Grape Virus Diagnostic Support

Michigan State University (MSU) will again provide free diagnostic support for suspected grape virus problems this season, according to MSU plant pathologist Annemiek Schilder. Even though symptoms can lead 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.

To read Schilder’s complete report, and to learn how to send samples, click here.