High levels of copper and persistent synthetic pesticides in vineyard soils

Abstract

Downy mildew (Plasmopara viticola), powdery mildew (Erysiphe necator) and bunch rot (Botrytis cinerea) are the most prevalent fungal diseases in viticulture. To protect grapevines from these diseases both synthetic chemical and organic plant protection products (PPPs) are applied, with treatment frequencies ranging from 7 to 20 times per season depending on plant protection strategy (conventional or organic). This widespread use of PPPs raises concerns about their impact on soil health. Until now a systematic and detailed assessment of pesticides and copper residues in vineyard soils is missing. In this study, we analyzed soil samples from 62 Swiss vineyards for 146 synthetic pesticides and copper. Up to 60 pesticides were detected per vineyard and almost 13 times higher sum concentrations were found under conventional compared to organic management. Additionally, long-term (>20 years) organically managed vineyards, where no synthetic pesticides are used, were found to have up to 32 different synthetic pesticides. Consequently, various pesticides had a much higher persistence in soil than expected based on reported degradation rates, indicating that risk assessment procedures by governmental agencies need further consideration. Contrary to popular belief, soil copper content was found to be comparable across both organic and conventional management strategies. A literature-based risk assessment revealed that the pesticide and copper concentrations in vineyard soils frequently reached levels considered potentially harmful to soil organisms. Initial analyses on the effects on the soil microbial community are underway. Our study demonstrates that pesticide and copper contamination in viticultural soils is high compared to other land uses. According to the risk assessment, this poses a potential threat to soil organisms that should be targeted in research and policy making.