EFFECT OF NONIONIC NONYLPHENOL SURFACTANTS ON SURFACE PHYSICOCHEMICALPROPERTIES, UPTAKE AND DISTRIBUTION OF ASULAM AND DIFLUFENICAN

The effect of non-ionic nonylphenol (NP) surfactants containing 4-14 e thylene oxide (EO) molecules on the distribution of asulam and diflufe nican was investigated in Pteridium aguilinum L. Kuhn and Avena fatua L. The distribution of the herbicides was dependent on the EO content and concentration of surfactant and differed between plant species and herbicide. The surface properties of contact angle, droplet diameter and surface tension were examined. For solutions of asulam, the greate st reductions in contact angle, surface tension and greatest droplet d iameter were obtained with surfactants of EO 6.5-10 (at 0.001-0.1%). F or solutions of diflufenican, these responses were greatest when appli ed with surfactant of EO 4. Surfactants of EO 6.5-10 increased the upt ake and translocation of [C-14]asulam in P. aquilinum, particularly at surfactant concentrations of 0.01% and 0.1%. All surfactants increase d uptake of [C-14]asulam in A. fatua with no significant effects of su rfactant EO number or concentration. For both species, these was a pos itive correlation between the optimum surface characteristics of the h erbicide droplets and the uptake of asulam. With diflufenican, greates t uptake and translocation by mature frond tissue of P. acquilinum occ urred at the highest concentration of surfactant EO 4; in A. fatua, ho wever, uptake and translocation were not significantly affected by any of the surfactants.