Prevalence of Early- and Late-Season Pest Damage to Corn in Cover Crop-Based Reduced-Tillage Organic Systems.

Abstract

In organic agronomic cropping systems, the use of synthetic insecticides and transgenic varieties are prohibited and producers rely mainly on biological control, tillage, crop rotation, and other cultural practices to manage pests. We measured damage to organic corn (Zea mays L.) from multiple invertebrate pests, including slugs (Gastropoda: Mollusca), European corn borer (Ostrinia nubilalis Hübner), corn earworm (Helicoverpa zea Boddie), and fall armyworm (Spodoptera frugiperda Smith), early and late in the growing season in four cropping systems that varied in tillage frequency and intensity and in winter cover crop species. Specific management tactics included two cover crop mixtures preceding corn, the use of a roller-crimper or tillage to terminate cover crops preceding corn, and the establishment of interseeded cover crops after corn emergence. Prevalence of early-season damage was high, but severity of damage was very low and unrelated to corn yield. The proportion of corn plants affected by chewing pests early in the season was lower in plots in which tillage compared to a roller-crimper was used to terminate cover crops. Cropping system did not affect the numbers of late-season caterpillar pests or corn yield. Predation by natural enemies appeared to effectively maintain damage from chewing pests below yield-damaging levels. These results support the inclusion of winter and interseeded cover crops in organic agronomic crop rotations to gain environmental benefits without increasing risks of damage by insect pests.