Vineyard proximity to riparian habitat influences Western grape leafhopper (Erythroneura elegantula Osborn) populations

The purpose of this study was to evaluate the impact of vineyard proximity to riparian habitat on the biological control and population densities of the Western grape leafhopper, Erythroneura elegantula Osborn (Hemiptera: Cicadellidae). Natural enemy and pest populations were monitored over a two-year period at multiple vineyard sites adjacent to riparian habitat in northern California. At each site, natural enemy and pest population data were collected along a transect that extended from the riparian habitat into the vineyard. Additionally, a subset of the original research sites were further evaluated for crop vigor, pest density and parasitism rates between the vineyard edge and interior. Results from this study indicate that lower E. elegantula egg deposition and nymph abundance at the vineyard edge were primarily due to reduced crop vigor at the sampled sites and that the most likely cause for these changes were differences in microclimate and soil fertility that were found to be associated with proximity to the riparian habitat.