The effectiveness of organic and conventional pesticides on grape leafhoppers in Washington state vineyards

Erythroneura elegantula and Erythroneura ziczac are the two grape leafhopper pests in Washington state vineyards. Organic producers do not have an effective way of controlling these pests which can cause substantial economic loss. Pesticide resistance can build in insects which is a concern for conventional growers. E. elegantula had developed a resistance to DDT. Within a vineyard this study tested the effectiveness of bio-pesticides and conventional pesticide some of which have not been used to control leafhoppers previously. Bioassays were also performed to obtain the LC₅₀ and LC₉₀ of the non-systemic pesticides. Of the bio-pesticides tested, Pyganic was the only one found effective in both the field and laboratory components of this study. All the conventional pesticides tested significantly reduced leafhoppers compared to the control. Sivanto was found to be the most effective of the new conventional pesticides tested and the only one to achieve 100% mortality in the field. This study showed that organic vineyards can use Pyganic to control outbreaks of grape leafhoppers. It also showed that there are several effective conventional pesticides that can be added to growers Integrated Pest Management programs to help prevent pesticide resistance in grape leafhoppers.