Low temperature stress during pupal development and its effects on adult performance in alfalfa leafcutting bees

Authors: EDWARDS, JERRESIA - North Dakota State University; GREENLEE, KENDRA - North Dakota State University; CUMMINGS, SARA - North Dakota State University; Yocum, George; Rinehart, Joe; Kemp, William - Bill

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 10/2/2013
Publication Date: 2/20/2014
Citation: Edwards, J.D., Greenlee, K.J., Cummings, S.E., Yocum, G.D., Rinehart, J.P., Kemp, W.P. 2014. Low temperature stress during pupal development and its effects on adult performance in alfalfa leafcutting bees [abstract]. Emerging Researchers National Conference. February 20-22, 2014. Washington, D.C. page A111.

Interpretive Summary: Seventy percent of crops grown for human food production are dependent on pollinators. The value of this pollination service worldwide is estimated to be over 100 billion dollars annually. This value does not include agriculture products that are not directly consumed by humans such as alfalfa that is used as an input for meat and milk production. The alfalfa leafcutting bee Megachile rotundata is the primary pollinator used in the production of alfalfa seed in North America. There is growing interest in M. rotundata for pollination of various specialty crops. These bees may, in the course of normal management, need to be exposed to constant low temperatures to slow their development in order to match their peak nesting activity to crop bloom. An alternative method that increases survival is to give the bee a daily short high temperature pulse during the low temperature storage. Since low temperature exposure is known to cause developmental abnormalities in other species, we examined the immune response of the bee treated with constant low temperature, low temperature with high temperature pulse, and no treatment control. We found that both treatment groups had weakened immune responses as compared the no treatment controls.

Technical Abstract: Megachile rotundata, commonly known as the alfalfa leafcutting bee, is a key alternative pollinator. Farmers store pupal M. rotundata over the winter inside a 6°C incubator and then place the pupal bees into incubators at 29°C to initiate adult development. Their goal is to time adult bee emergence with crop blooms. Factors such as weather can delay crops from blooming. To slow down bee emergence for better timing, farmers use a treatment called static thermal regime (STR). STR is an interrupted storage treatment which the bees are taken from 29°C incubator, then placed into a 6°C incubator for a week, and afterward returned to 29°C to continue development. This delay usually results in a higher mortality rate. An alternative method to STR, fluctuating thermal regime (FTR), yields better survival. FTR is similar to STR except that when bees are at 6°C, they receive a daily one hour pulse of heat at 20°C. Although the survival rates of bees in FTR are better, we still do not know whether those bees are as healthy as untreated bees. To test how the temperature treatment affects bee immunity, we infected developing bees with E.coli. We compared untreated M.rotundata to those reared in both reared in both STR and FTR. After infecting them, we tracked their survival and development times during infection. Interrupting development with STR and FTR treatments affected survival and development times during infection. However, it is unclear from our results whether FTR or STR is better for bee health.