Short-term effects of two fungicides on enchytraeid and earthworm communities under field conditions

Because of the wide use of pesticides in agriculture, there is still a need of higher-tier field studies to assess ecotoxicological effects of commercial formulations on a wider variety of non-target soil organisms such as soil annelids. We here tested the effects of different concentrations of two fungicide formulations, i.e., Cuprafor Micro^® (composed of 500 g kg^-1 copper oxychloride) and Swing Gold^® (composed of 50 g l^-1 epoxiconazole and 133 g l^-1 dimoxystrobin) on two families of terrestrial oligochaetes (Lumbricidae and Enchytraeidae) after 1 month of exposure. We also assessed the feeding activity of soil organisms using the bait lamina method. Along with the feeding activity, the enchytraeid density, diversity and communities were not different in the control and the contaminated plots. By contrast, epigeic earthworms were absent and earthworm diversity and densities of anecic species decreased significantly in the plots contaminated at ten times the recommended dose of the Swing Gold^® formulation. The copper fungicide (at 0.75 and 7.5 kg Cu ha^-1) and the treatment with the pesticide mixture (Cuprafor Micro^® at 0.75 kg Cu ha^-1 and Swing Gold^® at the recommended dose) did not affect Oligochaeta communities compared with the control, except the Shannon index for earthworms in the mixture of both fungicides. Responses of the two annelid families to the tested pesticides were different with higher effects observed on the diversity and the community structure of earthworms compared with enchytraeids. This study allowed detecting early changes on oligochaete populations after pesticide application.