Toxicity of Activated Cryl Proteins from Bacillus thuringiensis to Six Forest Lepidoptera and Bombyx mori

The insecticidal activity of the CryIB, CryIC, CryID, and CryIE δ-endotoxin proteins from Bacillus thuringiensis was investigated in force-feeding experiments with larvae of Choristoneura fumiferana, Orgyia leucostigma, Lymantria dispar, Malacosoma disstria, Lambdina fiscellaria fiscellaria, Actebia fennica, and Bombyx mori. The toxins were prepared by proteolytic activation of protoxins expressed in Escherichia coli and quantified by scanning densitometry after separation on sodium dodecyl sulfate-polyacrylamide gels. All toxins retained full insecticidal activity during 7 months of refrigerator storage at pH 10.5. The most sensitive response was recorded for B. mori, the only species that exhibited sufficient mortality at generally