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Research Project: Determining the Impacts of Pesticide- and Nutrition-Induced Stress on Honey Bee Colony Growth and Survival

Location: Honey Bee Research

Title: Honey bee colonies provided with natural forage have lower pathogen loads and higher overwinter survival than those fed protein supplements

Author
item Degrandi-hoffman, Gloria
item Chen, Yanping - Judy
item Rivera, Raul
item Carroll, Mark
item Chambers, Mona
item Hidalgo, Geoffrey
item Watkins De Jong, Emily

Submitted to: Apidologie
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/14/2015
Publication Date: 8/4/2015
Publication URL: http://handle.nal.usda.gov/10113/61776
Citation: Hoffman, G.D., Chen, Y., Rivera, R., Carroll, M.J., Chambers, M.L., Hidalgo, G., Watkins De Jong, E.E. 2015. Honey bee colonies provided with natural forage have lower pathogen loads and higher overwinter survival than those fed protein supplements. Apidologie. doi: 10.1007/s13592-015-0386-6.

Interpretive Summary: Good nutrition is a fundamental component in the health and longevity of all organisms. In honey bees, all nutritional needs are met with nectar and pollen. Nectar provides carbohydrates while pollen supplies protein and all other nutrients. Pollen is essential for colony growth and survival, but there are periods when bees are active and pollen is not available. In managed colonies, shortages of pollen are alleviated by feeding protein supplements. Supplements typically are fed to colonies in the spring. However, feeding colonies in the fall and through the winter has become increasingly common especially for hives used in pollination of almonds. Recently land managers have been encouraged to increase plantings of bee forage to provide pollen for colonies used in almond pollination. However, do these plantings improve colony health and survival to greater degree than those receiving adequate amounts of commercially available PS? We addressed this question by either placing colonies near fields of a blooming fall mustard called rapini (Brassica rapa) or feeding colonies commercially available protein supplements (e.g., diet-1 or -2) in areas without blooming plants from November to February. We found that the protein supplements had lower levels of protein and certain amino acids than rapini pollen, and were not digested as well. Though colony size did not differ between those foraging on rapini and fed protein supplement, colony losses were twice as high in those fed the supplements. Queen losses also were higher in colonies fed diet-1 than in those fed diet-2 or foraging on rapini. Some of the losses might have been due to Nosema or virus. These pathogens were found at higher levels in colonies fed the supplements than in those foraging on rapini. Our study indicates that queen and colony losses might be reduced if some forage was available to bees prior to almond bloom.

Technical Abstract: Symptoms of nutritional stress can manifest in several ways, including higher incidence of disease in stressed individuals. Honey bees experience nutritional stress when there is insufficient forage. During these times, managed colonies are fed protein supplements (PS). Recently, land managers have been encouraged to plant bee forage to provide pollen sources. If bees are exposed to natural forage rather than fed a steady supply of PS, will colonies have lower levels of pathogens and higher survival rates? We addressed this question by either placing colonies near fields of a blooming fall mustard called rapini (Brassica rapa) or feeding colonies commercial PS (diet-1 or -2) in areas without blooming plants from November to February. The protein content in diet-1 and 2 was lower than the rapini pollen as were levels of the amino acids histidine, isoleucine, valine, proline and cysteine particularly in the case of diet-1. Nurse bees from colonies fed PS had higher concentrations of protein in the undigested contents of their hindguts than those foraging on rapini suggesting that the bees more readily digested the protein in the pollen compared with the PS. There was no difference in hemolymph protein titers or colony growth between those fed PS or foraging on rapini. However, colonies fed the commercial PS particularly diet-1, had higher incidence of Black Queen Cell Virus and Nosema and greater queen losses. The study indicates that PS might not provide all the nutrients colonies need to maintain low levels of pathogens and prevent queen loss, and colonies might benefit from having natural forage available.