Abstract: Activator adjuvants for herbicides increase herbicide activity and encompass a wide variety of surfactant chemistry. Activator adjuvants may be included in the product formulation by the manufacturer or tank-mixed by the herbicide applicator. Activator adjuvant efficacy is a function of not only the adjuvant but also the herbicide, the particular weed species, and environmental conditions. Proposed modes of activator action include reduction of spray solution surface tension to enhance contact area, solibilization of the leaf cuticle, emulsifier action, increased spray retention, protection of the herbicide in the spray solution, promotion of rainfastness, acting as a cosolvent or copenetrant, modification of spray deposition on plant foliage, and enhanced movement on the foliage surface to areas of greater absorption.

Additional index word: Surfactant.

Abbreviations: AMS, diammonium sulfate; IPA, isopropylamine.