INTERSPECIFIC COMPETITION BETWEEN GONATOCERUS ASHMEADI, G. TRIGUTTATUS, AND G. FASCIATUS FOR GLASSY-WINGED SHARPSHOOTER EGG MASSES

• Author(s): Hoddle, Mark; Irvin, Nic;
• Abstract: Interspecific competition between G. ashmeadi, G. triguttatus and G. fasciatus for GWSS egg masses was investigated in the laboratory using three experimental designs. Overall parasitism by G. ashmeadi was consistently higher (up to 76.0%) compared with G. triguttatus and G. fasciatus, for all three experimental designs. Exposing females to individual egg ages (1, 3 or 5 days) showed that G. ashmeadi parasitized a significantly higher (48.1%) proportion of GWSS eggs compared with G. triguttatus, whereas when females were exposed to all egg ages simultaneously, parasitism by G. ashmeadi and G. triguttatus was equivalent. Results from visual observations showed that G. triguttatus allocated a significantly higher (up to 36.4% and 22.9%, respectively) proportion of time to resting/grooming, compared with G. ashmeadi and G. fasciatus. Gonatocerus fasciatus spent a greater (19.6% and 9.6%, respectively) proportion of time off leaves with GWSS egg masses compared with G. ashmeadi and G. triguttatus. Gonatocerus triguttatus parasitized a significantly higher proportion (25%) of GWSS eggs compared with G. fasciatus, whereas time allocated to oviposition by each species was equivalent. Gonatocerus ashmeadi and G. triguttatus demonstrated aggressive behavior towards congeneric competitors for GWSS egg masses, whereas no aggressive behaviors were observed for G. fasciatus. The implications of these results for interspecific competition and biological control of GWSS by these three mymarid parasitoids are discussed.
• Publication Date: Aug 2003
• Journal: 2003 Pierce's Disease Research Symposium