Disclosed is a novel cadherin peptide that enhances the toxicity of Cry proteins. A novel insecticide composition comprising an effective amount of cadherin peptide having SEQ. ID. NO:2 and an effective amount of Bacillus thuringiensis Cry protein wherein the cadherin peptide comprises a Cry3Aa toxin binding region from the full-length T. molitor cadherin and has synergistic characteristics of a binary toxin potentiating Cry3 and Cry1 toxins against coleopterans and lepidopteran species, respectively