Bacillus thuringiensis Cry3Aa toxin increases the susceptibility of Crioceris quatuordecimpunctata to Beauveria bassiana infection

The spotted asparagus beetle, Crioceris quatuordecimpunctata (Coleoptera: Chrysomelidae), is one of the most devastating pests of asparagus in China. Sprayed synthetic pesticides have been used to control C. quatuordecimpunctata damage, but they pose problems because of residues and harm to natural enemies. Neither the microbial coleopteran-specific toxin from Bacillus thuringiensistenebrionis, Cry3Aa, nor the fungal pathogen Beauveria bassiana have sufficient activity to effectively control C. quatuordecimpunctata damage to asparagus. However, second instar C. quatuordecimpunctata larvae exposed to a sublethal dose of Cry3Aa toxin demonstrated significantly higher larval mortality when exposed to B. bassiana. Our results suggest that a combination of Cry3Aa and B. bassiana may be effective in reducing damage by C. quatuordecimpunctata larvae to asparagus.

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► The LC50 of Cry3Aa toxin for second instar spotted asparagus beetle is 30× that for neonates.
► Low dose Cry3Aa reduces Crioceris quatuordecimpunctata larval weight and slows growth.
► Sublethal Cry3Aa synergizes Beauveria bassiana toxicity toward C. quatuordecimpunctata.