Temperature influences the toxicity of deltamethrin, chlorpyrifos and dimethoate to the predatory mite Hypoaspis aculeifer (Acari) and the springtail Folsomia candida (Collembola).

In order to assess the influence of temperature on pesticide toxicity to soil fauna, specimens of the predatory mite Hypoaspis aculeifer and the springtail Folsomia candida were exposed in artificial soil spiked with different concentrations of three pesticides (dimethoate, chlorpyrifos and deltamethrin) at 20°C vs 28°C for the mites and 20°C vs 26°C for the springtails. All tests were carried out according to OECD guidelines. In the mite tests, the toxic effects of dimethoate and chlorpyrifos on survival was about two orders of magnitude more at 28°C than at 20°C. Mite reproduction decreased in the tests with chlorpyrifos and deltamethrin by about four to five orders of magnitude at 28°C than at 20°C. (EC5028°C =1.42 and 2.52mg/kg vs EC5020°C=6.18 and 10.09mg/kg) In the collembolan tests, the toxicity of dimethoate on survival was higher at 26°C than at 20°C (LC5026°C =0.17mg/kg vs LC5020°C =0.36mg/kg), while the opposite was detected for deltamethrin (LC5026°C =11.27mg/kg vs LC5020°C =6.84mg/kg). No difference was found in the test with chlorpyrifos. Effects of dimethoate and chlorpyrifos on reproduction were higher at 26°C than at 20°C (EC5026°C =0.11 and 0.018mg/kg vs EC5020°C =0.29 and 0.031mg/kg respectively), but in the case of deltamethrin the opposite was observed (EC5026°C =12.85mg/kg vs EC5020°C =2.77mg/kg). A preliminary risk assessment of the three pesticides at the two temperature regimes based on the Toxicity Exposure Ratio (TER) approach of the European Union, shows that in general there are few different outcomes when comparing data gained at different temperatures. However, in the light of the few comparisons made data gained in temperate regions should be used with caution in the tropics.