Effects of procymidone, fludioxonil and pyrimethanil on two non-target aquatic plants

Procymidone, fludioxonil, and pyrimethanil are widely used to control the p athogenic fungus Botrytis cinerea in Champagne's vineyards. These fungicide s may end up in surface waters and present potential risks for aquatic vasc ular plants and algae. Therefore, their toxicity was evaluated on Lemna min or and Scenedesmus acutus in six-day or 48-h tests, respectively. Based on growth and chlorophyll (Chl) content of L. minor and S. acutus cultures, th e results showed that the alga was the most sensitive to the fungicides. Am ong the fungicides, pyrimethanil was the most toxic for L. minor, its nomin al IC50 was 46.16 mg l(-1) and that of the other two was > 100 mg l(-1). In contrast, pyrimethanil appeared the least toxic for S. acutus at low conce ntration, nominal IC50 were 22.81, 4.85, and 4.55 mg l(-1) for pyrimethanil , fludioxonil, and procymidone, respectively. Fate of the fungicides in the media was also investigated and acute toxicity of the agrochemicals is dis cussed in regard to concentration in the culture media. Poor solubility of procymidone and fludioxonil appeared to be partly responsible for the low t oxicity of these fungicides. Based on these toxicity data and the concentra tions found in ponds collecting vineyard runoff water, these pesticides sho uld not impair the establishment of pioneer plants. (C) 2001 Elsevier Scien ce Ltd. All rights reserved.