Effects of varying weed communities in corn on European corn borer, Ostrinia nubilalis (Hubner) (Lepidoptera: Crambidae), oviposition, and egg mass predation

Recent advances in weed control technology have changed how vegetational diversity can be managed in agroecosystems. This 2-yr study assessed the impact of altering the timing of herbicide application in herbicide-resistant field corn on the European corn borer, Ostrinia nubilalis (Hubner), and on the beneficial insects that prey on O. nubilalis egg masses. Treatments in this study were intended to allow weed presence in the field for varying periods of time, but control the weeds before crop yield was negatively impacted. Effects on O. nubilalis oviposition were assessed directly by counting egg masses and indirectly by assessing damage to corn stalks resulting from O. nubilalis infestations. The impact of weeds on the main generalist predators in this system was quantified through direct counts and predation trials on sentinel egg masses. In this study, altering the timing of herbicide application in herbicide-resistant field corn did not appear to affect the oviposition preference of O. nubilalis or the beneficial insects that prey on its egg masses. End-of-season stalk comparisons showed no differences in O. nubilalis infestation levels among the treatments. Predation on sentinel egg masses showed few significant differences among treatments, and predator densities were only rarely significantly different by treatment and showed no evident trends. Thus, our data suggest that under the conditions of this experiment, manipulating herbicide applications to minimize O. nubilalis damage is not a viable management technique in field corn.