Toxic Effects of Bt-(Cry1Ab+Vip3Aa) Maize (“DBN3601T’’ Event) on the Asian Corn Borer Ostrinia furnacalis (Guenée) in Southwestern China

Asian corn borer (ACB), Ostrinia furnacalis, is an important agricultural pest affecting maize production in southwestern China, but knowledge of the toxic effect of Bt maize on the pest has been insufficient until now. In this study, we determined the susceptibility of ACB to Cry1Ab, Vip3Aa, and their complex proteins and evaluated the efficacy of Chinese domestic Bt-(Cry1Ab+Vip3Aa) maize (“DBN3601T” event) against the pest in Yunnan Province of southwestern China. The susceptible bioassay indicated that the LC50 values of the Cry1Ab and Cry1Ab+Vip3Aa proteins expressed by the Bt maize varieties against ACB larvae were 51.42 and 46.85 ng/g, respectively; however, the ACB larva was insensitive to the Vip3Aa protein. The Cry1Ab+Vip3Aa protein contents in V6–V8 leaves, VT tassels, R1 silks, R2 kernels, R3 stalks and R3 cobs of the Bt-(Cry1Ab+Vip3Aa) maize were 114.20, 30.69, 3.77, 8.92, 11.09 and 10.99 μg/g, respectively. The larval feeding test indicated that the Bt-(Cry1Ab+Vip3Aa) maize was more toxic to the early instar larvae, and the survival time of larvae fed on the leaves was the shortest, while it survived the longest on stalks. The identification of maize resistance levels in the field showed that both larval density and plant damage score of Bt-(Cry1Ab+Vip3Aa) maize were significantly lower than those in conventional maize. It is concluded that the Bt-(Cry1Ab+Vip3Aa) maize can be used for control of the ACB in southwestern China.