Interactions between floral resources and bees (Hymenoptera: Megachilidae) in commercial alfalfa seed fields
1999
Strickler, K. | Freitas, S.
We monitored flower resources around 9 Megachile rotundata (F.) bee shelters in 7 commercial seed fields of alfalfa, Medicago sativa L. (Leguminosae) seed fields to understand better the interactions between floral resources and bee pollinators. A composite pattern of floral resource availability demonstrated an initial burst of bloom, followed by a linear decline in total flowers per raceme and an exponential decline in numbers of racemes with open flowers over the season. Open flowers per raceme declined exponentially at a more rapid rate than did total flowers per raceme, and standing crop of nectar sugar declined even more rapidly. Thus, floral resources available to bees declined to low level within 3-4 wk of bee introduction. Pollinator activity was relatively constant within a week or 2 of release of bees into the fields. Numbers of open flowers and nectar availability declined more rapidly close to bee shelters than at a distance from them. We interpret the rapid decline in floral resources partly as a result of steady pollination over time. The decline in floral resources may contribute to poor bee yields in alfalfa seed fields.
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