Impacts of Grapevine Leafroll Virus on Chardonnay Vines and the Role of Potential Vectors

Research Date
2014
Authors
Annemiek Schilder, Rufus Isaacs, Paolo Sabbatini, Naidu Rayapati, Forrest Nutter, Mike Merchant
Priorities
Crop Quality, Disease Management, Pest Management
Crop Categories
Grapes
Beverage Categories
Wine

Grapevine leafroll disease was widespread in the 'Chardonnay' study vineyard, with 85% of live vines showing symptoms ranging from mild to very severe. In ELISA tests, 99% of vine samples tested positive for the virus (GLRaV-3) regardless of symptom severity. Thus estimating infection based on symptoms may underestimate the actual infection incidence. In addition, 19% of the vines had Tobacco ringspot virus (TRSV) symptoms, but fewer tested positive for the virus. Both viruses were well distributed throughout the vineyard, but there appeared to be fewer vines with grapevine leafroll symptoms where there was high TRSV incidence, although about 10% of the vines showed symptoms of both viruses. Statistical analysis of spatial patterns of virus symptoms and winter injury is ongoing. Fruit yields were very low and variable throughout the field due to winter injury. Yields declined with increasing symptom severity, with moderate, severe, very severe, and very severe + TRSV categories having 2, 70%, 85%, and 91% lower yields than apparently healthy vines, respectively. Mealybugs were found throughout this and surrounding vineyards and were identified as the grape mealybug, Pseudococcus maritimus. In another leafroll virus-infected vineyard in Jackson Co., numerous boxelder bugs were found but it is unknown if they can vector plant virus vectors. Samples of both types of insects are currently being tested for the presence of leafroll viruses by PCR in Prosser, WA. This study shows that leafroll viruses can be damaging to grapevines, especially in combination with TRSV, and that mealybugs are the likely vectors of leafroll viruses in Michigan vineyards. The results also highlight the importance of clean plant material for vineyard establishment. Guidelines for prevention and management of grapevine virus diseases and their vectors will be formulated upon conclusion of the project.

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