Abstract
Neonicotinoids are widely used systemic insecticides which, when applied to flowering crops, are translocated to the nectar and pollen where they may impact upon pollinators. Given global concerns over pollinator declines, this potential impact has recently received much attention. Field exposure of pollinators to neonicotinoids depends on the concentrations present in flowering crops and the degree to which pollinators choose to feed upon them. Here we describe a simple experiment using paired yellow pan traps with or without insecticide to assess whether the commonly used neonicotinoid imidacloprid repels or attracts flying insects. Both Diptera and Coleoptera exhibited marked avoidance of traps containing imidacloprid at a field-realistic dose of 1 µg L−1, with Diptera avoiding concentrations as low as 0.01 µg L−1. This is to our knowledge the first evidence for any biological activity at such low concentrations, which are below the limits of laboratory detection using most commonly available techniques. Catch of spiders in pan traps was also slightly reduced by the highest concentrations of imidacloprid used (1 µg L−1), but catch was increased by lower concentrations. It remains to be seen if the repellent effect on insects occurs when neonicotinoids are present in real flowers, but if so then this could have implications for exposure of pollinators to neonicotinoids and for crop pollination.
Highlights
Declines in pollinator abundance have led to fears of a ‘pollination crisis’ which threatens both agricultural productivity and biodiversity [1,2]
The number of Diptera caught was strongly reduced when imidacloprid was present, at all three concentrations, the repellent effect became markedly weaker at lower concentrations (Figure 1a, Table 1)
Coleoptera exhibited a similar response at the highest concentration used (1 mg L21), and there was no discernible effect at lower concentrations (Figure 1b, Table 1)
Summary
Declines in pollinator abundance have led to fears of a ‘pollination crisis’ which threatens both agricultural productivity and biodiversity [1,2]. Most crops are treated with one or more insecticide, leading to a potential conflict between the need to manage insect pests and the risks of harming pollinator populations. One group of insecticides in particular, the neonicotinoids, have been suspected of contributing to declines in bees [6,7,8,9]. These chemicals are among the most widely used pesticides globally, and are routinely used as seed dressings for crops such as oilseed rape and sunflower. In the UK, use of neonicotinoids has increased year on year since 1994, with ,80,000 kg applied to .1.2 million hectares of crops in 2010 [11]
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