Biological control of olive fruit fly

Abstract: The establishment and spread of olive fruit fly (OLF), Bactrocera oleae (Rossi),among olive production areas of California, USA, stimulated the initiation of a classicalbiological control project focused on the discovery introduction, and establishment of effectivenatural enemies to maintain OLF populations at non-injurious levels. Biological control was thepreferred control tactic for OLF because of its potential long-term sustainability and low risk tohuman health and the environment. Factors influencing the potential success of this programwere reviewed. Parasitoid natural enemies were sought in areas of Africa, the MediterraneanBasin and parts of Asia where various subspecies of olive, Olea europaea L., have grown forthousands of years. Molecular studies helped distinguish original areas of evolution of the OLF,identify natural enemies and separate parasitoid sibling species and geographic strains. To ensurelow potential of non-target environmental impacts, the host specificities of candidate naturalenemies were evaluated relative to attack and reproduction on various tephritid fly speciesincluding some that are beneficial biological control agents of weeds. Increases in olive fruit size,via domestication, reduced natural enemy effectiveness by producing natural enemy-free spacewithin the olive fruit. The ultimate success of this program will be determined by the candidateparasitoids’ abilities to adapt to the widely varying climatic conditions within California.Presently, the program is in the introduction and colonization phases with some field recovery ofreleased parasitoids experienced to date.