Hybrid and nitrogen source affect yield and European corn borer damage

Transgenic corn plants that contain cry proteins (Cry1Ab, Cry1Ac, and Cry9C ) of Bacillus thuringiensis (Bt) offer corn (Zea mays L.) growers a more pr actical and environmentally friendly solution to manage European corn borer (ECB) (Ostrinia nubilalis Hubner) induced loss. Bt corn has demonstrated s uch promising initial results that it may be susceptible to ECB resistance from overuse. The objective of this study was to investigate nitrogen (N) s ource effects on ECB damage on continuous corn yield. The effects of N sour ce on soil NO3--N, plant height, 2nd generation ECB damage, and gl ain yiel d were investigated on a Quakertown silt loam (Fine-loamy, mixed, mesic, Ty pic Hapludult) from 1995 to 1998. Based on ECB damage observations in 1995 and 1996, plots were split in 1997 and corn isolines were evaluated to stud y the ECB and yield response to Bt corn. Corn yield did not respond to manu re plus sidedress N over the 4-yr period of this study because soil N level s were adequate without sidedress N, as indicated by the pre-sidedress nitr ate test (PSNT). Second generation ECB damage was greater in manure plots i n all 4-yr. In 1997, an outbreak year, and 1998, an endemic year, Bt corn a nd manure yielded 19 and 7% greater than non-Bt corn and manure. Our findin gs suggest that Bt corn is of significant value on land receiving manure in continuous corn production where ECB damage is high.