Potential of the alfalfa leafcutter bee, Megachile rotundata (F.) (Hym., Megachilidae) to pollinate hairy and winter vetches ( Vicia spp.)

The effectiveness of the alfalfa leafcutter bee, Megachile rotundata (F.), as a potential pollinator of winter (woollypod) vetch, Vicia dasycarpa Ten., and hairy vetch, Vicia villosa Roth., was evaluated over a 3‐year period. Populations of the most important pollinator of the crop, the honey bee, Apis mellifera L. continue to decrease in North America, thus there is a need to evaluate alternate pollinators so that seed growers can optimize their choice of pollinator. Treatments consisted of plants caged to exclude all pollinators, plants caged with leafcutter bees, and plants exposed to resident pollinators including alfalfa leafcutter bees. These vetches were self‐sterile and produced very little seed when bees were excluded. Pods and seeds per raceme, seeds per pod, percentage seed set and yield were significantly higher for plants of both species exposed to resident pollinators compared to plants caged with leafcutter bees. Significant differences between the two treatments indicate that the alfalfa leafcutter bee would not serve as an effective pollinator for these vetches. However, if insufficient populations of honey bees or resident native bees exist in an area, only then may leafcutter bees have a place in commercial seed production. Several species of bumble bee were the main pollinator of these crops in Alberta, Canada. The seed production of these vetches indicates they may have potential as new legume crops for western Canada.