BT Corn Performance Against First- and Second-Generation Infestations of European Corn Borer, 1997

Abstract

Abstract Six transgenic corn hybrids expressing insecticidal proteins produced by genes from Bacillus thuringiensis (Bt) were evaluated at the Rosemount Experiment Station in separate experiments that targeted first and second generations. The hybrids representing 5 different insertion events, and their non-Bt isolines were evaluated in a RCB design with tour replications. Test hybrids were planted in the center 2 rows of a 4-row plot (22 ft long, 30-inch row spacing). Border rows were planted to NK 4640Bt to preclude inter-plot movement of larvae. Plots were planted on 21 May using a cone planter and thinned to 30,000 plants/A. In view of extensive natural first generation infestation, the second-generation experiment was treated with Warrier 1 E (zeta cypermethrin) @ 3.8 fl oz/acre on 15 Jul. In each plot, 15 consecutive plants were tested for Bt expression and non-expressers were rogued on 29 Jul. The plants intended for first generation evaluation were infested at the V6 with neonate larvae in grits deposited in the whorl on 14 Jul. Heavy natural egg laying from second generation eliminated the need for manually infesting second-generation plots. First generation evaluations included: number and length of tunnels on 21 Aug and % of plants with leaf injury and a leaf injury rating on 24 Sep. On 9 Oct the second generation measurements were recorded: number of overwintering larvae, tunnel number and length, and shank and ear damage.