Grape virus diagnostic support during the 2012 growing season
Free diagnosis of grapevine viruses proved by Michigan State University.
We will again provide free diagnostic support for suspected grape virus problems this season. Even though symptoms can lead us to a tentative diagnosis, virus diseases can only be positively confirmed using laboratory tests, such as ELISA (enzyme-linked immunosorbent assay). This type of test uses sap from ground-up grape leaves in an enzymatic reaction with antibodies from animals. At the end of the two-day process, a yellow color indicates that the virus is present in the plant tissue. No color reaction indicates a negative outcome. Test kits for grapevine leafroll viruses (1 through 9), Grapevine virus A, Grapevine virus B, tobacco ringspot virus, tomato ringspot virus, grapevine fanleaf virus, grapevine fleck virus and peach rosette mosaic virus will be used. These tests can also be done on weeds (e.g., dandelion) in prospective grape plantings to determine if dagger nematode-transmitted viruses that have a wide host range, such as tobacco ringspot virus and tomato ringspot virus, are present in the field prior to planting.
Grapevine viruses cause various types of symptoms, including dead and dying vines, weak vines, few clusters with small berries, uneven berry size, uneven or late ripening, small or misshapen leaves, leaf curling, leaf reddening or yellowing, ring-like patterns or mottling. Not all leaf reddening is caused by viruses – sometimes crown gall, wounding, drought stress or nutrient deficiencies can also cause leaf discoloration. Viruses typically affect scattered vines throughout the vineyard, although sometimes several vines in a row may be infected. Soilborne (nematode-transmitted) viruses are often associated with spreading, roughly circular patches of declining and dying vines. The infection may also appear to be spreading and getting worse from year to year. Symptoms may be more pronounced in cool growing seasons.
If you suspect a virus disease and would like us to help you figure out what is going on in your vineyard, please let us know. We plan to run three batches of tests: around mid-June, mid-August and mid- to late September. We will send out a reminder one to two weeks before we plan to run the tests so you can arrange for sampling. Leaf roll viruses are best sampled later in the season, when symptoms are more pronounced and virus concentration in the leaves is higher. You can also send fresh symptomatic leaf samples by overnight mail or drop them off at:
for Integrative Plant Systems – Lab Building
578 Wilson Rd. Room 105
East Lansing, MI 48824
Samples can also be dropped off at an MSU research station, but do let us know so we can arrange for transport to the MSU campus.
Select the most symptomatic leaves and keep samples from different vines separate. Samples should be refrigerated as soon as possible and kept cool until delivered to the lab. The samples should be as fresh as possible. Make sure that the vines are tagged or numbered so that we can relate the results to specific vines.
Please also provide the following information so we can report back to you: farm (+ address and phone number), cultivar, vineyard block, symptoms observed and date. If you have any questions, please contact Jerri Gillett in the Small Fruit Pathology Lab (517-355-7539).
Dr. Schilder’s work is funded in part by MSU‘s AgBioResearch.