – Infects all Rootstock No rootstock has been found to be totally resistant – Infects Young and Old Vines

Damage More Bad News – Affects Grape Quality Can decrease brix by 3 to 6 counts Tritratable acidity is significantly increased while overall pH is only moderately reduced Delayed ripening

Damage Good News (Maybe) – No noticeable affect on yield Long term studies not yet complete – Does not kill the vine in the short term Long term studies not yet complete

Distribution and Propagation Found in all major growing areas in North America – Unconfirmed in Italy Most well known form of propagation has been from grafting in nurseries. There is evidence that there is an insect vector, but no vector has been isolated Propagation through human or mechanical means does NOT occur.

Economic Impact Too soon to quantify – How widespread will it become? – What will be the cost of Management? – What’s the cost of lower quality?

Management There is no cure! Goal: Don’t get it in the first place. Nurseries: Certified nurseries now have the tools to eliminate propagation (PCR assay Testing). – Insist on verified clean vines and rootstock. Don’t propagate unverified vines/rootstock by field grafting or transporting “Ideally” remove vines known to be infected. May be difficult economically. It is recommended that insecticides NOT be used. – Vector not known – A wide spectrum insecticide will disrupt insect ecology

Conclusions There are still many questions

Conclusions There are still many questions – What are the insect vectors?

Conclusions There are still many questions – What are the insect vectors? – What are all the paths of propagation?

Conclusions There are still many questions – What are the insect vectors? – What are all the paths of propagation? – Are there differences in varietal susceptibility/tolerance?

Conclusions There are still many questions – What are the insect vectors? – What are all the paths of propagation? – Are there differences in varietal susceptibility/tolerance? – What is the latency of the disease?

Conclusions There are still many questions – What are the insect vectors? – What are all the paths of propagation? – Are there differences in varietal susceptibility/tolerance? – What is the latency of the disease? – Can resistant or tolerant varietals be created?

Conclusions There are still many questions – What are the insect vectors? – What are all the paths of propagation? – Are there differences in varietal susceptibility/tolerance? – What is the latency of the disease? – Can resistant or tolerant varietals be created? – Can resistant rootstock be created?

Conclusions There are still many questions – What are the insect vectors? – What are all the paths of propagation? – Are there differences in varietal susceptibility/tolerance? – What is the latency of the disease? – Can resistant or tolerant varietals be created? – Can resistant rootstock be created? – And many more

History comparison Though there is still a lot unknown research has moved very quickly on GRBaV compared to past diseases. FanleafLeafrollRed Blotch First Description Graft Transmission Verified Virus Recognized Diagnostic Assay Vector transmission (?)

Questions

References 1.Marc Fuchs, Cornell University, Dept. of Plant Pathology 2. Dr. Mysore R. Sudarshana, USDA-ARS, Dept of Plant Pathology UC Davishttp://ucanr.edu/sites/viticulture-fresno/files/ pdf University of California, UC Integrated Viticulture websitehttp://iv.ucdavis.edu/Viticultural_Information/?uid=284&ds= “The Impact of Grapevine Red Blotch Virus” James A. Stamp, Ph.D. and Alan Wei, Ph.D 5.Grapevine Virus Diseases – “Grape Pet Management” Golino, Rowhani, Uyemoto