Abstract

The large-scale use of neonicotinoid insecticides has raised growing concerns about their potential adverse effects on farmland birds, and more generally on biodiversity. Imidacloprid, the first neonicotinoid commercialized, has been identified as posing a risk for seed-eating birds when it is used as seed treatment of some crops since the consumption of a few dressed seeds could cause mortality. But evidence of direct effects in the field is lacking. Here, we reviewed the 103 wildlife mortality incidents reported by the French SAGIR Network from 1995 to 2014, for which toxicological analyses detected imidacloprid residues. One hundred and one incidents totalling at least 734 dead animals were consistent with an agricultural use as seed treatment. Grey partridges (Perdix perdix) and “pigeons” (Columba palumbus, Columbalivia and Columba oenas) were the main species found. More than 70% of incidents occurred during autumn cereal sowings. Furthermore, since there is no biomarker for diagnosing neonicotinoid poisonings, we developed a diagnostic approach to estimate the degree of certainty that these mortalities were due to imidacloprid poisoning. By this way, the probability that mortality was due to poisoning by imidacloprid-treated seeds was ranked as at least “likely” in 70% of incidents. As a result, this work provides clear evidence to risk managers that lethal effects due to the consumption by birds of imidacloprid-treated seeds regularly occur in the field. This in turn raises the question of the effectiveness of the two main factors (seed burying and imidacloprid-treated seeds avoidance) that are supposed to make the risk to birds negligible. Risk factors and the relevance of mitigation measures are discussed.

Highlights

  • The large-scale use of neonicotinoids has raised growing concerns about their potential adverse effects on nontarget invertebrates especially on pollinators

  • We reviewed wildlife incidents reported by the French SAGIR Network from the 1 January 1995 to the 31 December 2014 and for which residue of neonicotinoids were detected

  • Given that we pooled a 20-year data, we investigated the spatiotemporal coincidence between the occurrence of these incidents and the use of imidacloprid as seed treatment in order to assess the strength of this association (Fox 1991; Hewitt et al 2003)

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Summary

Introduction

The large-scale use of neonicotinoids has raised growing concerns about their potential adverse effects on nontarget invertebrates especially on pollinators (see Pisa et al 2014 for a review). In December 2013, the European Union banned the use of three neonicotinoid insecticides (clothianidin, imidacloprid and thiametoxam) for seed coating, soil treatment and foliar treatment on crops attractive to pollinators. Their use after crop flowering, or on crops harvested before flowering, and for seed treatment of winter cereals continues to be approved (Regulation 485/ 2013). Neonicotinoids are insecticides that act as nicotinic acetylcholine receptor (nAChR) agonists. They have a greater affinity for insect nAChRs than to those of vertebrates (Tomizawa and Casida 2005).

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