DISPERSAL AND MOVEMENT OF THE GLASSY-WINGED SHARPSHOOTER AND ASSOCIATED NATURAL ENEMIES IN A CONTINUOUS, DEFICIT-IRRIGATED AGRICULTURAL LANDSCAPE

Outlined experiments in this study have only recently begun and are designed to advance our ability to define the operative host-plant factors utilized by adult glassy-winged sharpshooter (GWSS) and associated natural enemies as long-range cues to locate feeding and oviposition hosts in a complex agricultural landscape. Specifically, experiments are underway to determine how continuous deficit irrigation regimes in Valencia oranges influence the population dynamics of GWSS and other associated natural enemies. Populations of GWSS were monitored in a citrus orchard maintained under continuous irrigation schedules receiving 60%, 80%, and 100 % of evapo-transpiration (ETc) rates. Throughout the season, citrus trees irrigated at 60 % ETc had warmer leaves and higher water potential than the trees irrigated with 80 % and 100 % ETc. Mean numbers of adults collected on beat samples, caught on sticky traps, and observed during the visual inspection, and egg masses within foliage were higher in the 80 % and 100 % ETc treatments than the 60 % ETc treatment. Preliminary caged experiments using grape and oleander conducted in Riverside, California, illustrated GWSS population shifts that occurred between plants. Individual plants maintained under a well-watered treatment (ETc=100%) exhibited higher insect counts compared with a continuous deficit-irrigated treatment (ETc=50%). Identifying how the dispersing lifestages of GWSS locate and exploit specific host species will begin to provide the necessary information required to develop strategies for control of this highly mobile insect and further to limit the spread of Xf movement into susceptible crops