One Finger Lakes grower sampled his own 'Cabernet Franc' vines and concluded that the fruit from these vines would never ripen properly, even in exceptional years. The grower replaced more than 1,000 infected vines. Nurseries in New York and elsewhere are motivated to change their practices in collecting and propagating vines to eliminate nursery-based transmission of infected vines. The extension publication has been widely reproduced in states throughout the Northeast and in national trade magazines.
impact statement issue
At one 'Lemberger' (red wine grape) vineyard, Marc Fuchs noted typical leaf roll virus symptoms on most vines, tested them for virus, and found a high incidence of three leaf roll strains. The follow-up survey over three years showed that 68% of a random sample of Finger Lakes vineyards had some level of leaf roll virus infections. It was unclear whether or not the virus could spread through insect vectors.
impact statement response
Our survey raised awareness of the fact that leaf roll virus is common in New York, probably mostly introduced through nursery stock. Follow-up surveys over three years confirmed limited within-vineyard spread, and grapevine mealybug was identified as a New York vector capable of spreading infection.
The fruit maturity sampling of adjacent infected and uninfected vines showed significant decreases in sugar level at harvest (2 to 5% lower brix). Extension publications, reproduced in Ohio, Pennsylvania, Virginia, and elsewhere, outlined the problem and management strategies to deal with it.
impact statement summary
Our survey of 95 Finger Lakes vineyards found 68% infected with low to high levels of grapevine leafroll viruses. One-third had high levels of infection (greater than 20% of vines). We suspect that most infections started with transmission through nursery stock. Follow-up studies found that grapevine mealybugs carry the viruses and are capable of causing spread within vineyards. A further study of fruit composition at harvest showed fruit quality in infected vines diminished, with lower brix (sugar levels), higher pH, and less crop. In short, vines impacted with leafroll virus produced less fruit at lower maturity levels. Our survey and outreach to the industry has prompted growers to understand that leafroll virus can spread, that infected vines produce less fruit of inferior quality, and that they should be replaced. Efforts are underway through the National Clean Plant Network to produce virus-free, certified vines for establishing clean vineyard blocks.
