Submitted to: CDFA Pierce's Disease Control Program Research Symposium
Publication Type: Proceedings
Publication Acceptance Date: 12/15/2002
Publication Date: 12/15/2002
Citation: BLACKMER, J.L., SIMMONS, G.S. SAMPLING, SEASONAL ABUNDANCE, AND COMPARATIVE DISPERSAL OF GLASSY-WINGED SHARPSHOOTERS IN CITRUS AND GRAPES: DISPERSAL PROGRESS REPORT. CDFA PIERCE'S DISEASE CONTROL PROGRAM RESEARCH SYMPOSIUM. 2002. pp. 126-128 Interpretive Summary:
Technical Abstract: Mark-release-recapture (MRR) studies with GWSS and STSS were conducted in 2001 in Moreno Valley in an abandoned alfalfa field, and in 2002, additional releases of GWSS were carried out in a Valencia orchard in Fillmore, CA. Environmental parameters were monitored at each site. Physiological parameters, such as egg load, weight and sex ratio were also measured. Recapture data generated from these studies were fit to a diffusion model and model results were used to estimate dispersal distances for each species in each habitat. Sharpshooters were recaptured on cylindrical yellow sticky traps that were placed at various heights (from ground up to 7 m). In a separate study, movement of GWSS was measured relative to time of day, environmental parameters, and xylem flux. Sticky traps were changed and xylem sap was collected at four-hour intervals from 0600 to 2200 h. Linear regressions of recapture data with the diffusion model provided significant fits to the data with high coefficients of determination for all of the GWSS and 3 of the 4 STSS releases in 2001, and for 5 of the 6 releases in 2002. In 2001, calculations of dispersal distances using the diffusion model showed that 50 and 95% of the GWSS moved 30 and 90 m in 5-6 hr, respectively, while 50 and 95% of the STSS moved 47 and 155 m, respectively. In 2002, calculations of dispersal distances for these releases showed that 50 and 95% of the GWSS moved 30 and 99 m in 72 hr, respectively. In separate stepwise regression analyses, trap distance from the release site was the best predictor of trap catch (R2 = 0.38, P<0.0001 for GWSS and R2 = 0.31, P<0.0001 for STSS in 2001; R2 = 0.23, P<0.0001 in 2002). In 2001, the addition of trap height, release date, height*distance interaction accounted for an additional 20-31% of the variability in trap catch. In 2002, the addition of trap height, release date and cardinal position only accounted for an additional 10% of the variability in trap catch. Recapture rates were considerably lower in the citrus orchard as compared to the open field setting (1.6% in 72 hr vs. 12% in 6 hr). For all releases, sharpshooters were recaptured most often below 3m. We found that sharpshooters were most active, in terms of flight activity, between 1000 and 1400 h in the citrus setting, and of the environmental parameters measured only temperature explained a significant amount of the variability in trap catch in 2002 (R2 = 0.58, P< 0.0001). Sharpshooters were rarely trapped when temperatures fell below 18 C.