Assessing the exposure and toxicity of pesticides to bumblebees (Bombus sp.)

Abstract

Many of the reported pesticide incidents involving honeybees probably also result in mortality of bumblebees and, together with a reduction in suitable habitat, these have resulted in the decline in bumblebees in the UK over the last 20 years. Applications of sprays, e.g. pyrethroids, to flowering crops or weeds at times when honeybees are less active are likely to result in unreported bumblebee deaths. There is a need to protect foraging bumblebees from direct overspray during the early morning and late evening when pesticides which are repellent but highly toxic are applied, i.e. pyrethroids. Of particular concern are those pesticides applied when queens are emerging and establishing colonies, e.g. March/April, when colonies may be significantly impacted by the loss of a small number of workers or the queen. This is a problem which cannot readily be addressed by risk management measures due to differing foraging profiles of honeybees and bumblebees but does need to be taken into account in risk assessment and the development of more selective compounds.