Abstract ‘Sylgard® 309’ organosilicone surfactant is a very effective adjuvant for broadleaf weed control with a number of herbicides. It is also effective in providing rainfastness lo these post‐emergence herbicide applications. To elucidate the basis for herbicide activity enhancement and rainfastness, the absorption of [ 14 C]acifluorfen, [ 14 C]bentazone and [ 14 C]‘Sylgard 309’ were studied. Non‐ionic surfactants and crop oil concentrates were used as adjuvants with [ 14 C]acifluorfen and [ 14 C]bentazone, respectively, for purposes of comparison. Maximum absorption of [ 14 C]acifluorfen and [ 14 C]bentazone was obtained within 15 min after herbicide application with the organosilicone, versus ≥ 24 h with the convenlional adjuvants. [ 14 C]‐Organosilicone absorption closely paralleled that of the [ 14 C]‐herbicides. The organosilicone appears to exert its action by increasing greatly herbicide absorption. The enhancement effect did not appear to be a function of reduced surface tension. Rainfastness appeared to be a result of greatly accelerated herbicide penetration through the leaf cuticle in the presence of the organosilicone.
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Roggenbuck et al. (1993) studied this question.