Effectiveness of the alfalfa leafcutter bee Megachile rotundata Fab. to pollinate four perennial legumes

Abstract

The effectiveness of the alfalfa leafcutter bee, Megachile rotundata Fab., as a pollinator of sainfoin, Onobrychis viciifolia Scop., cicer milkvetch, Astragalus cicer L., birdsfoot trefoil, Lotus corniculatus L., and crown vetch, Securigera varia (L.), and its ability to reproduce on these crops were evaluated. Three treatments were used in the evaluation: plants caged to exclude all pollinators, plants caged with leafcutter bees, and plants exposed to all resident pollinators. These legumes were self-sterile and produced little to no seed when bees were excluded. Percent seed set and yield were higher or at least equal for plants exposed to resident pollinators compared to plants caged with leafcutter bees in all years and plant species. Percent seed set and seed yields in cicer milkvetch were low for caged leafcutter bees confirming previous research. Percent seed set and seed yield for crown vetch were relatively high after the first production year for both open pollinated and caged treatments in spite of this crop being pollinator unattractive. The propagation rates and quality of alfalfa leafcutter bees produced on sainfoin, cicer milkvetch and birdsfoot trefoil was comparable to that produced on alfalfa. The alfalfa leafcutter bee can be recommended as an effective pollinator for these crops, thus increasing options available to seed growers.