Effect of vineyard proximity to riparian habitat on biological control of the western grape leafhopper (Erythroneura elegantula) in northern California wine grape vineyards

The area, arrangement and species composition of natural habitats surrounding an agroecosystem can potentially influence a number of ecosystem services beneficial to crop production, including biological control of pests. Previous research conducted in wine grapes has indicated that proximity to riparian habitat in particular can influence vineyard pest densities. This is because riparian areas are thought to contain certain plant species that serve as overwintering habitat for key natural enemies of vineyard pests. As such, vineyard proximity to riparian habitat may influence the abundance and impact of natural enemies on grape pests. In this study, multiple vineyards adjacent to riparian habitats were monitored over 2 years. Samples were taken at increasing distances away from the riparian habitats (up to 200 m). Data was collected on pest and natural enemy densities as well as pest parasitism rates. Results are accompanied by a parallel study to determine natural enemy overwintering habitat preferences.