Crystal proteins from Bacillus thuringiensis subsp. thompsoni strain HnC are active against the codling moth, Cydia pomonella, a major pest of orchards. Inclusion bodies purified from strain HnC displayed an LC50 of 3.34 x 10(-3) mu g/mu l. HnC-purified crystals were tenfold more active than Cry2Aa and Cry1Aa toxins, and 100-fold more toxic than Cry1Ab. The 34-kDa and 40-kDa proteins contained in HnC inclusion bodies were shown to act synergistically. The toxicity of crystal proteins produced by the recombinant B. thuringiensis strain BT-OP expressing the full-length native operon was about tenfold higher than that of the 34-kDa protein. When the gene encoding the non-insecticidal 40-kDa protein, which is not active, was introduced into the recombinant strain producing only the 34-kDa protein, the toxicity was raised tenfold and was similar to that of the strain BT-OP.