The survival and growth of honey bee (Hymenoptera: Apidae) colonies overwintered in cold storage: the effects of time and colony location

Authors: DeGrandi-Hoffman, Gloria; Corby-Harris, Vanessa; GRAHAM, R.H. - Retired ARS Employee; Watkins De Jong, Emily; Chambers, Mona; Snyder, Lucy

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/24/2023
Publication Date: 6/19/2023
Citation: Hoffman, G.D., Corby-Harris, V.L., Graham, R., Watkins De Jong, E.E., Chambers, M.L., Snyder, L.A. 2023. The survival and growth of honey bee (Hymenoptera: Apidae) colonies overwintered in cold storage: the effects of time and colony location. Journal of Economic Entomology. 116(4):1078-1090. https://doi.org/10.1093/jee/toad103.
DOI: https://doi.org/10.1093/jee/toad103

Interpretive Summary: Over the past decade, annual losses of managed colonies over the winter have exceeded 30% causing beekeepers to explore alternative management strategies including wintering bees in cold storage facilities. We investigated factors that could affect the survival and size of colonies overwintered in cold storage and then used for California almond pollination in February. The factors were the time during the fall when hives were put into cold storage, and the geographic location of colonies prior to overwintering. We placed hives that were in North Dakota, USA during the summer into cold storage facilities in either October (ND-Oct) when colonies contained adult bees and sealed brood or November (ND-Nov) when there were only adult bees. Both groups were similar in size in October, but ND-Nov lost an average of 1.5 frames with bees between October and when they went into cold storage in November. ND-Nov also were smaller after cold storage and almond bloom compared with ND-Oct. The location of colonies prior to overwintering also affected their size and survival after cold storage and almond bloom. Colonies that summered in southern Texas, USA (TX-CS) and were put into cold storage in November had smaller adult populations and less brood after cold storage and almond pollination than those from North Dakota (ND-Nov). Colonies that remained in Texas apiaries for the winter were larger than the TX-CS. The physiological state of the bees when moved to cold storage, particularly the concentrations of nutrients stored in their fat bodies, may have affected colony size after overwintering. Honey bees store nutrients (e.g., protein and lipids) in their fat bodies in the fall in preparation for confinement in the hive over the winter. Fat bodies in ND-Oct and ND-Nov had higher lipid and lower protein concentrations than TX-CS. Fat bodies gained weight while bees were in cold storage. Protein concentrations increased, while lipid concentrations decreased in ND-Oct and ND-Nov but not TX-CS. The decrease in fat body lipid levels was correlated with the amount of brood reared while colonies were in cold storage. Colony sizes after almond bloom were correlated with brood area after cold storage. Our study indicates that colonies in northern latitudes might have larger populations after overwintering if they are put into cold storage when they contain sealed brood and adult bees. Results also indicate that colonies summered in southern latitudes should be overwintered there rather than in cold storage facilities.

Technical Abstract: High losses of managed colonies have caused beekeepers to explore alternative overwintering strategies including putting hives in cold storage facilities. We explored factors that could affect the survival and size of colonies overwintered in cold storage and then used for California almond pollination in February. The factors were the time during the fall when hives were put into cold storage, and the geographic location of colonies prior to overwintering. We placed colonies that were in North Dakota, USA during the summer into cold storage facilities in either October (ND-Oct) or November (ND-Nov). Both groups were similar in size in October, but ND-Nov lost on average 1.5 frames with bees between October and November when hives entered cold storage. ND-Nov colonies also were smaller after cold storage and almond bloom compared with ND-Oct. The location of colonies prior to overwintering also affected their size and survival after cold storage and almond bloom. Colonies that summered in southern Texas, USA (TX-CS) and were put into cold storage in November had smaller adult populations and less brood after cold storage and almond pollination than those from North Dakota (ND-Nov). Colonies that remained in Texas apiaries for the winter were larger than the TX-CS. The physiological state of the bees entering cold storage may have affected colony size after overwintering. Fat bodies in ND-Oct and ND-Nov had higher lipid and lower protein concentrations than TX-CS. Fat bodies gained weight while bees were in cold storage, and protein concentrations increased, and lipid concentrations decreased in ND-Oct and ND-Nov but not TX-CS. The decrease in fat body lipid levels was correlated with the amount of brood reared while colonies were in cold storage, and brood rearing was correlated with colony populations after almond bloom. Our study indicates that colonies in northern latitudes might have larger populations after overwintering if they are put into cold storage when they contain sealed brood and adult bees. Results also indicated that colonies summered in southern latitudes should be overwintered there rather than in cold storage facilities.