Susceptibility of grape berry moth, Paralobesia viteana (Clemens) (Lepidoptera: Tortricidae) to insecticides in Michigan vineyards

Grape berry moth is a major pest of vineyards across eastern North America. Increasing infestations in Michigan commercial vineyards under active pest management have raised concerns about insecticide resistance in this species. We tested the susceptibility of male moths of this pest from 5 vineyards in southwestern Michigan over 2 years using a range of concentrations, followed by probit analysis of the resulting mortality data. In 2021 and 2022, topical applications of phosmet and zeta-cypermethrin were applied to moths collected from each vineyard, and the LC50, LC90 and LC99 values were calculated for each population. The LC50 values were similar among sites, whereas the LC99 values for phosmet were highly variable across years, with sensitivity 2.78 times higher in 2022 than 2021 at Farm 2 and 61.66-fold higher in 2021 at Farm 3. Sensitivity to zeta-cypermethrin was generally similar between years at the LC50 level, but it was variable at the LC99, with two sites showing lower sensitivity in 2022 compared to 2021 and three farms with an increased sensitivity in 2022. The response to carbaryl was similar for Farm 3 across both years. However, in 2022 the LC50, LC90 and LC99 values in Farm 3 were 2.34, 6.33 and 14.29-fold, respectively, higher compared to those in Farm 5. In conclusion, our results show that sensitivity to insecticides in grape berry moth populations in southwest Michigan vineyards is highly variable between different farms and across years. These results highlight the need for continued monitoring of sensitivity to insecticides in this species, and development and implementation of alternative control strategies in vineyards to maintain pest susceptibility to insecticides.

Automated summary

Sensitivity to insecticides in grape berry moth populations in southwest Michigan vineyards is highly variable between different farms and across years. Continued monitoring of sensitivity and development of alternative control strategies are needed to maintain pest susceptibility to insecticides in vineyards.