Location: Carl Hayden Bee Research Center
2021 Annual Report
Objectives
Obj. 1: Reduce bee colony losses from nutritional stress by determining the nutrients required to support optimum colony growth and queen health in the spring and summer, and in the fall to prepare bees for overwintering.
Sub-obj. 1A:Determine nutrient use and storage in bees through the year.
Sub-obj. 1B:Determine the seasonal balances of fatty acid nutrients required to support queen health and physiology, and worker-queen interactions linked to queen productivity and retention in the spring and summer, and in the fall prior to overwintering.
Obj. 2: Determine plant growth conditions and practices that affect the nutrient composition of nectar and pollen for bees.
Sub-obj. 2A:Determine whether cultivars of pollinator-dependent plants with known lipid profiles produce pollens with similar lipid profiles.
Sub-obj. 2B:Determine the effects of plant growth conditions on nectar and pollen secondary metabolites.
Sub-obj. 2C:Determine the effects of growth condition-dependent secondary metabolites on bees.
Obj. 3: Develop methodological and statistical tools for extracting information on bee colony health and activity from continuous sensor data, apply those methods to manipulative field experiments, and relate sensor output to colony performance.
Sub-obj. 3A:Correlate daily patterns of hive weight change, thermoregulation and CO2 levels with colony pest and disease status, environmental factors, gene expression and protein metrics.
Obj. 4: Develop Best Management Practices for placing hives in cold storage that consider nutritional needs, parasite and pathogen spread, and optimal timing to reduce colony losses.
Sub-obj. 4A:Evaluate the impact of placing bee colonies in cold storage for short periods in Sept. to Oct. with respect to colony health, survival, behavior, stress, and pest and pathogen levels.
Sub-obj. 4B:Identify the optimum timing for placing colonies in cold storage to minimize winter losses and maximize populations in spring.
Sub-obj. 4C:Compare survival and growth in the spring for colonies from different latitudes overwintered in cold storage.
Obj. 5: Determine if improved nutrition and overwintering in cold storage reduces the impact of Varroa migration on mite population and virus levels in bee colonies.
Sub-obj. 5A:Determine the relationship between mite populations and Varroa-transmitted virus levels through the year in colonies with and without supplemental pollen feeding.
Sub-obj. 5B:Determine whether a Sept. miticide treatment followed by placing colonies in cold storage in Oct. affects Varroa populations, deformed-wing virus levels, and overwintering survival.
Obj. 6: Quantify the impacts of exposure to agrochemicals on worker bees and queens, and the interactions of those agrochemicals with in-hive treatments against pests and diseases.
Sub-obj. 6A:Measure the impact of the interaction of agricultural pesticides with in-hive pest treatments on colony growth, foraging, thermoregulation and CO2 regulation.
Sub-obj. 6B:Quantify the impacts of agrochemicals and their interactions with in-hive pest treatments on queen physiology, development and replacement, and on worker-queen interactions linked to queen productivity.
Approach
Objective 1: The components of an artificial diet healthy for bees in the long term remains elusive. This project will address the roles of lipids and secondary metabolites in queen and worker bee health. Lipids are a diverse nutrient class with roles in energy production and physiological homeostasis. Essential fatty acids such as linoleic and linolenic acid, are obtained solely from pollen and needed for gland development, production of worker and royal jelly, and brood and queen rearing. How these essential lipids move through the colony and how that flux is influenced by diet will be explored.
Objective 2: Pollen and nectar contain a variety of secondary metabolites such as thymol and eugenol that are produced in response to biotic and abiotic stressors. Thymol and eugenol are broad-spectrum antimicrobials that inhibit growth of bee pathogens, and both occur in flowers, including nectar. Thymol is also used as a miticide against bee pests. This project will explore how the concentrations of these secondary compounds can be manipulated via environmental conditions, and the effects of those compounds on bee diseases and colony microbiota.
Objective 3: Monitoring colonies using sensors can reveal information on colony genetics, phenology, pesticide exposure and nutrition. Interest in monitoring colonies using sensors is increasing and with it the need to identify which kinds of data, such as weight, temperature and CO2 concentration, are most informative, and the most effective models and methods for extracting information from the data.
Objective 4: The use of cold storage is a common method to preserve and protect colonies. This project will determine whether cold storage has the potential to induce the production of diutinus bees needed for winter survival. Cold storage may also be used to control Varroa mites by inducing colonies to reduce brood production and thus allow more effective treatment of the Varroa. The project will focus on whether the value of the improved treatment efficacy exceeds the cost of the stress on the colonies by monitoring bees on the colony and individual level.
