Toxicity of the β-exotoxin of Bacillus thuringiensis to Tetranychus pacificus and Metaseiulus occidentalis (Acari: Tetranychidae and Phytoseiidae)

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Abstract
The β-exotoxin of B. thuringtensis (thuringiensin) was toxic to adult female Tetranychus pacificus (McGregor) and Metaseiulus occidentalis (Nesbitt) within 48–96 h when they were treated at rates from 0.125- to 4-fold the proposed field rate. Egg production by treated females of both species declined within 48 h. Treated larvae were unable to develop to adults. Treated eggs hatched, but larvae of both M. occidentalis and T. pacificus failed to develop. Thuringiensin is an effective but, at these rates, unselective acaricide. Because intrinsic selectivity is not present at the proposed field rates, selectivity will have to be achieved through other means if the product is to be incorporated into integrated pest management programs in which this predator is important.