Within-field Spatial Variation of Northern Corn Rootworms

Sampled distributions of pest populations usually are considered as a field mean for the density of insects per unit area or per sample unit for a given field. In reality, the actual distributions vary spatially at any given moment, that is, they are not constant over the entire expanse of a field. Spatial variability in rootworm incidence suggests that a site-specific approach to the management of corn rootworms may be feasible. This concept is attractive because of the environmental benefits from possible reduction in pesticide usage and lower input costs for the grower. Dispersion of a pest also may change through time as the population develops. This temporal variability makes precision corn rootworm management difficult to undertake. Intensive grid-sampling provides potentially valuable knowledge in GIS-managed data layers concerning rootworm distribution in relation to soil properties, fertility, weeds, landscape, and yields in corn fields, but the usefulness of the information is limited by problems related to implementing precision farming programs for corn rootworms. The necessary GIS/GPS capabilities are available but have not yet been effectively combined into systems incorporating map-driven application technology with economical scouting methods or real-time monitoring and mapping of corn rootworm variability