International audienceAssessment of the toxicity of individual pesticides to honeybees is routinely assessed. However, few data have been generated for realistic mixtures of neonicotinoid insecticides and fungicides particularly with regard to exposure levels used. Assessment of the effects of exposure of bees to predicted residues following sprayed applications of ergosterol biosynthesis inhibitor fungicides on the contact and oral toxicity of a range of neonicotinoid insecticides (thiamethoxam, clothianidin, imidacloprid and thiacloprid) showed only low levels of synergism (<3-fold maximum). Further studies showed that the scale of increase in toxicity was fungicide dose dependent with greater synergy of oral toxicity of thiamethoxam following contact dosing with propiconazole. This underlines the need for the use of realistic exposure levels and routes in studies

Abstract-It has been suggested that reduced behavioral activity of birds exposed to anticholinesterase pesticides could bias measures of exposure in field studies if the worst-affected individuals were underrepresented in samples collected by shooting or netting. To assess the likely scale of such biases, European starlings (Sturnus vulgaris) were housed in large aviaries containing simulated bushes made from natural vegetation. Each bird was given a near-lethal dose of the organophosphorus pesticide chlorfenvinphos, and the proportion of time spent in and out of cover was recorded before and after treatment. Use of cover by exposed birds increased significantly 0 to 7 h after treatment, whereas feeding and flying activity decreased. On the following day, there was little difference in the use of cover by exposed and control birds. Mathematical models were used to estimate the effect of these behavioral changes on the sampling of birds from wild populations. The results confirm the potential for sampling bias to occur after acute pesticide exposure. This bias is reduced in samples taken over 24 h after exposure, but delayed samples are unlikely to be representative of cholinesterase (ChE) inhibition at the time of maximal effect. When poisoned birds seek cover, it is more difficult to find casualties in field trials and the probability that dead birds will be found and recorded in wildlife casualty monitoring schemes is reduced. We conclude that considerable caution is required in using ChE activity as an indicator of exposure in avian field trials.

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