Effects of consumer-grade and commercial acetamiprid formulations on the embryonic development of the South African clawed frog Xenopus laevis

The insecticide acetamiprid is a neonicotinoid still approved for outdoor use worldwide. For active use, there are formulations that contain other often unpublished co-formulants in addition to acetamiprid. This study investigated effects of four different acetamiprid formulations (Careo Rosenspray, Careo, Mospilan, Danjiri) in a concentration range of 0.01-100 mg a.i./L on embryonic development of Xenopus laevis. The formulations led to an increase in embryo mortality with LC₅₀-values between 0.5 and 53.2 mg a.i./L depending on the formulation. At sublethal acetamiprid concentrations in Mospilan and Danjiri, the external appearance (body length, oedemas), the early neural development (eyes, heads, brains, cranial nerves) as well as the heart morphology and function were disturbed. Our results show that strict adherence to recommended handling and application conditions of acetamiprid formulations is essential to protect X. laevis. Therefore, pesticide risk assessment and approval renewal procedures must include commercially available combined formulations rather than solely evaluating the active ingredient.