Efficacy of Beauveria bassiana for Controlling the House Fly and Stable Fly (Diptera: Muscidae)

Two strains of Beauveria bassiana (Balsamo) Vuillemin (P89 and L90) were evaluated for pathogenicity to adult and larval house flies, Musca domestica L., and the adult stable fly, Stomoxys calcitrans (L.). B. bassiana conidia formulated as a dust or aqueous solution were applied to plywood surfaces. Adult flies of both species were exposed to the treated plywood surfaces for 3 h. House fly mortality was dose dependent, with ≥ 90% dying at 1 × 108 conidia/cm2 (high dose) for strains P89 and L90 formulated as dusts. Stable flies were not as susceptible as house flies to either pathogen strain. In similar experiments, a high dose of 1 × 108 conidia/cm2 killed only 70 and 84% of the adult stable flies exposed to strains P89 and L90, respectively. A dose response was evident for medium (1 × 107 conidia/cm2) and low doses (1 × 106 conidia/cm2) for both species of flies. Aqueous formulations were less effective for controlling both species of adult flies than for dust formulations. B. bassiana lost pathogenicity over time and plywood treated 28 days before host exposure retained little residual effect on flies. In larval bioassays, B. bassiana was most effective against the house fly at 1 × 1010 conidia/cm3, at which 56 and 48% of the house fly larvae died following a high-dose treatment with strains L90 and P89, respectively. A dose response also was observed for the medium (1 × 109 conidia/cm3) and low doses (1 × 108 conidia/cm3).