EFFICACY OF BEAUVERIA-BASSIANA FOR CONTROLLING THE HOUSE-FLY AND STABLE FLY (DIPTERA, MUSCIDAE)

Two strains of Beauveria bassiana (Balsamo) Vuillemin (P89 and L90) we re evaluated for pathogenicity to adult and larval house flies, Musca domestica L., and the adult stable fly, Stomoxys calcitrans (L.). B. b assiana conidia formulated as a dust or aqueous solution were applied to plywood surfaces. Adult flies of both species were exposed to the t reated plywood surfaces for 3 h. House fly mortality was dose dependen t, with greater than or equal to 90% dying at 1 x 10(8) conidia/cm(2) (high dose) for strains P89 and L90 formulated as dusts. Stable flies were not as susceptible as house flies to either pathogen strain. In s imilar experiments, a high dose of 1 x 10(8) conidia/cm(2) 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 x 10(7) conidi a/Cm-2) and low doses (1 x 10(6) conidia/cm(2)) for both species of fl ies. Aqueous formulations were less effective for controlling both spe cies of adult flies than for dust formulations. B. bassiana lost patho genicity over time and plywood treated 28 days before host exposure re tained little residual effect on flies. In larval bioassays, B. bassia na was most effective against the house fly at 1 x 10(10) conidia/cm(3 ), at which 56 and 48% of the house fly larvae died following a high-d ose treatment with strains L90 and P89, respectively. A dose response also was observed for the medium (1 x 10(9) conidia/cm(3)) and low dos es (1 x 10(8) conidia/cm(3)). (C) 1995 Academic Press, Inc.