Comparative ecotoxicity of chlorantraniliprole to non-target soil invertebrates

The insecticide chlorantraniliprole (CAP) is gaining importance in agricultural practice, but data on its possible negative effects on non-target organisms is severely deficient. This study therefore determined CAP toxicity to non-target soil invertebrates playing a crucial role in ecosystem functioning, including springtails (Folsomia candida), isopods (Porcellio scaber), enchytraeids (Enchytraeus crypticus) and oribatid mites (Oppia nitens). In sublethal toxicity tests in Lufa 2.2 soil, chronic exposure to CAP concentrations up to 1000 mg/kgdw did not affect the survival and reproduction of E. crypticus and O. nitens nor the survival, body weight and consumption of P. scaber. In contrast, the survival and reproduction of F. candida was severely affected, with an EC50 for effects on reproduction of 0.14 mg CAP/kgdw. The toxicity of CAP to the reproduction of F. candida was tested in four different soils following OECD guideline 232, and additionally in an avoidance test according to ISO guideline 17512-2. A significantly lower toxicity in soils rich in organic matter was observed, compared to low organic soils. Observations in the avoidance test with F. candida suggest that CAP acted in a prompt way, by affecting collembolan locomotor abilities thus preventing them from escaping contaminated soil. This study shows that CAP may especially pose a risk to non-target soil arthropods closely related to insects, while other soil invertebrates seem rather insensitive.