Toxicity of three pesticides commonly used in Brazil to Pontoscolex corethrurus (Muller, 1857) and Eisenia andrei (Bouche, 1972)

The indiscriminate and excessive use of pesticides poses serious risks to humans and the environment, including soil biota. Ecotoxicological tests are useful to indicate the extent to which these chemicals are harmful and how and where their effects occur. Some of these tests were standardized by ISO (International Organization for Standartization) using the earthworm species Eisenia fetida and Eisenia andrei, both native to temperate climates. However, these species may be of lower relevance for soil ecotoxicological studies since they live in the litter and feed on fresh organic matter. The species Pontoscolex corethrurus, native to tropical regions, may be an alternative for more relevant ecotoxicological tests as it is an endogeic geophagous species. However, little is known of its sensitivity to pesticides. Therefore, avoidance and mortality tests were performed using E. andrei and P. corethrurus and three pesticides commonly used in Brazilian agriculture: carbendazim, carbofuran and glyphosate. The tests were conducted in tropical artificial soil (TAS). For carbendazim, the median avoidance concentration (AC(50)) was 76.1 and 65.8 mg a.i. kg(-1) and the median lethal concentration (LC50) 19.7 and 15.3 mg a.i. kg(-1) for E. andrei and P. corethrurus, respectively. For carbofuran, the AC(50) was 9.7 and 7.3 mg a.i. kg(-1) and LC50 13.5 and 9.3 mg a.i. kg(-1) for E. andrei and P. corethrurus, respectively. Concentrations applied in the field of these two pesticides have toxic effects on both species. Glyphosate showed no toxic effects for either species even at the highest concentration tested (47 mg a.i. kg(-1)), although they displayed avoidance behavior at this concentration. The sensitivity of P. corethrurus appears to be similar to the standard species for the pesticides 'evaluated reinforcing the notion that E. andrei is a good test species. Nevertheless, further studies should be undertaken using other contaminants to confirm the similar sensitivity of both species and the relevance of E. andrei in ecotoxicological tests. (C) 2012 Elsevier B.V. All rights reserved.