Pilot studies on mating disruption for grape mealybug, Pseudococcus maritimus (Ehrhorn) in Washington State

Grape mealybugs, Pseudococcus maritimus, are the primary vector of grapevine leafroll associated viruses (GLRaVs) in Washington State wine grape vineyards and can be a late-season direct pest of fruit clusters. We have demonstrated that one infected grape mealybug crawler can transmit GVLRaV-3 between 10 to 20% even in the presence of 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 chemigation for grape mealybug control. As a result, growers need to incorporate alternative IPM strategies to help hinder insecticide resistance development and slow down the spread of GLRaVs. We have conducted a pilot study on a mating disruption for Ps. maritimus by deploying twist-tie pheromone-imbibed dispensers on grapevines in an even spatial manner (of 0, 10, 30, 60, and 100 emitters per acre), including sentinel traps baited with the sex pheromone of grape mealybug in two replicates of 5-acre blocks per deployment rate in a commercial grower vineyard near Paterson, WA from May to August of 2021. Dispensers deployed at 100 and 60 emitters per acre nearly achieved a shut-down of 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 wine grape vineyards.