Environmental impacts of an imidacloprid-containing formulation: from soils to waters

This experiment utilized laboratory tests with Confidor 20SL (20% imidacloprid) to explore its toxicity to terrestrial and aquatic species. Confidor (imidacloprid) was applied at rates of 0.5, 1, 2, 4, and 8 L/ha (the lowest and highest label application rates are 0.5 and 4 L/ha). Based on these application rates, their tests had 0.13, 0.26, 0.5, 1, and 2 mg/kg imidacloprid in soil. Experiments were carried out with the leachate that resulted from imidacloprid application to clean soil at the rates noted. The aquatic invertebrate test evaluated acute immobilization of Daphina magna after 24 and 48 hours of exposure, as well as chronic effects over 21 days. Concentrations of imidacloprid in the leachate ranged from 13.05 µg/L (from the soil treated with 0.26 mg/kg imidacloprid) to 71.8 µg/L (from soil treated with 2 mg/kg imidacloprid). These leachate values ranged from 25.4% to 50.4% of the imidacloprid initially applied to the soil samples, demonstrating its ability to move from soil into water. While none of the leachates caused acute or chronic mortality to D. magna, the authors note that the quantity of imidacloprid present in the leachate was sufficient to represent threats to other freshwater macroinvertebrates.