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United States Department of Agriculture

Agricultural Research Service

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Location: Honey Bee Research

2013 Annual Report

1a. Objectives (from AD-416):
1: Determine the nutrients in pollen that promote worker longevity. 1.A. Determine the effects of pollen mixtures on worker protein and lipid stores and longevity. 1.B. Characterize the chemical composition of pollen mixtures that optimize worker protein and lipid stores and longevity. 2: Determine the effects of undigested saccharides in high fructose corn syrup (HFCS) on worker physiology and longevity. 2.A. Identify the saccharides in HFCS. 2.B: Determine the effect of saccharides in HFCS on worker physiology and longevity. 3: Evaluate the effects of supplemental feeding on Varroa tolerance, queen production and foraging activity of honey bee colonies. 3.A. Modify the MegaBee diet by adding chemical components that were identified in the pollen mixture analysis. 3.B. Determine the effects of nutrition on Varroa infestation and reproduction in worker and drone cells. 3.C. Determine the role of nutrition on queen production and reproductive potential. 3.D. Evaluate the effects of supplemental protein feeding on the foraging rates of honey bee colonies. 3.E. Improving honey bee immune response to CCD by determining the role of symbiotic microbes in bee nutrition. 3.F. Develop IPM tools (e.g., "soft" miticides that are non-toxic to workers and queens, traps, and exclusion devices) and methodologies for control of key pests (especially Varroa mites), and miticide resistance management programs to preserve useful chemical options. 3.G. Determine the impact of the small hive beetle on colony development and longevity, and develop management systems for controlling the beetle in hives, including use of antifeedants for protection of protein supplements from small hive beetle damage. Develop effective control programs for management of small hive beetle in bee hives, with the goal to prevent contamination of bee products.

1b. Approach (from AD-416):
1. Nutritional value will be evaluated by measuring protein and lipid levels and on bee longevity. The chemical composition of pollens that are more nutritious than MegaBee will be determined. 2. Determine the effects of high fructose corn syrup containing higher saccharides on honey bee longevity. 3. Determine the effects of improved nutrition of the longevity of bees parasitized by Varroa, the reproductive potential of queens, and foraging activity of colonies used for pollination. REPLACING 5342-21000-014-00D (8/08). FY09 Program Increase $270,000. FY10 Program Increase $315,000.

3. Progress Report:
This project is currently undergoing NP305, Crop Production, Office of Scientific Quality Review. Our research focused on the effects of nutrition on colony growth, physiology, and vulnerability to disease and parasitism. We also investigated symbiotic microbes and their function in food storage and digestion. We found that colonies fed the protein supplement diet formulated by ARS researchers in Tucson grew at comparable rates to those fed pollen. Hemolymph protein titers and hypopharyngeal glands also were comparable to those in bees fed pollen. We found that virus titers are associated with protein availability. Virus titers were lower in bees fed pollen or our diet than in those fed only sugar syrup. Nutrition influences queen supersedure and the production of queen-associated volatile compounds. During pollen shortages, there are significantly more attempts by workers to replace queens compared with when colonies are well fed. Supersedure attempts were accompanied by declines in the production of a volatile pheromone (E)-ß-ocimene, a key regulator of colony nutrition. We found that the nutritional value of pollen differs from the bee bread made from it. In general, protein values are lower in bee bread than in pollen but most amino acid levels are higher. Evaluating the nutritional value of pollen should include the bee bread made from it. Beekeepers feed colonies sugar syrup made with high fructose corn syrup (HFCS) when flowering plants are not available. We found that bees lived longer when fed sucrose compared with undiluted HFCS-55 (55% HFCS). Hydroxymethylfurfural (HMF), a heat-formed contaminant of HFCS that is toxic to honey bees was found in HFCS samples supplied to us by beekeepers. HMF forms rapidly at high temperatures and mortality rates of bees feeding on HFCS with HMF at any concentration was significantly higher than the sucrose controls. We examined the effects on queen emergence and virus titers when bees feed on pollen contaminated with sublethal levels of pesticide. Fewer queens emerged in colonies fed pollen contaminated with chlorpyrifos and emergence rates were even lower when the fungicide Pristine® was added. Deformed wing virus and black queen cell virus were found in queen larvae and emerged queens. The results suggest that sublethal exposure of chlorpyrifos alone but especially when Pristine® is added reduces queen emergence possibly due to compromised immunity in developing queens. Symbiotic microbes are essential for preserving pollen in the hive and converting it to bee bread. We found that the most abundant bacteria in stored pollen and in the bee’s crop are found in flowers. A subset of these bacteria is responsible for preserving bee bread and inhibiting the growth of pathogens in the colony. The results are important for understanding the role that microbes collected with nectar and pollen have in food processing and nutrient acquisition in the colony. The results also indicate that colony health and susceptibility to disease might be affected by environmental contaminants that inhibit the presence or growth of these beneficial microbes.

