Interactions of Several Paraquat-Surfactant Mixtures

Publisher Website
Google Scholar
Abstract
Measurements were made of plant toxicity and of several physical and chemical properties of spray solutions containing l,l[image]-dimethyl-4, 4[image]-bipyridinium salt (paraquat) and either anionic, nonionic, or cationic surfactants. Surface tension and pH values were variable among 10 surfactant-paraquat mixtures and also at 0.1 and 1.0% surfactant concentrations, but neither showed any correlation with herbicidal activity on corn when all surfactants were considered. All 4 nonionic, both cationic, and 2 out of 4 anionic surfactants markedly enhanced paraquat toxicity at appropriate concentrations. Studies of UV absorbance of herbicide and surfactant solutions, alone and in combination, and adsorption of paraquat-C14 at solution-air interfaces indicate that significant interactions occurred between paraquat and the anionic surfactants. Foliar toxicity studies offered substantiating evidence of such interactions; however, the degree or lack of enhancement of paraquat toxicity was strongly influenced by plant species (corn vs. bean) and the type and concentration of surfactant. No surfactant-paraquat combinations studied were less effective than 1/8 oz/A of paraquat used alone.