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United States Department of Agriculture

Agricultural Research Service

Research Project: BEE DIVERSITY AND THE DEVELOPMENT OF HEALTHY, SUSTAINABLE BEE POLLINATION SYSTEMS

Location: Pollinating Insects-- Biology, Management and Systematics Research

Title: Variation in alfalfa leafcutting bee, Megachile rotundata, reproductive success according to location of nests in U.S. commercial domiciles

Author
item Pitts Singer, Theresa

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 10, 2013
Publication Date: April 1, 2013
Citation: Pitts Singer, T. 2013. Variation in alfalfa leafcutting bee, Megachile rotundata, reproductive success according to location of nests in U.S. commercial domiciles. Journal of Economic Entomology. 106(2): 525-1074.

Interpretive Summary: The alfalfa leafcutting bee is used extensively to pollinate alfalfa for seed production in western North America. However, it usually is not possible to keep bee populations healthy and in good supply in the United States. Variable small-scale environmental conditions are experienced by developing alfalfa leafcutting bees during the nesting season, such as in field domiciles and nesting boards within domiciles, and may influence bee yield. In this study, bee cells were produced in a small alfalfa field and collected according to domiciles, the nesting boards, and different portions of boards. Examination of cells showed that the production of live overwintering prepupae, diseased larvae, other dead eggs and larvae, and cells attacked by natural enemies varied between domiciles, boards in certain orientations, and portions of the boards. Specifically, two domiciles had more live prepupae and fewer parasites than the other two domiciles. Northeast-facing board samples were heavier and had less chalkbrood larvae compared to southwest-facing boards. Outer portions of boards had more live prepupae and less chalkbrood larvae than middle and inner portions. These results suggest that changes in domiciles or changing the orientation of boards within domiciles might improve overall bee yield. Also, to accurately assess the quality of bee populations managed in the commercial loose cell system, a sample of bees should be taken from a pooled sample from all boards in each domicile. Each domicile sample should then be evaluated according to what proportion that domicile contributed to the yield of the whole field (e.g., by weight or volume).

Technical Abstract: The alfalfa leafcutting bee, Megachile rotundata F., is used extensively to pollinate alfalfa for seed production in western North America. However, it usually is not possible to sustain bee populations in the United States. Variable microenvironments are experienced by developing alfalfa leafcutting bees during the nesting season, such as in field domiciles and nesting boards within domiciles, which may influence bee reproductive success. In this study, bee cells were produced in a small alfalfa field and collected according to domiciles, the nesting boards, and different portions of boards. Examination of cells showed that the production of live overwintering prepupae, diseased larvae, other dead eggs and larvae, and cells attacked by natural enemies varied between domiciles, boards in certain orientations, and portions of the boards. Specifically, two domiciles had more live prepupae and fewer parasites than two other domiciles. Northeast-facing board samples were heavier and had less chalkbrood larvae compared to southwest-facing boards. Outer portions of boards had more live prepupae and less chalkbrood larvae than middle and inner portions. These results suggest that reproductive success could be altered by structural changes in domiciles or changing the orientation of boards within domiciles. Also, to accurately assess the quality of bee populations managed in the commercial loose cell system, a sample of bees should be taken from a pooled sample from all boards in each domicile. Each domicile sample should then be evaluated according to its proportional contribution to the whole field’s progeny production (e.g., by weight or volume).

Last Modified: 8/1/2014
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