Joint toxicity of three plant protection products to Triticum aestivum (L.) and Brassica rapa (L.)

Abstract

Few studies have been conducted to evaluate the effects of mixtures of chemicals in terrestrial environment. Thus, it seems important to evaluate if the combined application of pesticides currently used in agricultural fields may pose a risk to terrestrial plants. The effects of binary combinations of glyphosate, dimethoate, and spirodiclofen, applied to LUFA 2.2 soil, on the growth (determined following ISO guidelines) of the two species of plants (Brassica rapa and Triticum aestivum) were evaluated by the two reference models for mixture toxicity: concentration addition and independent action. Results of single exposure to the three pesticides indicated a decrease in shoot length and fresh weight of the two plant species only at the highest concentrations tested (approximately 54 times the recommended dose of glyphosate, 37 times the recommended dose of dimethoate, and 22 times the recommended dose of spirodiclofen). Synergism was only found in the combination of glyphosate and dimethoate when the independent action model was fitted to the shoot length and fresh weight of T. aestivum. The results obtained in the present work seem to corroborate that these pesticides have no detrimental effects when applied at recommended doses. The joint toxicity effect of the pesticides was mainly antagonistic.