Statewide wine grape virus survey underway
This survey will help determine the prevalence of grape viruses in Michigan that cause production problems. Samples included in survey can be submitted until Oct. 14, 2016.
Funded by the Michigan Grape and Wine Industry Council, a statewide survey in wine grapes is currently underway in Michigan to determine the prevalence of grape viruses that can cause vine decline, low yields, poor fruit quality or other production problems. Leaf samples are taken in 100 randomly selected wine grape vineyards in the main grape-growing regions in Michigan. Samples will be tested for 22 different viruses and 2 types of specialized bacteria (Xylella and Phytoplasma) known to infect grapes. While we already know that a number of these viruses are present, others have not been confirmed yet in Michigan. The goal of the survey is to more accurately determine which viruses are present and how common they are in Michigan vineyards.
Wine grapes were chosen because they tend to have more virus problems than juice grapes. Both Vinifera and hybrid grapes are included in the survey. Once viruses have been identified, a course of action needs to be decided on: leave the vines in place, remove vines, and/or plant new vines using virus-tested plant material. Virus vectors such as mealybugs and nematodes also have to be taken into account to determine the risk of spread or reinfection. In general, using virus-tested planting stock is the best way to prevent virus infection.
For virus-testing, the sample has to be as fresh as possible. Select symptomatic vines (up to five vines per vineyard) and collect five leaves of about intermediate age ̶ not too young and not too old ̶ per vine. Snap the leaves off at the cane, thus including the petiole, stick them in a plastic Ziploc bag and place them in a cooler. If leaves are wet from rain or dew, pat them dry with paper towels and wrap them in dry paper towels. Do not leave samples out in the sun for any length of time as the bags can quickly heat up, inactivating viruses.
When taking samples, make sure not to touch the cut end of the petiole, as virus particles can be present in plant sap and can cause contamination among samples. Keep the leaves refrigerated and send them by overnight mail or deliver them to our lab at: Center for Integrated Plant Systems, 578 Wilson Road Room 15, East Lansing, MI 48824. Provide the following information: cultivar/rootstock, vine age, vineyard/vine number and grower name and contact information to send the report to. Please make sure to inform us that samples are coming so we’ll be prepared to receive them.