The Importance of Reporting Soil Properties in Insecticide and Acaricide Tests and Methods of Determination

A large number of tests are performed annually to evaluate the efficacy of chemicals for controlling plant pathogenic microorganisms and insects in the soil. Many of these testsare reported with minimal or no reference to soil conditions. Yet, the soil can have profound effects on the efficacy of a chemical in two major ways: 1) it can affect the susceptibility of a organism to the chemical and 2) it can have a direct effect on the toxicological properties of the chemical (10). For example: Most organisms, to varying degrees, are less sensitive to toxicants when in a dormant or resting state which is often encouraged by unfavorable soil conditions such as cold temperature, drought, and flooding. Also, soils are very reactive chemically and physically. Many chemicals are adsorbed or absorbed on soil particles such as clay and organic matter and thus may become inactivated. In other cases, the soil structure, texture, temperature and moisture may limith the dispersal of the toxicant throughout the plow layer from the point of application; this is especially critical with fumigant type products. The soil pH can have a marked influence on the toxicity of the chemical.