A two years field experiment to assess the impact of two fungicides on earthworm communities and their recovery

Abstract

Recent EFSA (European Food Safety Authority) reports highlighted that the ecological risk assessment of pesticides needed to go further by taking more into account the impacts of chemicals on biodiversity under field conditions. We assessed the effects of two commercial formulations of fungicides separately and in mixture, i.e., Cuprafor Micro® (containing 500 g kg -1 copper oxychloride) at 4 (C1, corresponding to 3.1 mg kg -1 dry soil of copper) and 40 kg ha -1 (C10), and Swing® Gold (50 g L -1 epoxiconazole EPX and 133 g L -1 dimoxystrobin DMX) at one (D1, 5.81 10 -2 and 1.55 10 -1 mg kg -1 dry soil of EPX and DMX, respectively) and ten times (D10) the recommended field rate, on earthworms at 1, 6, 12, 18 and 24 months after the application following the international ISO standard no. 11268-3 to determine the effects on earthworms in field situations. The D10 treatment significantly reduced the species diversity (Shannon diversity index, 54% of the control), anecic abundance (29% of the control), and total biomass (49% of the control) over the first 18 months of experiment. The Shannon diversity index also decreased in the mixture treatment (both fungicides at the recommended dose) at 1 and 6 months after the first application (68% of the control at both sampling dates), and in C10 (78% of the control) at 18 months compared with the control. Lumbricus terrestris, Aporrectodea caliginosa, Aporrectodea giardi, Aporrectodea longa, and Allolobophora chlorotica were (in decreasing order) the most sensitive species to the tested fungicides. This study not only addressed field ecotoxicological effects of fungicides at the community level and ecological recovery, but it also pinpointed some methodological weaknesses (e.g., regarding fungicide concentrations in soil and statistics) of the guideline to determine the effects on earthworms in field situations.

Toward a harmonized methodology to analyze field side effects of two pesticide products on earthworms at the EU level

“…The recommended doses correspond to 199.5 and 75 g ha −1 DMX and EPX, respectively. The mixture (called M) was composed of Cuprafor Micro (0.75 kg Cu ha −1 in April, 0.7 kg Cu ha −1 in May, 1.25 kg Cu ha −1 in June, and 1.25 kg Cu ha −1 in September 2016) and Swing Gold at the recommended dose (1.5 L ha −1 ). The results are not presented here (see Amossé et al, 2020 for details).…”

“…However, the impact of pesticide applications on the annelid community and population structure in the field is less documented. Recently, we carried out a two‐year field experiment to assess the impact of two fungicides on earthworm communities and their recovery (Amossé et al, 2020 ). In this study, we highlighted the negative effects of dimoxystrobin (DMX) and epoxiconazole (EPX)‐based and copper‐based products on earthworm abundance and biomass (mainly on one ecological category of earthworms, i.e., anecics) 12 months after the first application.…”

“…The aim of the present study was to use a field study (Amossé et al, 2020 ) based on the ISO guideline 11268‐3 ( 2014 ) and the de Jong guidance (de Jong et al, 2006 ) to propose potential improvements to the ISO guideline. Furthermore, recommendations made from the present study could help in the development and/or revision of guidelines for earthworm field studies.…”

“…In Amossé et al ( 2020 ), the tested substances were chosen for their potential negative effects on earthworm populations and because they were used in different farming systems, either organic or conventional farming. At the field level, the results published in our recent studies (Amossé et al, 2020 ) revealed significant effects on earthworm biomass and abundance in plots treated with the highest tested rate (i.e., 10 times the authorized application rates mentioned on the label of the product in France) of Swing Gold one month after the application. The soil dissipation of DMX and EPX and their bioavailability to earthworms were studied at the same time (Nélieu et al, 2020 ).…”

“…FIGURE 2 Mean residues of copper (total contents, n = 4 plots, and standard deviation) in sampled soils, in mg kg −1 . Modified fromAmossé et al (2020) …”