Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/15/2009
Publication Date: 7/12/2009
Citation: Pitts Singer, T., James, R.R. 2009. Prewinter Management Affects Megachile rotundata (Hymenoptera: Megachilidae) Prepupal Physiology and Adult Emergence and Survival. Journal of Economic Entomology 102(4):1407-1416. Interpretive Summary: The alfalfa leafcutting bee is widely used as a pollinator for production of alfalfa seed, and populations of these bees can be maintained by alfalfa seed growers or can be purchased from mostly Canadian bee providers. Bees raised in Canada are generally healthier and have higher survival compared to bees raised in the U.S. We investigated whether storage of the bees at the end of the field season at a moderately warm temperature for different lengths of time affects the survival of bees over the winter or during spring/summer incubation. Our results show that getting the bees into winter storage in November or December, and then incubating them in late May, results in longer-lived adult females that require slightly longer to emerge from cocoons compared to bees incubated in late June. In conclusion, some prewinter management protocols for alfalfa leafcutting bee commercial stocks may be more effective than others in achieving optimal adult emergence synchrony, as well as adult survival and longevity for pollination of alfalfa. More studies are needed to determine what conditions are detrimental to bee survival before being placed into winter storage.
Technical Abstract: The alfalfa leafcutting bee, Megachile rotundata F. (Hymenoptera: Megachilidae) is widely used as a pollinator for production of alfalfa seed, and populations of these bees can be maintained by alfalfa seed growers or can be purchased from mostly Canadian bee providers. Megachile rotundata raised in Canada have higher survival rates during incubation after winter storage than bees produced in the northwestern U.S., but no reason has been found for this. We investigated whether storing immature M. rotundata for various time periods at a warm temperature (16ºC) before winter or allowing them to remain unmanaged at ambient temperatures affects physiological aspects of prepupae during the winter as well as the survival and longevity of adult bees after spring or summer incubation. Our results show that the timing of the onset of winter storage and incubation does affect prepupal weights, prepupal lipid and water contents, adult emergence, and adult female longevity. Winter storage of prepupae in November or December with a late June incubation time results in heavier adults that emerge more readily than bees incubated in May. However, adult females incubated in late May thrive longer than June-incubated bees if fed a honey-water diet. Thus, some prewinter management regimes for M. rotundata commercial stocks may be more effective than others in achieving optimal adult emergence synchrony, as well as adult survival and longevity for pollination of a summer crop.