Adult Age Structure and Trends in Xylella fastidiosa Incidence in Homalodisca vitripennis (Hemiptera: Cicadellidae) from Texas Grape Vineyards
The glassy-winged sharpshooter, Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae), is the primary insect vector of the xylem-limited plant pathogen Xylella fastidiosa fastidiosa Wells (Xanthomonadales: Xanthomonadaceae), the bacterium that causes Pierce's disease of grape, Vitus sp. Because it is mobile and polyphagous, the glassy-winged sharpshooter is key to Pierce's disease outbreaks in California, Florida, and Texas. Adult age structure and X. fastidiosa foregut infectivity rates of glassy-winged sharpshooter from nine Texas vineyards in summer 2007 were assessed from archived samples. The ages of individuals were determined by measuring the red pigmentation of forewing intersections. Presence or absence of X. fastidiosa was determined in the foregut of pathogen-positive insects by quantitative PCR. Larger amounts of the associated pathogen in insects from two vineyards sampled in 2005 and 2006 were observed. No significant differences in average insect age among vineyards or collection dates were found in those years. However, significant differences in average pathogen load among multiple vineyards and collection dates were observed.