VIRULENCE OF DIFFERENT ISOLATES AND FORMULATIONS OF BEAUVERIA-BASSIANA FOR HOUSE-FLIES AND THE PARASITOID MUSCIDIFURAX RAPTOR

Adult house flies (Musca domestica) were susceptible (94-100% mortalit y) to Beauveria bassiana when conidia of the Hf88 isolate were applied to plywood boards at 10(7) conidia/cm(2); a starch dust formulation w as more effective than a liquid suspension. Adult flies were also susc eptible (90-99% mortality) to this isolate when they were con fined wi th treated water (10(8) conidia/ml) or food (10(8) conidia/100 mg). Ho use fly larvae were not affected by treatments with up to 10(8) conidi a/cm(3) of rearing medium. A 2-year survey of house flies cm from New York dairies indicated that most natural infections of house flies occ urred in September and October, although prevalence rates never exceed ed 1%. Thirteen single-fly isolates obtained during this survey were c ompared with the Hf88 isolate for virulence against flies; the 2 most virulent isolates were slightly more virulent for flies than for the f ly parasitoid Muscidifurax raptor. Incorporation of conidia into a suc rose bait (10(8) conidia/100 mg) in cages gave high levels of house fl y control (78-100% mortality) 5 days after exposure. (C) 1995 Academic Press, Inc.