Statewide Survey to Determine Diversity and Impact of Grapevine Viruses, Phytoplasmas and Insect Vectors on the Michigan Wine Grape Industry

Research Date
Annemiek Schilder, Rufus Isaacs, Brad Baughman, Duke Elsner, Naidu Rayapati, Assunta Bertaccini
Best Practices, Crop Quality, Disease Management, Pest Management
Crop Categories
Beverage Categories

During late summer of 2016, 438 composite grape leaf samples were taken from wine grape vineyards in mid, southwest and northwest Michigan. Over 100 different vineyards were sampled. Testing was conducted on each sample using real-time polymerase chain reaction (RT-PCR) at the Foundation Plant Services facility on the UC Davis campus. Each sample was tested for 28 different viral or phytoplasma pathogens. In all, only 45 of the 438 samples (10%) were negative for all of the tested pathogens. A large number of samples (85%) tested positive for GRSPaV. Other commonly found pathogens were GLRaV 28% (any strain), GFkV 17%, GVA 11% and TRSV 12%. We are still in the process of analyzing the data and looking at associations between virus incidence and region and cultivar. It is initially noteworthy that a high percentage of the samples (85%) were positive for Grapevine stem pitting virus and that only 10% of the samples were negative for all pathogens tested. The results of this survey suggest that there is a significant number of Michigan grapevines that are infected with virus. We will continue to analyze the data to determine if all four samples from a field were uniformly infected with the same viruses. Additionally, we will determine if there are certain virus combinations that occur regularly in the same vines. It has been shown in other crops that synergism of symptoms can occur when multiple viruses infect the same plant. If certain virus combinations occur, it would be interesting to return to those fields and make a detailed analysis of symptoms and fruit quality and yield loss. We know the grape variety for most of the survey samples, therefore we will also look to see if certain varieties of grape are more prone to specific viruses.

View: Statewide Survey Determine Diversity Impact of Grapevine viruses phytoplasmas Insect Vectors (PDF)

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