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

Many of the reported pesticide incidents involving honeybees probably also result in mortality of bumblebees and, together with a reduction in suitabl e 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 c rops or weeds at times when honeybees are less active are likely to result in unreported bumblebee deaths. There is a need to protect foraging bumbleb ees from direct overspray during the early morning and late evening when pe sticides which are repellent but highly toxic are applied, i.e. pyrethroids . Of particular concern are those pesticides applied when queens are emergi ng and establishing colonies, e.g. March/April, when colonies may be signif icantly impacted by the loss of a small number of workers or the queen. Thi s is a problem which cannot readily be addressed by risk management measure s due to differing foraging profiles of honeybees and bumblebees but does n eed to be taken into account in risk assessment and the development of more selective compounds.