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United States Department of Agriculture

Agricultural Research Service

Title: Alfalfa Leafcutting Bee Population Dynamics, Flower Availability, and Pollination Rates in Two Oregon Alfalfa Fields

Authors
item Bosch, Jordi - USU-BIO.DPT.,LOGAN,UT
item Kemp, William

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 15, 2004
Publication Date: August 1, 2005
Citation: Bosch, J., Kemp, W.P. 2005. Alfalfa leafcutting bee population dynamics, flower availability, and pollination rates in two Oregon alfalfa fields. Journal of Economic Entomology. 98(4):1077-1086.

Interpretive Summary: Since the 1970's it has become ever harder for U.S. alfalfa seed producers to increase alfalfa leafcutting bee populations used for alfalfa pollination. In 1998, we monitored alfalfa leafcutting bee population dynamics and foraging behavior, as well as alfalfa bloom, pollination rates and seed yields in two fields in eastern Oregon. Despite marked differences in bee management, establishment was very similar in the two fields (~0.5 females per nesting cavity), and lagged peak bloom by 2 weeks. Pollination rates increased from 0-10% in the first two weeks to 80-90% in weeks 4-5. By then, it was difficult for alfalfa leafcutting bee females to find untripped (non-pollinated) flowers. Alfalfa leafcutting bee progeny mortality was 54-78%. Seed yields were very high (~2200 kg/ha) in both fields. We contend that similar seed yields, and improved bee production, could be accomplished with smaller bee populations, better timed with alfalfa bloom.

Technical Abstract: Since the 1970's it has become ever harder for U.S. alfalfa seed producers to increase Megachile rotundata populations used for alfalfa pollination. In 1998, we monitored M. rotundata population dynamics and foraging behavior, as well as alfalfa bloom, pollination rates and seed yields in two fields in eastern Oregon. Despite marked differences in bee management, establishment was very similar in the two fields (~0.5 females per nesting cavity), and lagged peak bloom by 2 weeks. Pollination rates increased from 0-10% in the first two weeks to 80-90% in weeks 4-5. By then, it was difficult for M. rotundata females to find untripped (non-pollinated) flowers. Megachile rotundata progeny mortality was 54-78%. Seed yields were very high (~2200 kg/ha) in both fields. We contend that similar seed yields, and improved bee production, could be accomplished with smaller bee populations, better timed with alfalfa bloom.

Last Modified: 9/2/2014
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