Insect Management in Non-Bt Cornfields

The introduction of corn hybrids that express insect-toxic proteins from genes transferred from the soil bacterium Bacillus thuringiensis (i.e., Bt corn hybrids) significantly altered corn production in much of North America, and specifically changed perspectives about insect management. The exceptional efficacy of Bt corn against European corn borer has essentially eliminated this once-most-important corn pest to non-pest status in Bt corn fields. Bt corn targeted for control of corn rootworm larvae was also so effective that it changed the way growers manage corn insects, in general. However, the development of resistance to Bt proteins in some western corn rootworm populations and the typically higher cost of Bt corn compared with non-Bt corn have motivated some producers to grow non-Bt corn hybrids again. Consequently, we now need to revisit fundamental insect management strategies and tactics for non-Bt corn, including scouting techniques and reference to economic thresholds. Growers and advisers with little or no point of reference about the potential threat posed by European corn borer (they’re still out there, surviving on many other hosts) and about managing corn rootworms without Bt corn hybrids will benefit from this overview.