Avoidance and reproduction tests with the predatory mite Hypoaspis aculeifer: effects of different chemical substances.

Few toxicity data exist in the literature on the toxicity of chemicals to the predatory mite Hypoaspis aculeifer, but no information is available on its avoidance response. To assess the relevance of the avoidance behavior of H. aculeifer and the relative sensitivity of the mite in comparison with other invertebrates, avoidance and reproduction tests were conducted with 7 chemicals using standardized guidelines. The chemicals (deltamethrin, chloropyrifos, dimethoate, Cu, NaCl, phenanthrene, and boric acid) were selected so as to cover varying chemical classes. For all 3 pesticides tested, avoidance response showed lower sensitivity than reproduction and survival (avoidance median effective concentration [EC50] > reproduction EC50/median lethal concentration [LC50] values). However, for Cu, NaCl, and phenanthrene, the avoidance response showed similar sensitivity as reproduction (avoidance EC50 ≤ reproduction EC50 values), whereas for boric acid, similar sensitivity as survival (avoidance EC50 ≤ LC50 values). Although the mite H. aculeifer appears less sensitive to some of the chemicals tested than most other soil invertebrates, its status as the only predator among organisms for which standardized tests are available affirms its inclusion in routine ecotoxicity assessment. The results of the avoidance test with H. aculeifer suggest its potential usefulness as a rapid screening test for risk assessment purposes.