Evaluation of Adjuvant Modes of Action: A Theoretical Approach

Abstract

Many products are available commercially as tank-mix or built-in adjuvants for improving the efficiency of various stages in the application of pesticides to foliage (recent reviews by Chapman and Mason 1993; Foy 1993; Holloway 1993). Because most adjuvants are usually sold for a specific purpose it is often taken for granted that their modes of action are well understood. However, this is the exception rather than the rule, since in many cases successful products have evolved mainly from extensive but empirical screening, especially for beneficial effects on the biological activity of pesticides. From the point of view of marketing and labelling of adjuvants, it is important for the end-user to have basic information on how a particular adjuvant works so that he can assess its relative merits and usefulness for a crop protection programme. For this to be achieved reliable quantitative methods for evaluating performance and activity are required both in the laboratory and in the field. In the past such an approach has not been given sufficient priority by the industry, which as a result has been tarnished by a ‘snake oil’ and ‘spray-and-pray’ image.