Characterizing the activity of Vip3A against fall armyworm (Lepidoptera: Noctuidae) in field corn and cotton

Fall armyworm remains an important pest in Southern U.S. cropping systems due to the natural tolerance of this insect to widely-used Bacillus thuringiensis (Bt) Cry proteins, as well as its resistance to many classes of insecticides used in traditional IPM programs. Syngenta Crop Protection has recently registered a new and different Bt protein, known as Vip3A, whose unique mode of action has the potential to improve efficacy against target insects and to broaden the spectrum of pests controlled. The objective of these experiments was to evaluate the insecticidal effects of Vip3A expressed in corn and cotton plants against fall armyworm. Two corn lines, one expressing the Viptera (Vip3A + Cry1Ab) trait and another conventional non-Bt control, were planted in field trials. Plants (V8-V10 stages) were infested with ten 2nd-instars and evaluated for injury 14 d after infestation (DAI). Ears (10-15 cm green silk stage) on other plants were infested with a single 2nd instar on each ear and evaluated for injury at 7 DAI. Damage on Viptera leaf tissue and ears was significantly lower than that on the non-Bt control. Similar tests were performed on VipCot (Vip3A + Cry1Ab) and conventional non-Bt cotton lines. Third instars of fall armyworm were caged on cotton fruiting structures (squares, white flowers, and bolls) during reproductive stages of plant development. Larval survivorship and fruiting form injury were evaluated at 2-3 DAI and 5-6 DAI. Survivorship and damage across all structures was significantly lower on VipCot than that on the non-Bt control.