The Impact of Adjuvants on Herbicide Antagonism

Abstract

Adjuvants are used to improve spray delivery, to increase spray retention on weed foliage, and to enhance foliar penetration by postemergence herbicides for increased herbicide efficacy. Numerous factors govern adjuvant efficacy, including the specific herbicide, plant species, and environmental conditions. Adding superior surfactants as adjuvants to a sethoxydim tank mix with Na-bentazon may overcome the Na-bentazon antagonsim of sethoxydim activity by facilitating increased sethoxydim absorption and by masking the antagonism similar to increasing the sethoxydim rate. Herbicides such as Na-bentazon contribute alkaline or alkaline earth cations that can form salts of a weakly acidic herbicide such as sethoxydim that are not absorbed readily by the plant. Adding abundant ammonium from ammonium sulfate or other sources may prevent and/or may overcome this antagonism.