Combined effect of two agrochemicals on Aporrectodea caliginosa in a semi-arid land

Abstract

Glyphosate and deltamethrin are used worldwide to control pests in agriculture. However, information about their toxic effects on soil fauna is still insufficient. Therefore, we focused on the individual and combined effects of these pesticides, in artificial soil tests on the earthworm species Aporrectodea caliginosa. Endpoints were behavior, mortality, growth inhibition and morphology. The insecticide had a significant effect on the behavior. The percentage of migrant earthworms to the control soils increased with the increase of concentrations reaching 75%. At the opposite, 76.19℅ of earthworms preferred glyphon-treated soils. The insecticide showed toxicity with dose-response relationship, which leaded to values of LC50-14days = 2215.71µg/kg and LC90-14days = 51869.24µg/kg. However, Glyphon caused negligible mortality of A.caliginosa. The growth rate was inhibited by the insecticide much more than the herbicide. However, the mixture had a repulsive effect, an antagonistic interaction on the mortality and no effect on the growth rate of A.caliginosa. The insecticide altered morphology of exposed earthworms to different concentrations. Symptoms of this alteration ranged from color change of the tegument to lysis of the body wall. While, A.caliginosa treated with Glyphon and mixture showed intact bodies. Our data show that Glyphosate and Deltamethrin could be used safely if recommended doses are respected.