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The alfalfa leafcutter bee, Megachile rotundata: a potential pollinator for some annual forage clovers

Written by
Journal of Apicultural Research
Vol 34 (3) pp. 115-121
September 1995
Article Title

The alfalfa leafcutter bee, Megachile rotundata: a potential pollinator for some annual forage clovers


K W Richards

The effectiveness of the alfalfa leafcutter bee (Megachile rotundata) as a pollinator of arrowleaf clover (Trifolium vesiculosum), berseem or Egyptian clover (Trifolium alexandrinum), crimson clover (Trifolium incarnatum) and Persian clover (Trifolium resupinatum) was evaluated over a 3-year period at Lethbridge, Canada. Treatments consisted of plants caged to exclude all pollinators, plants caged (cages were 40 x 20 x 2 m) with a shelter containing 30 000 leafcutter bees, and plants exposed to all pollinators present, including honey bees, bumble bees and leafcutter bees. The arrowleaf, berseem and crimson clovers were essentially self-sterile and produced very little seed when bees were excluded, whereas about one-third of the Persian clover flowers were self-pollinated. Only for crimson clover was there a significant difference in the percentage seed set between plants caged with leafcutter bees (50.5 ± 2.5%) and those exposed to resident pollinators (70.4 ± 1.1 %). However, the seed yield of plants caged with leafcutter bees was significantly lower than for open-pollinated plants for all clover species except berseem. The lower seed yields from caged plants may have been due to a cage effect reducing leafcutter bee foraging activity. The results, however, show that M. rotundata is an effective pollinator of these annual clovers, thus increasing the options available to seed growers and beekeepers regarding choice of pollinator. The seed production of these annual clovers indicates that they have potential as new legume crops for western Canada.

alfalfa leafcutter bees, Megachile rotundata, pollination, arrowleaf clover, Trifolium vesiculosum, berseem clover, Trifolium alexandrinum, crimson clover, Trifolium incarnatum, Persian clover, Trifolium resupinatum, seed set, seed production, Canada

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