2002-2004 Specialty Crops Research Program
University of California

Principal Investigators: Kent Daane, Marshall Johnson, Russell Messing and Kim Hielmer

Project title: Importation and host range testing of parasitoids that attack the Olive Fruit Fly, Bactrocera oleae

The olive fruit fly (OLFF), Bactrocera oleae, has recently invaded California, spread rapidly throughout the state, and poses a serious threat to the economic well-being of the olive industry. Insecticidal control, even if effective, will be costly, and potentially environmentally harmful and disruptive of existing ecological relationships among arthropods within olive agro-ecosystems. Classical biological control via the importation of natural enemies that attack and kill the OLFF has the potential to contribute substantially to safe and effective management of this invasive pest. Biological control will be particularly important in the suppression of flies in abandoned orchards and residential areas where olives are used as ornamentals. These trees serve as important sources for reinfestation of commercial olives.

The OLFF is believed to be native to sub-Saharan Africa, or possibly southwest Asia. We propose to conduct explorations and collections in these areas to obtain co-evolved natural enemies that attack OLFF, and closely related flies, and to import these species into laboratories in France, California, and Hawaii. In quarantine, the parasitoids will be studied to determine the range of fruit fly species that are attacked, including invasive pest species, endemic non-target species, and beneficial tephritid species that are used in biological control of weeds. We will also determine basic bionomic and behavioral parameters of the parasitoids such as longevity, fecundity, and oviposition sequences.

In addition to novel natural enemies, we will conduct detailed evaluations of parasitoid efficacy for several species that are already available in laboratory cultures in Hawaii. These include (but are not limited to) Psyttalia concolor, an African wasp that has been experimentally used in Europe in augmentative releases against OLFF; and Fopius arisanus, a very effective egg parasitoid from southeast Asia that has recently been shown capable of utilizing OLFF as a suitable host. Several additional parasitoids of fruit flies from Asia and Australia are also available for testing. We will quantify host-habitat finding, host finding, host suitability, and host regulation of these species when caged with OLFF.

Pending documentation of safety (in terms of an adequately limited host range), we will apply for permits to release suitable natural enemies in olive orchards throughout California, and will conduct follow-up studies both to assess their efficacy and to confirm the absence of significant non-target side effects. We will train extension workers to identify and understand the role of the parasitoids in OLFF control, and how best to integrate them into pest management programs in commercial olive orchards throughout the state. We will integrate new information on native and imported natural enemies with ongoing research programs on chemical and cultural controls of this important pest.