ORGANOSILICONE SURFACTANTS AS ADJUVANTS FOR AGROCHEMICALS

The literature has been reviewed and 160 references are presented to p rovide an overview of organosilicones as adjuvants for agrochemicals. Early studies (1973-1981) elucidated the special properties of these c ompounds, notably their extreme spreading and, by virtue of the except ionally low surface tensions of their aqueous solutions, the ability t o induce infiltration of spray formulations into foliage via stomata. Subsequent research at the New Zealand Forest Research Institute explo red these and other properties in-depth, and demonstrated that they en abled the herbicide glyphosate to be used as a cost-effective alternat ive to 2,4,5-T for the control of forest scrubweeds. As a result, in 1 985, 'Silwet' L-77 was the first organosilicone adjuvant to be commerc ialised, and various other products have subsequently been introduced. The chemistry and synthesis of these organosilicones have been detail ed. A mechanistic approach has been adopted to consider the effects of the distinctive properties of organosilicones in each of the processe s involved in spray application of agrochemicals. Commencing with spra y formulation, the topics of foaming, hydrolytic stability and interac tions with co-formulants are discussed. Progressing to spray applicati on, consideration is given to the effects of organosilicones on atomis ation and impaction (wetting, adhesion/reflection, spreading, retentio n/run-off), and the resultant influences on the activity of protectant agrochemicals. An assessment of the use of organosilicones with syste mic agrochemicals includes examination of effects on foliar uptake, vi a both cuticular and stomatal pathways, and the rainfastness which the latter provides. Also considered is the physiological behaviour of or ganosilicones, specifically phytotoxicity and effects on translocation of active ingredients. The current and potential future use of organo silicones with herbicides, foliar nutrients, growth regulators, insect icides and fungicides is discussed, as is the specificity of their eff ects. Additionally, the potential application of organosilicone chemis try to adjuvant classes other than the spreader/penetrant type investi gated to date is considered. Finally, the issues of registration, hand ling hazards, both toxicological and chemical, and environmental impac t are discussed. The literature reviewed demonstrates the sound scienc e base on which this novel class of organosilicone adjuvant chemistry rests.