Pupal mortality and adult emergence of western cherry fruit fly (Diptera: Tephritidae) exposed to the fungus Muscodor albus (Xylariales: Xylariaceae).

Western cherry fruit fly, Rhagoletis indifferens Curran (Diptera: Tephritidae), is a major pest of sweet cherry, Prunus avium (L.) L. (Rosales: Rosaceae), that is conventionally controlled using insecticides. One alternative to the use of insecticides alone for fly control could be fumigation of the fly's overwintering habitat using the fungus Muscodor albus Worapong, Strobel & Hess (Xylariales: Xylariaceae) in conjunction with reduced insecticide use. The fungus produces a mixture of volatile organic compounds (VOCs) that are biocidal for a variety of organisms. In this study, the main objectives were to determine the effects of M. albus VOCs on mortality of R. indifferens pupae and on adult emergence under laboratory conditions. In fumigation chamber experiments, a 14-d exposure of pupae in soil to VOCs resulted in 61.9% control, and exposure to VOCs for 7, 10, and 14 d reduced fly emergence by 44.2, 70.0, and 86.3%, respectively, relative to controls. In an experiment using plastic covers to retain VOCs in treated soil, a concentration of 1% M. albus formulation (fungus + rye grain) did not affect pupal mortality and fly emergence, but a concentration of 5% M. albus formulation resulted in 27.4% control and reduced fly emergence by 30.1% relative to the control. Larvae of R. indifferens that were dropped onto soil with 1% M. albus formulation were not affected by the fungus. Results indicate that prolonged exposure and high concentrations of M. albus VOCs can cause significant mortality of R. indifferens pupae in soil and delay adult emergence.