ABSTRACT
When pesticides are used, this pest-yield interaction and interactions with other agronomic factors are always important and make evaluation of agronomic response and economic benefit difficult. Cereal crops respond to pesticides in many ways. Herbicide effects on plant disease potential has been reviewed by J. Altman and C. L. Campbell, and herbicide interaction with soil-borne disease organisms is documented. The impact of soil-borne and foliar diseases was measured using various types and combinations of fungicides. Pesticide decision aid models incorporate yield potential, pest potential, and crop management practices to predict responses. The agrichemical industry and growers can alleviate some of these problems by using pesticides on an as-needed basis, better timing of applications, targeting specific pests, and developing materials with low environmental impacts. External costs are highly variable and difficult to quantify, but often increase as cropping intensity increases. Economic returns were based on yield response and 1988 input and return costs.
