The economics of honey bee (Hymenoptera: Apidae) management and overwintering strategies for colonies used to pollinate almonds

Authors: DeGrandi-Hoffman, Gloria; Graham, Richard; AHUMADA, FABIANA - Betatec Hop Products Inc; SMART, MATHEW - University Of Nebraska; Ziolkowski, Nicholas

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/15/2019
Publication Date: 9/3/2019
Citation: Hoffman, G.D., Graham, R.H., Ahumada, F., Smart, M., Ziolkowski, N.F. 2019. The economics of honey bee (Hymenoptera: Apidae) management and overwintering strategies for colonies used to pollinate almonds. Journal of Economic Entomology. 112(6):2524-2533. https://doi.org/10.1093/jee/toz213.
DOI: https://doi.org/10.1093/jee/toz213

Interpretive Summary: Pollination services by commercial honey bee colonies are key contributors to agricultural productivity. No crop requires more colonies for pollination than almonds in California. Costs of managing and transporting honey bee colonies to California have increased as have colony losses that can exceeded 30%. Though rental fees for colonies also have increased, we asked if renting colonies for almond pollination was a profitable venture. To address this question, we conducted a longitudinal study on 190 colonies from when they were established in April until they were placed in almond orchards 10 months later. Two overwintering methods were compared on equal numbers of colonies. Colonies were placed either in cold storage (CS) facilities or in outdoor apiaries for the winter. During the study period, we recorded colony and Varroa population sizes and all costs incurred by the beekeeper including those for overwintering in CS and in apiaries. The cost of overwintering in CS was lower than in apiaries, but fewer CS colonies were large enough for almond pollination rental. We found that in colonies overwintered in CS the size and Varroa mite populations in September significantly affected whether the colonies would be large enough for almond pollination in February. This relationship was not significant for colonies overwintered in apiaries. We also found that the cost of maintaining colonies from September to almond bloom exceeded colony rental fees whether colonies were in CS or apiaries. Our only profitable venture was honey production in the summer. We propose alternative management strategies that could lower costs and make almond pollination profitable. The strategies rely on placing colonies in CS earlier in the fall, lowering Varroa populations and increasing forage availability. In addition, we developed a decision matrix containing probabilities of CS colonies reaching sizes sufficient for almond pollination based on their size and mite numbers in September. This information is useful for selecting colonies to overwinter and reducing expenditures for hives that are unlikely to reach sufficient size for almond pollination. Though there is little or no profit in renting colonies for almond pollination at current prices, the abundant nutritional resources available to bees during almond bloom enable colonies to build. The colonies then can generate revenue through honey production later in the summer if sufficient forage is available. CS can lower overwintering costs and improve colony survival, but best management practices are needed to improve decision-making and reduce risk for beekeepers.

Technical Abstract: Commercial honey bee colonies are significant contributors to agricultural productivity through the pollination of crops. Almonds need the greatest number of colonies because the nearly one million acres of bearing trees require cross pollination for nut set. For more than a decade, beekeepers have experienced colony losses in excess of 30%, mostly during the winter. With the costs of managing and transporting honey bee colonies to California, combined with the colony losses beekeepers routinely experience, we asked if renting colonies for almond pollination was a profitable venture. To address this question, we conducted a longitudinal study on 190 colonies from when they were established in April until they were placed in almond orchards 10 months later. Two overwintering methods were compared on equal numbers of colonies. Colonies were placed either in cold storage (CS) facilities or in outdoor apiaries for the winter. We recorded all costs incurred by the beekeeper throughout the study and added them to the costs of the two overwintering methods. For colonies overwintered in CS, the size of colonies and Varroa mite (Varroa destructor Anderson and Trueman) populations in September significantly affected whether the colonies would be large enough in February for almond pollination. This relationship was not significant for colonies overwintered in apiaries. The cost of overwintering in CS was lower than in apiaries, but fewer CS colonies were large enough for almond pollination rental. The cost of maintaining colonies from September to almond bloom exceeded colony rental fees whether colonies were in CS or apiaries. Our only profitable venture was honey production in the summer. We propose alternative management strategies that could lower costs and make almond pollination profitable, but they rely on placing colonies in CS earlier in the fall, lowering Varroa populations and increasing forage availability. In addition, we developed a decision matrix containing probabilities of CS colonies reaching sizes sufficient for almond pollination based on their size and mite numbers in September. This information is useful for selecting colonies to overwinter and reducing expenditures for ones that are unlikely to reach sufficient size for almond pollination. A key finding from our study is that there is little or no profit in renting colonies for almond pollination at current prices once summer management and overwintering costs are considered. However, the abundant nutritional resources available to bees during almond bloom enable colonies to build and generate revenue through honey production later in the summer if there is sufficient forage. Our study indicates that CS can lower overwintering costs and improve colony survival, but best management practices are needed to improve decision-making and reduce risk for beekeepers.