Stephen Onayemi* and Doug Walsh
*Washington State University, 24106 N Bunn Rd, Prosser, WA 99350, Prosser, WA, 99350 (dwalsh@wsu.edu)

Grape mealybugs, Pseudococcus maritimus, are the primary vector of grapevine leafroll associated viruses (GLRaVs) in Washington State winegrape vineyards and can be a late-season direct pest of fruit clusters. We demonstrated that one infected grape mealybug crawler can transmit GVLRaV-3 between 10 to 20% even with toxic doses of systemic insecticides. For the past 20 years, growers have applied imidacloprid on vineyards as cheap insurance to control Ps. maritimus. Unfortunately, growers are now reporting resistance to, and field failures with, imidacloprid chemigated for grape mealybug control. As a result, growers need to incorporate alternative IPM strategies to help hinder insecticide resistance development and slow the spread of GLRaVs. We conducted a two-year study on mating disruption for Ps. maritimus by deploying twist-tie and Cidetrak pheromone-imbibed dispensers on grapevines in an even spatial manner of 0, 10, 30, 60, and 100 emitters and 32 and 50 emitters per acre, respectively. We included sentinel traps baited with the sex pheromone of grape mealybug in two replicates (twist-tie) and three replicates (Cidetrak) of five-acre blocks per deployment rate in commercial grower vineyards in Washington from May to August of 2022. Dispensers deployed at 100 and 60 (twist-tie) and 50 (Cidetrak) emitters per acre nearly shut down the capture of male Ps. maritimus in sentinel traps. This research is heartening and demonstrates that mating disruption of grape mealybug may have potential applications in winegrape vineyards.

Funding Support: Washington State Wine Commission