4. Accomplishments
1. New challenges in controlling Varroa mites. Varroa mites are a major cause of colony losses because they parasitize bees and spread viruses in the colony. ARS bee researchers in Tucson, Arizona, devised a treatment schedule to control Varroa based on colony and Varroa population dynamics. We found that Varroa populations could be kept at low levels throughout most of the summer with this treatment schedule. By fall though, mite populations were much larger than predicted or could be accounted for by mite reproduction alone. Varroa appears to have become migratory and move between colonies with far greater frequency than previously supposed. This finding caused us to change recommendations on Varroa control to include a late fall treatment so that mite populations remain low over the winter so that colonies will not be lost in the spring.

2. Overwintered beebread contains a comprehensive nitrogen-processing bacterial community. Overwintered beebread (pollen stored in cells for future colony growth) contains bacterial communities that cause a rapid degradation of beebread. These bacteria include those capable of digesting complex plant polymers (e.g. cellulose, pectin), providing access to the pollen protoplasm. The release of nitrogen rich cell contents of pollen is evidenced by the strong presence of a comprehensive nitrogen processing bacterial community (NPC). These NPC are present at much lower levels in corbicular pollen, suggesting that these bacterial groups are ubiquitous and continuously vectored from plants and the general pollination environment. These findings indicate a microbial connection between the environment and the preservation and nutritive value of beebread in the hive.

3. Crop bacteria of honey bee foragers is dominated by Acetobacteraceae Alpha 2.2, a non-gut bacteria also prevalent in larvae, beebread and honey. Bacteria associated with the pollination environment or floral nectar in particular, may play a major role in pollinator fitness. We used next generation amplicon sequencing to investigate bacteria communities from the honey bee gut, crop and corbicular pollen. Our results reveal that the most abundant bacteria found in corbicular pollen and the crop is Alpha 2.2, an Acetobacteraceae. We suggest that this bacteria is a mutualist involved in preserving beebread and inhibiting the growth of larval pathogens. The results are important for understanding the contribution to pollinator health of both environmentally vectored and core microbiota, and in identifying factors that may affect colony food storage and disease susceptibility.

4. Increased queen losses and disruption of queen pheromone release in pollen-starved colonies. ARS researchers at Tucson, Arizona, examined the effects of pollen deprivation on queen retention, pheromone production, and colony survival in honey bee colonies preparing for overwintering. Colonies were deprived of pollen during the production of overwintering bees. The colonies immediately ceased brood rearing and lost adult workers before disappearing entirely over a four week period. In pollen-deprived colonies, populations of older adult workers dwindled rapidly despite the presence of abundant brood and nectar stores. Queens from pollen-deprived colonies were attended by fewer workers and released lower amounts of the pheromone cis-ß-ocimene than pollen-fed queens. These results demonstrate that colony stressors such as pollen malnutrition can destroy honey bee colonies by damaging the social cohesion of colonies in addition to effects on individual workers.

