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Olive fruit fly, Bactrocera oleae (Rossi) (Diptera: Tephritidae), is the major pest of commercial olives worldwide. Various aspects of its biology, ecology, management, and impact on olive production are highlighted. With the discovery of insecticidal resistance in some populations frequently treated with organophosphates, old and new control options are being investigated. The potential of biological control is examined. Surveys suggest that a small group of braconids in the Opiinae subfamily best represent the primary parasitoids attacking olive fruit fly in its native range. These species include Psyttalia lounsburyi, P. dacicida, P. concolor, P. ponerophaga, and Utetes africanus. Bracon celer, another braconid but in the Braconinae subfamily, is also reared from the fruit fly in its native range. The potential of these and other natural enemies is discussed with respect to olive fruit fly biology, commercial olive production, and biological constraints that may limit their success. We suggest that numerous species exist that should be further investigated as control agents for olive fruit fly in the many climatic regimes where the pest is found.

Continued success of the most widely used MATERIALS AND METHODSInsects. We studied P. xylostella from 13 laboratory colonies derived from individuals collected at eight field sites in Hawaii (11,25). Larvae were fed cabbage foliage and colonies were maintained at 280C as described (25). The LAB-P colony, which was not exposed to B.t., served as the primary reference susceptible colony (26).We investigated the stability of resistance to B.t. in six laboratory colonies that were started from a field population (called NO) from Oahu, HI. The NO population had been treated repeatedly with B.t. in the field (11) and had developed moderate resistance to Dipel, a wettable powder formulation of a crystal-spore mixture of B.t. subspecies kurstaki (27,28). In the first laboratory-reared generation (F1), the LC50 (concentration required to kill 50% ofinsects tested) of NO larvae was about 25 times greater than the LC5o of larvae from the susceptible LAB-P strain (11). The NO colony was reared without exposure to B.t. for 3 generations, and then it was split into four colonies: NO-P, NO-Q, NO-R, and NO-U (23). NO-P, NO-Q, and NO-R were selected for additional resistance (see ref. 23 and description below) and then, as part of the present study, were reared without exposure to B.t. to examine the stability of extremely high resistance. To examine the stability of moderate resistance, NO-U was maintained without any additional exposure to insecticide for 35 generations. Results from the first 15 generations of rearing NO-U without exposure to B.t. were reported in detail previously (23) and are summarized here for comparison with results from NO-P, NO-Q, and NO-R. Selection and Reselection Experiments. NO-P, NO-Q, and NO-R were selected for additional resistance by feeding Abbreviations: B.t., Bacillus thuringiensis; ICP, insecticidal crystal protein; AI, active ingredient. tTo whom reprint requests should be addressed. 4120The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.

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