SURFACE TENSION-DEPENDENT SURFACTANT TOXICITY ON THE GREEN PEACH APHID, MYZUS-PERSICAE (SULZER) (HEMIPTERA, APHIDIDAE)

Toxicity of 32 surfactants on the green peach aphid, Myzus persicae, were observed at a concentration of 0.1% in order to determine the mechanism of surfactant action. Eight of the surfactants, of various chemical structures, exhibited high toxicities, those eight being two polyoxyethylene alkylethers, one sorbitan fatty acid ester, two octylphenoxypolyethoxyethanols, two dimethyl siloxane derivatives, and one fatty acid salt. Other surfactants with common partial structures to these toxic ones were largely ineffective. And what is more, there were no surfactant-dependent differences in the appearance of the dead aphids-paralyses occurred within hours, the dead aphids attached to leaves by their inserted stylets-suggesting a common physical basis to the toxicity phenomenon irrespective of chemical structure. A close connection between toxicity and surface tension was thereby uncovered, leading to the conclusion that toxicity might be related to aphid suffocation in the highly wettable surfactant solutions.