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VIII SIMPOSIO INTERNAZIONALE ICPBR HAZARDS
OF PESTICIDES TO BEES Effetti dell’imidacloprid sulle api Safety of imidacloprid seed dressings to honey bees. A comprehensive overview and compilation of the current state of knowledge Christian Maus (1), Gaëlle Curé (2) and Richard Schmuck (1) (1) Bayer
AG, Bayer Crop Science, Institute for Environmental Biology, Alfred-Nobel-Str.
50, 40789 Monheim, Germany. E-mail: christian.maus.cm@bayer-ag.de In the 1990´s, bee incidents in France were attributed to a seed treatment of sunflowers with imidacloprid. In response to these allegations, numerous studies in various disciplines (ecotoxicology, metabolism, residue analysis) have been carried out to analyse the potential risks arising from imidacloprid seed dressings to honey bees. In parallel, activities were started to elucidate other factors potentially involved in causing the symptoms of the "French Bee Malady". The studies were conducted by several independent research institutes and universities. In addition, Bayer contributed many novel studies covering all fields of relevance. Our presentation will briefly summarize the results demonstrating the safety of imidacloprid containing seed treatments to honeybees and will cover the following aspects: a) a short overview of the history of the allegations of some French beekeepers b) a compilation of the key ecotoxicological studies carried out to investigate the risk posed to honey bees by imidacloprid c) a conclusion on the alleged link between an imidacloprid containing seed dressing and the "French Bee Malady" based on a scientific weight-of-evidence approach. Studies performed include laboratory tests (e.g. acute oral toxicity, proboscis extension reflex test) as well as field and semifield studies (acute and chronic toxicity, brood and colony development, foraging behavior, internal communication, orientation). In laboratory feeding studies, reproducible NOEC values between 10 and 48 m g/kg diet were determined. Trophallaxis-related antifeedant effects were shown at residue levels greater than 10 m g/kg diet. Under field conditions, no adverse effects, including antifeedant responses, were observed for residue levels of 20 m g/kg diet. Imidacloprid residue levels have been analyzed in several relevant matrices (i.e. nectar and pollen from sunflower and rape plants grown from imidacloprid treated seeds). In almost all cases, residue levels found in nectar and pollen from field-grown plants were below the limit of quantification. Relevant metabolites were not detected. Based on these findings, no adverse effects can be anticipated under realistic field exposure conditions. The results of numerous field studies (in sunflowers and rape cultures) carried out under realistic exposure scenarios (under different climatic conditions in several countries) supported this view. No adverse effects could be observed for any of the recorded endpoints. Based on the results and considerations outlined above, it can be concluded with a very high degree of confidence that there is no risk for honey bees posed by imidacloprid seed dressing applications in agricultural practice. Under field conditions and in experiments, a hazard potential was not indicated. The investigations
conducted in parallel make it very likely that the "French Bee
Malady" is caused by a complex of heterogeneous factors -which
nevertheless manifest themselves in similar symptoms- or in a combination
of these factors. These factors involve Varroa infestation, bacterial
diseases, adverse climatic conditions, physiological and/or genetic
incompatibilities, inappropriate bee management practices and poisoning
incidents.
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