A greenhouse study was designed to evaluate a series of silicone adjuvants for increasing efficacy and rainfastness of Na-acifluorfen, isopropylamine-glyphosate, and Na-bentazon on velvetleaf and common lambsquarters. Silicone adjuvants were identified that increased both herbicide efficacy and rainfastness at 0.9 to 1.2 L ha-1. Specificity of adjuvants for specific target weed species and herbicides was evident. Effective silicone adjuvants were identified that did not increase soybean injury by Na-acifluorfen or Na-bentazon beyond that observed with crop oil concentrate. The efficacy of the best silicone adjuvant did not appear to be solely a function of reduced surface tension of the spray solution.
