Evaluating the use of soil applied microbial products to control overwintering olive fruit fly, Bactrocera oleae, in CA orchards

Olive fruit fly, Bactrocera oleae is the most important insect pest of California olives and a serious pest throughout most olive growing regions of the world. Fruit infestation can reach 100 percent if not treated. An estimated 63 percent of olives grown in California are susceptible to OLF with potential losses of over $120 million. OLF is primarily managed with a single product, GF-120 spinosad bait, for which resistance is well documented. Bactocera oleae overwinter as pupae in soil and emerge as adults in the spring. We evaluated the use of the insect pathogenic fungi, Beauveria bassiana and Metarhizium anisopliae, that are commercially available as a control for overwintering B. oleae. We conducted lab bioassays and field studies to determine the efficacy of the fungi against B. oleae. Our findings suggest that B. oleae emerging adults are more susceptible to the fungi than larvae and pupae. We also found that B. bassiana and M. anisopliae can persist in CA orchard soil for at least two months when applied in the fall. The potential use of B. bassiana to manage B. oleae will be discussed.