Abstract

Earthworms might be limited in their activities on soil by pesticides used at important rates in agriculture and human pathogenic micro-organisms introduced in soil by excreta. This study using a modified toxicity filter paper contact test from Organisation for Economic Co-operation and Development (OECD), aimed at assessing the toxicity of six pesticides formulations and six micro-organisms on the earthworm Eisenia fetida. The study performed over 7 months at the laboratory QAlEA (University of Caen Normandie, France), analysed the mortality every 24 h for 96 h and at 96 h of E. fetida when exposing to pesticides and microbial suspensions. The statistical test used is the Student’s t-test at the significant level of 0.05. No mortality of earthworms was observed when testing these pesticides at their recommended agricultural concentrations. Toxicity order from the highest to the lowest, based on LC₅₀, was Capiscol, Stratos Ultra Jardin, Polyvalent, Roundup GT Plus, Polyflor and KB Limace. Among tested micro-organisms, only Enterobacter cloacae (culture broth) and Listeria monocytogenes (culture broth and supernatant) generate mortalities of E. fetida. Finally, all these tested pesticides do not lead to E. fetida mortality if they are used at their recommended agricultural concentrations. Earthworms species E. fetida are also stressed by some micro-organisms. Furthermore, the filter paper contact test OECD might be used as a tool to evaluate the response of E. fetida to abiotic and biotic stresses.

Key words: Stress, toxicity, pesticides, micro-organisms.