Mortality of Different Life Stages of Rhagoletis indifferens (Diptera: Tephritidae) Exposed to the Entomopathogenic Fungus Metarhizium anisopliae

Effects of the entomopathogenic fungus Metarhizium anisopliae (Metschnikoff) Sorokin on the mortality of different life stages of the western cherry fruit fly, Rhagoletis indifferens Curran (Diptera: Tephritidae), were determined in laboratory tests. When teneral adults were exposed to fungal spores mixed in soil (7.63 × 10⁵ and 1.61 × 10⁶ spores/g) or applied to the surface of soil (1.14 × 10⁶ and 2.28 × 10⁶ spores/cm²) with 13 to 30% moisture, adult emergence was not reduced, but 14.9 to 68.0% of emerging adults were infected at death. When adult flies were exposed to various concentrations of dry spores inside vials, 15 mg (4.59 × 10⁸ spores/10 flies) was the lowest needed for 100% mortality at 7 d post exposure, and resulted in 5.96 × 10⁶ spores adhering to each fly. Females exposed to 1.80 mg (5.51 × 10⁷ spores/10 flies) laid as many eggs as control females between 0 and 3 d post exposure, but due to mortality infected flies laid fewer eggs between 3 and 7 d. Third-instar larvae exposed to treated soil (9.63 × 10⁴ to 4.81 × 10⁶ spores/cm²) with 20% moisture were not infected.