Dispersal of Homalodisca vitripennis (Homoptera : Cicacellidae) from a point release site in citrus
The glassy-winged sharpshooter, Homalodisca vitripennis (Germar), is an important vector of Xylella fastidiosa Wells et al., a bacterium that has caused substantial losses in the viticulture and ornamental industries in California. Area-wide management programs have been implemented to reduce vector populations and limit the spread of this disease. However, there is still a lack of information on the factors that influence this insect's movement within and between host crops. In this study, we used mark-release-recapture (MRR) to examine the dispersal of H. vitripennis in a mature orange grove, Citrus sinensis Osbeck. Insects were doubly marked with chicken or rabbit immunoglobulin G (IgG) proteins and fluorescent dusts to enable monitoring over several weeks. Our objectives were to examine the reliability of IgG protein markers relative to fluorescent dusts, determine how sharpshooter movement differed in this landscape relative to a previous study, and develop a better understanding of the biotic and abiotic factors that could influence sharpshooter dispersal. Linear regressions of recapture data with a diffusion model provided significant fits to the data in five of six releases. Recapture data were fitted to a diffusion model, and based on parameters generated with the model, estimated dispersal distances for H. vitripennis at 72 h showed 50 and 99% remained within annuli of 31 and 150 m from the release site, respectively. Flight activity was greatest between 1000 and 1400 hours, and no flights occurred between 2200 and 0600 hours. Only temperature explained a significant amount of the variability in recapture of H. vitripennis, with sharpshooters rarely trapped below 18 degrees C.