INVESTIGATING THE BEHAVIOR AND BIOLOGY OF EXOTIC MYMARID PARASITOIDS RELEASED FOR GLASSY-WINGED SHARPSHOOTER CONTROL, AND EVALUATING TECHNIQUES FOR ENHANCEMENT IN THE FIELD

• Author(s): Hoddle, Mark; Luck, Robert; Triapitsyn, Serguei;
• Abstract: Glassy-winged sharpshooter (GWSS), Homalodisca coagulata (Say) (Hemiptera: Cicadellidae), is an exotic insect pest in California that vectors a phytopathogenic xylem-dwelling bacterium, Xylella fastidiosa. This bacterium causes serious scorch-like maladies in a variety of economically important plants including grapes {Pierces disease (PD), almonds (almond leaf scorch), and oleanders (oleander leaf scorch)}. Pesticide use has increased dramatically in citrus orchards (major crop reservoir of GWSS) adjacent to vine yards as sprays are applied to suppress populations of migratory GWSS into grapes in spring. Increased use of broad-spectrum insecticides to control GWSS has severely disrupted citrus IPM in southern California, in particular, Temecula in Riverside County. A similar situation of preemptive spraying in citrus has developed in the Central Valley, especially in Tulare County.to mitigate GWSS migration into grapes. Consequently, pesticide usage has increased substantially in vineyards to kill invading GWSS that survived citrus sprays or migrated in from untreated wilderness and residential areas. GWSS is the subject of a major classical biological control program in California. Mymarid egg parasitoids from the home range of GWSS in southeastern USA are being imported and released in California in an attempt to control inordinate pest densities. Two new parasitoid species previously lacking in California have been imported over the last two years Gonatocerus triguttatus from Texas and G. fasciatus from Louisiana. It is likely that G. triguttatus has established in southern California, as this parasitoid has been recovered from different release sites several times. It is unknown whether G. fasciatus, which was released last year, has established. These two parasitoids join the resident G. ashmeadi, a parasitoid with a geographic range that includes Florida through eastern Texas. G. ashmeadi is most likely not native to California and was probably introduced with GWSS in the early 1990s and may have established on eggs of H. liturata, a native California sharpshooter. The research proposed in this grant is essential for the long-term management of the GWSS-PD epidemic because imported biological control agents are expected to play a fundamental role in the permanent suppression of GWSS populations that vector PD. Consequently, management decisions for GWSS that are reliant on combined components of biological, cultural, or chemical control strategies as part of an IPM program will require information on the basic biology, ecology, and behavior of imported Gonatocerus spp. Maximal exploitation of imported natural enemies, effective management, conservation, and mass rearing of mymarid parasitoids for GWSS suppression will require information that can only be attained if comprehensive studies of the biology, behavior, and impact of the three Gonatocerus spp. alone and in combination are made. Therefore we aim to achieve as quickly as possible a thorough understanding of what we consider to be the most important aspects of Gonatocerus spp. ecology, biology and behavior to maximize the role of biological control for GWSS suppression. Our research objectives have been designed to achieve this rapid understanding.
• Publication Date: Aug 2003
• Journal: 2003 Pierce's Disease Research Symposium