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