Avaliação da influência de diferentes tipos de solos sobre o potencial tóxico do inseticida imidacloprid sobre minhocas e colêmbolos

Abstract

Seed dressing with imidacloprid has been used to control agricultural pests during the early development phase of plants grown in Brazil. However, although this active ingredient (a.i.) controls agricultural pests, imidacloprid can also affect non-target soil, that perform important ecosystem services. Most studies on the impacts of this a.i. for soil quality bioindicators have been performed on artificial soils, which may not represent its effects in Brazilian natural soils, resulting in lower ecological revelance. Because of this, testing to assess the negative effects of imidacloprid on soil fauna in natural soils is essential. The objetive of this study was to assess the toxic effects and ecological risk of imidacloprid for Folsomia candida and Eisenia andrei earthworms in three soil types: Tropical Artificial Soil (TAS), Entisol and Oxisol. For this, chronic toxicity assays were performed with both species, according to the guidelines of the ISO 11268-2: 2012 for earthworms and ISO 11267: 1999 for collembolans. Reductions in reproduction of the tested species were observed in all soils when exposed to the a.i. However, for both species, the highest toxicity was observed in Entisol (EC50 = 0.21 mg kg⁻¹ and 0.09 mg kg⁻ ¹, respectively). In addition, significant exposure risk for these species to this a.i. has been evidenced in all soils tested and, therefore, which warns the need for further investigation. These results indicate that the different soil types can significantly influence the chronic toxicity of imidacloprid, being the highest toxicity observed in Entisol. In addition, we highlighting the need for ecotoxicological assays in natural soils, to achieve more realistic environmental hazard classifications for pesticide formulations used in Brazil.