The alfalfa leafcutting bee, Megachile rotundata F., has been cultivated by alfalfa seed producers in Western North America for nearly fifty years. In commercial nesting materials, females construct linear nests of about seven "cells", cups constructed of excised leaf pieces provisioned with nectar and pollen, upon which one egg is deposited.
While intense alfalfa leafcutting bee (ALB) management improves alfalfa seed production dramatically, success requires a substantial capital investment in specialized materials and equipment, and in bee storage facilities. To enhance these economic trade-offs for alfalfa seed producers, improvements are needed in our understanding of mortality sources that can limit bee productivity.
In the summers of 2000 and 2001, ALB shelters were placed at three and four sites respectively, at locations in South-central Montana. Throughout July and August, 7,000 nest holes at each site were monitored. Completion dates were recorded for whole nests.
Chalkbrood (Aescosphaera aggregata) occurred at three out of four sites, and parasitoid wasps (Pteromalus venustus) occurred at all four. Parasitism and chalkbrood were highest in first-provisioned cells (those farthest from the nest entrance). Spatial patterns and seasonal trends in ALB mortality displayed important similarities between all sites and both years.
Species 1: Hymenoptera Megachilidae Megachile rotundata (alfalfa leafcutting bee)
Keywords: chalkbrood, Chalcidae
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