Comparative dispersal of Homalodisca coagulata and Homalodisca liturata (Homoptera : Cicadellidae)
California's viticulture and ornamental industries have suffered significant losses since the introduction of Homalodisca coagulata (Say), an important vector of the Pierce's disease bacterium. A better understanding of the factors that influence the dispersal of H. coagulata, as well as other native sharpshooters could enhance our ability to institute areawide management programs. Studies were conducted to establish the validity of an immunoglobulin G (IgG) protein marker for sharpshooter dispersal studies, to compare the dispersal of H. coagulata with that of a native sharpshooter Homalodisca liturata Ball, and to develop a better understanding of the factors that influence their dispersal. Field trials showed that the marker remained detectable for at least 19 d and did not affect sharpshooter survival. Four concentrations (0.04, 0.2, 1, and 5 mg/ml) and two different IgG markers (chicken and rabbit) were effective for marking sharpshooters. In mass-mark-recapture studies, approximate to95% of the marked insects flew during the releases and the timing of flight initiation was similar for H. coagulata and H. liturata. Mean wind speeds >3 m s(-1) were associated with a decline in flight initiation for both species. Most sharpshooters were trapped at heights below 4.2 m, and based on sex ratio comparisons, traps were equally attractive to males and females. Regression analyses of recapture data and a diffusion model were used to assess and compare sharpshooter dispersal. The majority (95%) of H. coagulata and H. liturata were recaptured within 90 and 155 m of the release site, respectively.