|Statewide survey of grapevine leafroll-associated viruses and management of its vector, grape mealybug, in Virginia.|
T. J. JONES (1), N. A. Rayapati (2), M. Nita (1). (1) Virginia Tech, AHS AREC, Winchester, VA, U.S.A.; (2) Washington State University, IAREC, Prosser, WA, U.S.A.
Presence of <i>Grapevine leafroll-associated virus-2</i> (GLRaV-2), GLRaV-3, and <i>Grapevine fleck virus</i> (GfkV) was surveyed in VA during the 2009-11 seasons. These viruses can cause significant crop loss and affect wine quality by reducing sugar accumulation and compromising skin color. Petiole samples were collected from random vines from various commercial vineyards. Using a one-tube, one-step RT-PCR and PCR method, we tested over 1,300 vine samples (39 different wine grape varieties) from 136 vineyards. Testing results showed 7.3%, 24.6%, and 0.5% of sampled vines were positive for GLRaV-2, GLRaV-3, and GfkV, respectively. Moreover, 61% of sampled vineyards had at least one positive sample. The high incidence of infected vines warranted investigation into management of mealybugs, the vectors of GLRaV-3. Two field experiments were conducted at different locations: a contact insecticide (pyrethroid) treatment was tested at one experimental site, and two systemic insecticides (neonicotinoid) treatments were tested at the other. A significant increase in mealybug populations (<i>P</i><0.05) was observed at the location using the contact insecticide while a significant decrease in vector populations over time (<i>P</i><0.05) was observed at the location using the systemic materials. With the sudden awareness of viral diseases in Virginia, our review of management strategies will help developing necessary tools to prevent further spread of disease and establishment of vectors. <p><p>Keywords: Virus-Viroid, Fruits-Nuts, Grape