Evaluation of Bacillus thuringiensis as a biocide of blackfly larvae (Diptera: Simuliidae)

Thirteen strains of Bacillus thuringiensis were bioassayed against late-instar larvae of field-collected Simulium vittatum. All 13 strains caused significant blackfly mortality. The mortalities ranged from 64% for the HD 225 strain to 88% for HD 39 at 10 ppm for a 24-hr exposure period. A minimum 24 hr of exposure to a minimum concentration of 10 ppm was required to produce mortalities approximating 90%. The LC₅₀ values for the HD 39 and HD 225 strains were 1.1 and 1.0 ppm, respectively.