The olive fruit fly (Bactrocera oleae (Gmelin)) in California: Phenology, cultivar preference, and reproductive biology

The olive fruit fly (Bactrocera oleae (Gmelin)) is an invasive pest of olives in California. This invasion represents the first declared establishment of an exotic fruit fly in California and poses a serious threat to the table and oil olive industries. B. oleae population dynamics and reproductive biology were monitored from 2002 through 2006 in order to determine the insect's phenology at diverse California locations. Peak B. oleae activity was observed in spring and fall throughout the state but was delayed until fall at coastal locations. Four to five annual generations were observed, three occurring during the olive production season, May through December, and one to two occurring in winter spring. Female B. oleae reproductive maturity was positively correlated with both trap captures and fruit infestation. Mean egg load and the proportion of reproductively mature female flies decreased in the spring, a phenomenon also observed in Europe. Three commercially available monitoring traps for B. oleae were tested at three sites in California. In all cases where significant differences were found among traps, McPhail traps captured more flies than all other trap types. Female B. oleae exhibit strong ovipositional preference for certain varieties of the domesticated olive, Olea europaea L. This preference was observed in the field, and laboratory assays were conducted to evaluate larval performance. Sevillano, Manzanillo, and Mission olives were the most heavily infested varieties in the field. Pupae developing in Manzanillo and Sevillano olives weighed more than those developing in less preferred varieties, and, larval developmental time was significantly shorter in Sevillano olives. Larval B. oleae densities tracked in the field at six locations were found to be highly variable and related to overall fly infestation and adult densities. Olive fruits were infested at different densities in the laboratory, and at the highest egg density, all measures of performance were negatively impacted, resulting in fewer and lighter pupae that took longer to pupate and emerge as adults. This research has described the biology of B. oleae in its expanded range and suggests areas of further study.