Relative toxicity of Bacillus thuringiensis var. tenebrionis to the two-spotted spider mite (Tetranychus urticae Koch) and its predator Metaseiulus occidentalis (Nesbitt) (Acari, Tetranychidae and Phytoseiidae)
Authors: Chapman, M.H., Hoy, M.J.
Journal, Volume, Year: Journal of Applied Entomology, volume 111:147-154, 1991
Wettable powders from Btt were tested at field application levels for their toxicity to two-spotted spider mites and its predator mite. There was relatively little effect on survival of the spider mite but there was only 26% survival of the predator.
They did not use transgenic Bt. This study did show toxicity to a beneficial predator.