Oilseed Rape, Bees and Integrated Pest Management

Abstract

As a major mass-flowering crop producing an abundance of nectar and pollen, oilseed rape is very attractive to honey bees, bumblebees and solitary bees. It provides a food resource of considerable value in sustaining bee populations in agroecosystems at a time when bees are in decline. Although the flowers are self-fertile, they are entomophilous, and pollination studies, both in the glasshouse and in the field, suggest that bee foraging activities on the crop have many beneficial effects for the grower, including improving both the quantity and quality of the seed produced. However, bees foraging on the crop are vulnerable to the effects of insecticides, mostly pyrethroids applied to the crop, particularly when these are applied during flowering to control inflorescence pests. Effects may be lethal or sub-lethal; the latter have been little studied but there is growing evidence that insecticides affect many aspects of bee behaviour and physiology, such as division of labour, foraging and orientation, reproduction and respiration. Husbandry practices on the crop must therefore seek to minimise the use of insecticides on the crop, particularly during flowering, in order to sustain and not diminish bee populations foraging on the crop. Bees may even have a role in integrated pest management strategies incorporating biocontrol through their capacity to vector entomopathogenic fungal spores to the flowering canopy of oilseed rape to kill inflorescence pests.