Soil-Management History and the Role of Plant Mineral Balance as a Determinant of Maize Susceptibility to the European Corn Borer

Abstract

Proponents of organic farming have long suggested that their methods produce “healthy” crops that are less susceptible to insects and diseases. Experimental comparisons of European corn borer (ECB) egg-laying response to maize plants grown in a greenhouse in soil collected from either organically or conventionally managed farms provided evidence consistent with these assertions. In each of three paired comparisons, higher egg-laying occurred on plants in conventional soil. Subsequent studies suggested that differences in ECB ovipositional preference were related to plant-mineral balance; a three-mineral quadratic model showed strong predictive power for ECB oviposition. A role for plant minerals was also suggested in a study of paired maize fields with high and low ECB populations compared at three different geographic locations. Significant differences in leaf-mineral profiles between fields were measured that were consistent across locations. Based on these cumulative findings, it is hypothesized that: (1) maize plants with an optimal mineral balance show lower susceptibility to insect pests, (2) determining the effects of minerals on susceptibility must include consideration of both ratios and absolute levels, and (3) a more resistant physiological state is more likely in organically managed soils because of the inherent greater capacity of these soils to buffer availability of minerals to plants.