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.

For virus sampling, collect five leaves per vine with petioles attached. Do not touch the petiole ends.

For virus sampling, collect five leaves per vine with petioles attached. Do not touch the petiole ends.

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.

If you have been wondering about leaf discoloration, stunting or other symptoms on your grapevines and would like to have some samples included in the survey, please contact me at .(JavaScript must be enabled to view this email address) or 517-355-0483. This is the last chance for free virus testing of grapevines; typically, testing by a commercial lab runs about $300-350 per sample. Just as a reminder, not all leaf reddening is caused by viruses, as nutrient deficiencies, low soil pH, and crown gall can cause symptoms similar to virus infection. For nutrient analysis, send leaf petioles to the Michigan State University Soil and Plant Nutrient Laboratory or A&L Great Lakes Laboratories in Indiana. Sample instructions can be found on the respective websites.

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.

Leaf in plastic bag

Place leaves in plastic bag, seal and place in cooler or refrigerator immediately.

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.

If you have any questions, please contact me at .(JavaScript must be enabled to view this email address) or 517-355-0483. Samples can be submitted until Oct. 14, 2016. 

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