Mechanisms involved in nontarget effects of pesticides on soil-borne pathogens

The effective control of diseases, pests, and weeds constitutes one of the major contributions to the increase of yield and quality of agricultural products of the last decades. The role of crop protection chemicals in this development is well recognized; in areas with intensive agriculture, most crops receive one or more applications of several crop protection products during one growing season. Although much effort is made to confine the activity of the products to the target organisms, the desired specificity has been achieved for only very few products, like those acting as antipenetrants against fungal patho-gens. 1 Most side effects are detrimental to the nontarget organisms or their functions, but from the viewpoint of agronomy a few effects are considered as beneficial, e.g., those resulting in conservation of nitrogen in fumigated fields.