Enhancement of Herbicides by Silicone Surfactants

Abstract

In comparative evaluation of adjuvant effects in eight species, nonionic silicone-glycol surfactants enhanced the activity of six herbicides to a greater extent than a standard organic surfactant, whereas cationic amino silicone surfactants enhanced to a lesser extent. The efficacy of the nonionic silicones was associated with (a) a greater enhancing action in species, particularly grasses, that were relatively resistant to herbicides applied without adjuvants and (b) a greater ability to enhance herbicides with very low water solubility. The cationic silicones in combination with some of the herbicides provided less enhancement in moderately sensitive crops than did the standard organic surfactant but provided equivalent enhancement on some weeds. The threshhold concentration for enhancement by silicone-glycols was 0.01% in a susceptible species and 0.1% in a resistant species. In yellow nutsedge ( Cyperus esculentus L.), a silicone-glycol surfactant at a concentration of 0.5% provided greater enhancement of several herbicides than any of three organic surfactants or an emulsifiable oil.