Laboratory Evaluation of an Exotoxin from Bacillus thuringiensis Subsp. morrisoni to Horn Fly Larvae (Diptera: Muscidae) and Mice1

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Abstract
Exotoxin from culture supernatant of Bacillus thuringiensis subsp. morrisoni was prepared using Sephadex G-25-40 columns. The toxin was determined to be β-exotoxin by high performance liquid chromatography methods. In bioassays against larvae of the horn fly, Haematobia irritans (L.), the LC50 and LC90 were estimated to be 2.79 and 8.03 μg/g larval medium, respectively. Maximum mortality of horn fly larvae peaked at 98% when the feces of an animal treated with 3.0 g per day for 5 days was bioassayed. When white mice were treated by subcutaneous injections, the LD50 was 184.8 and 135.6 μg/g body weight for males and females, respectively.