Free grape virus diagnostic support this fall

Have a suspicion your vineyard may have a virus disease? Send in your infected leaf samples to MSU for a free tentative diagnosis.

September 21, 2011 - Author: Annemiek Schilder, Michigan State University Extension, Department of Plant Pathology

We will again provide free diagnostic support for suspected grape virus problems this fall thanks to a grant from the Michigan Grape and Wine Industry Council. 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 and peach rosette mosaic virus will be used.

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 or nutrient stress can also cause leaf discoloration. Viruses typically affect scattered vines throughout the vineyard, although sometimes several vines in a row are infected. The infection may also appear to be spreading.

If you suspect a virus disease and would like us to help you figure out what is going on in your vineyard, please call Jerri Gillett in the small fruit pathology lab at 517-355-7539 to set up a sampling time. You can also send fresh symptomatic leaf samples by overnight mail or drop them off at 105 CIPS Building, East Lansing, Mich. Samples can also be dropped off at an AgBioResearch 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. You can send in up to 10 samples. Make sure that the vines are tagged or numbered so that we can relate back the results to specific vines.

Please also provide the following information so we can report back to you: farm name, address and phone number, cultivar, vineyard block, symptoms observed, and date. We plan to do most of the laboratory testing in the next two to three weeks. Contact Jerri Gillett at 517-355-7539 if you have any questions.

Dr. Schilder's work is funded in part by MSU's AgBioResearch.

Tags: fruit & nuts, grapes, msu extension

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