5. A rapid, non-destructive method for the quantification of Queen Mandibular Pheromone (QMP) emissions from honey bee queens. ARS researchers at Tucson, Arizona, developed a rapid, non-destructive method for the quantification of QMP emissions from honey bee queens. As the primary signal of a mated queen, QMP pheromones are used by worker bees to detect and replace failing or missing queens. Previous methods require destructive extraction of the mandibular glands to provide an estimate of QMP contents in the glands. By contrast, our method allows for the repeated, measurement of QMP release rates using pheromone exchange between the queen and her workers. Researchers can use this technique to track the effects of colony stressors (i.e. malnutrition, age, disease, agrochemicals) on QMP emissions in individual queens over time. This method will be used to determine the contributions of colony stressors to the excessive queen losses and premature queen replacements widely observed in the beekeeping industry.

6. Bacteria Alpha 2.2 genome sequencing reveals a reduced Acetobacteraceae genome well-evolved for life in the honey bee hive. The genome of Alpha 2.2 was sequenced to gain an understanding of its metabolic capabilities, and potential as a probiotic organism. A comparative genomics approach suggests that Alpha 2.2 has undergone substantial gene reduction while transitioning into an intimate functional relationship with its honey bee host. Alpha 2.2 possesses Aquaporin Z, a highly stable transmembrane protein channel that facilitates rapid osmoregulation, and resists denaturing due to voltage, heat, detergent, or extremes of pH. Alpha 2.2 possesses genes involved in biofilm production that may protect larva from infection and beebread from spoilage. There is potential for use in colonies through prebiotic or probiotic application.

7. In developing honey bee nurses, hypopharyngeal gland gene expression is largely unaffected by protein starvation. Commercial honey bees are subject to periods of nutritional stress and these are implicated in colony losses. We characterized diet-dependent differences in honey bee hypopharyngeal gland gene expression using whole transcriptome analysis. Expression in nurse bees fed pollen and honey differed little from those fed only honey. This research will contribute to our understanding of the genetic and physiological changes that occur due to malnutrition associated with commercial beekeeping practices, perhaps suggesting changes in food supplements and their application.

8. High Fructose Corn Syrup (HFCS) and Colony Health. When flowering plants are unavailable, beekeepers feed colonies HFCS. We found significantly larger adult bee populations in colonies fed sucrose syrup compared with those fed HFCS. This finding complements earlier studies showing shorter lifespans in worker bees fed HFCS compared with sucrose. For commercial beekeepers, feeding HFCS instead of sucrose might reduce colony populations and leave them more vulnerable to loss from environmental fluctuations, parasites and pathogens.

Review Publications
Sammataro, D., Weiss, M. 2013. Comparison of productivity of colonies of honey bees, Apis mellifera, supplemented with sucrose or high fructose corn syrup. Journal of Insect Science. 13:19.

Hoffman, G.D., Ahumada, F., Probasco, G., Shantz, L. 2012. The effects of beta acids from hops (Humulus lupulus L.)on mortality of Varroa destructor (Acari: Varroidae). Experimental and Applied Acarology. 58:407-421. DOI:10.1007/s10493-012-9593-2.

Hoffman, G.D., Eckholm, B., Huang, M.H. 2012. A comparison of bee bread made by Africanized and European honey bees (Apis mellifera) and its effects on hemolymph protein titers. Apidologie. 44:52-63 DOI:10.1007/s13592-012-0154-9.

Carroll, M.J., Duehl, A.J. 2012. Collection of volatiles from honey bee larvae and adults enclosed on brood frames. Apidologie. 43: 715-730. doi: 10.1007/s13592-012-0153-x.

Donaldson-Matasci, M., Hoffman, G.D., Dornhaus, A. 2013. Bigger is better: honey bee colonies as distributed information-gathering systems. Journal of Animal Behavior. 85(3), 585-592.

Hoffman, G.D., Chen, Y., Simonds, R. 2013. The effects of pesticides on queen rearing and virus titers in honey bees (Apis mellifera L.). Insects. 4(1), 71-89.doi:10.3390/insects4010071.

Last Modified: 05/25/2017
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