Date: December 15, 2014
Project Title: Sampling, Identification & Control of Leafhopper Pests in Washington Vineyards
Principal Investigator(s): Douglas Walsh, PhD, Professor of Entomology
Organization: WSU Prosser
Email: dwalsh@wsu.edu; Phone: 509-786-9287
Principal Investigator(s): Laura Lavine, PhD, Professor of Entomology
Organization: WSU Pullman
Email: lavine@wsu.edu; Phone: 309-335-7907
Collaborator(s):
Holly Ferguson, PhD, Extension IPM Coordinator Specialist, WSU Prosser
Mark Lavine, PhD, Post Doctoral Researcher, Entomology WSU Pullman
Project Budget Number: 13Z-3343-7789, OGRD 124347
I. Project Summary:
Two species of leafhoppers, the Western Grape and the Virginia Creeper Leafhoppers (WGLH and VCLH), are direct pests of grapes due to their feeding damage, nuisance pests for vineyard workers, and suspected vectors for grapevine red blotch, a viral disease recently introduced into Washington State, which causes a dramatic drop in Brix (sugar content) of ripened fruit on infected vines. Disparity may exist between leafhopper species in their ability to vector the disease. In the early 2000s, Walsh conducted sampling studies that determined that most grape growers treated their vineyards for leafhoppers when population abundance exceeded 15 per leaf. No distinctions among leafhopper species were made in these studies. Grape entomologists have paid little attention to leafhopper research for the past ten years, focusing instead on mealybugs. Given the emergence of grapevine red blotch, it is important to reinitiate studies on leafhopper abundance in grapes and follow grower treatment decisions based on leafhopper abundance. In 2013 we initiated leafhopper surveys in Washington State vineyards. We continued surveys in 2014 to further refine leafhopper sampling, identification, and control strategies.
Objectives of Research:
- Investigate sampling methods for quantifying leafhopper abundance in grape vineyards.
- Develop a DNA barcode method to differentiate WGLH and VGLH from one another.
- Conduct insecticide efficacy studies to determine if there are differences between WGLH and VCLH in response to commercially available and prevalent insecticides.
At each vineyard site, field sampling consisted of looking at 100 leaves for presence/absence of leafhoppers, scanning 20 leaves with a hand lens for field counts of leafhoppers, and bringing back ten of those 20 leaves to the lab for counting and identification to species. Leafhopper nymphs identified to species were placed in vials with 95% alcohol and sent to Pullman for DNA barcoding analysis. Since insecticides commonly used against leafhoppers (mostly imidacloprid products) are still very effective, insecticide efficacy studies were deemed not necessary. Growers were kept informed if leafhopper infestations approached economic levels. Results will be reported at industry and entomology meetings. Ultimately, we will provide updated knowledge of leafhopper abundance and species to improve leafhopper management strategies for Washington State grape growers.
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