Ecotoxicity testing of pesticides at the soil surface using a non-target terrestrial gastropod.

International audienceFate and effects of pesticides in agrosystem were studied using a non target species living at the interface soil-plant-air, the landsnail Helix aspersa. Fate in and effects on snails of 8 commercial herbicide and fungicide formulations (Roundup® and Bypass® = glyphosate; Basta® = glufosinate; Valiant® Flash = folpet + cymoxanil + fosetyl-Al; Corail® = tebuconazole; Cabrio® Top = pyraclostrobin + metiram-Zn; Thiovit® = sulphur; Bordeaux mixture = copper salts) commonly employed in vineyards were studied in the field and for some of them, in laboratory experiments. Here we present a synthesis of a four-years program that aims to develop various biological methods for in situ biomonitoring and life cycle exposure under controlled conditions. A field study in real conditions of pesticide application revealed few effects on the survival and growth of juvenile snails exposed in microcosms to each different treatment. Glyphosate (4 mg kg-1) and AMPA (8 mg kg-1) were detected in snail tissues. The transfer of pyraclostrobin and tebuconazole was also demonstrated. Internal concentrations were low but however higher than LMR drawn for animal products. The effects of two herbicides, Bypass® and Basta® were studied on the whole life cycle of snails in laboratory conditions. No toxicity was found on survival and growth although an accumulation of glyphosate was revealed in snails (6 mg kg-1) exposed continuously to contaminated food (30 mg kg-1). Bioassays for embryotoxicity testing of chemicals in solution or in the soil showed that all pesticides inhibited egg hatching success at lower concentrations than those applied in the field and the influence of soil characteristics on the toxicity of the pesticides was demonstrated. As bioassays using eggs are considered as in vitro methods, efforts should be given to improve and promote the use of such method. This work led to the proposal of complementary tools available for pesticide risk assessment in terrestrial environment. Analytical difficulties were encountered and it was not possible to finalize the analytical methods for all substances studied. Thus, the determination of pesticide residues in animal tissues still represents an essential challenge for current environmental concerns