Objective 5: Varroa mites remain a major cause of bee stress worldwide; modern commercial beekeeping often involves treating colonies frequently with miticides, and placing colonies in high densities during pollination events, which puts them in contact with pests and diseases of other colonies. This project will develop recommendations to help reduce Varroa and diseases they transmit by improving colony nutrition and by exploring the application of miticides prior to cold storage to isolate colonies.
Objective 6: Agrochemical exposure is considered an important stressor for honey bees, and have been shown to affect colony growth and activity, as well as queen health. In addition, beekeepers typically apply miticides against bee pests. How these different agrochemicals interact within the hive has seldom been explored. This project will focus on monitoring queen health and worker-queen interactions, as well as sensor-based measures of colony health and behavior, in controlled field studies with field-realistic concentrations of pesticides and miticides.
Progress Report
In support of Objective 1, honey bee colonies were established and monthly collections and hive assessments are underway. Nutrient analyses are up-to-date and continue as new samples are collected. New methods for assessing queen productivity and year-round colony foraging efforts were developed.
In support of Objective 2, Brassica sp. cultivars were grown in the greenhouse and Helianthus annuus cultivars were grown in different regions and seasons in the field. Pollen was collected and analyzed for fatty acid and amino acid/protein contents. Data is being analyzed.
In support of Objective 3, research continued on the collection and analysis of bee hive sensor data, using the data to understand colony performance. A long term study was completed to understand the effects of hive direction on sensor data. In addition, two experiments were conducted to explore how changes in the bee hive itself, the use of screened bottom boards compared to solid bottom boards, can influence temperature and carbon dioxide (CO2) management within the hive. Data on both kinds of experiments are still being analyzed.
In support of Objective 4, a cold storage facility dedicated to research on honey bees was purchased and installed. The cold storage unit was equipped with sensors, fans and ducting to help manage temperature, humidity and CO2 levels. With that facility, researchers could explore the effects of cold storage on bee colony health. Placing some colonies in the facility and keeping others outside, researchers found that while a period of cold storage caused some physiological stress for the colonies, colonies kept outside, with highly variable temperatures, also showed significant signs of stress. Analysis of colony thermoregulation and CO2 management is continuing, and the experiment will be repeated in 2021.
Additionally, in support of Objective 4, colonies were selected in September 2020 in North Dakota and Texas for overwintering in colony storage. One group of North Dakota colonies was put in cold storage in October and November 2020. All Texas colonies were put in cold storage in November 2020. Colony sizes among the treatment groups were similar prior to placing them in cold storage. All colonies remained in cold storage until January 2021. When colonies were removed from cold storage for almond pollination, North Dakota colonies placed in cold storage in October or November 2020 were larger than Texas colonies. The percentage of colonies large enough for almond pollination rental also was significantly higher for North Dakota than Texas colonies. The differences between the North Dakota and Texas colonies after cold storage could be related to the physiological conditions of the bees going into cold storage, particularly the concentration of lipid and protein stored in the fat bodies of worker bees. Bees metabolize the nutrients in their fat bodies during confinement in cold storage. Bees sampled in October 2020 in North Dakota had significantly higher lipid and lower protein stores in their fat bodies than Texas bees. The change in fat body lipids during the time colonies were in cold storage was significantly related the amount of brood colonies made while in cold storage. Colony size in March after almond bloom was significantly related to the amount of brood in colonies in January 2021. Our results suggest that colonies with workers having high lipid concentrations in their fat bodies prior to cold storage overwintering produce more brood in late winter and have larger colonies in early spring.
In support of Objective 5, Varroa levels, virus levels, and overwinter survival were monitored and compared between colonies with (fed) and without (unfed) supplemental pollen. The frequency of capturing foragers with mites (FWM) was also measured at colony entrances to determine its relationship to varroa and virus levels. Colonies fed supplemental pollen from July through December were larger than unfed colonies and had higher overall survival rates. Varroa populations and levels of Deformed Wing Virus (DWV) rose throughout the season and were similar between fed and unfed colonies. Mite numbers were correlated with the frequency of capturing FWM in fed and unfed colonies, and significantly affected DWV levels. We concluded that mites entering colonies on foragers significantly increase varroa and DWV levels and may lessen the benefits that supplemental pollen feeding have on immune function. However, pollen feeding can stimulate colony growth and this can improve colony survival.
In support of Objective 6, researchers in Tucson, Arizona, conducted a field experiment on the effects of the pesticide flonicamide on bee colony health and behavior. Pesticide concentrations in the experiment were the same as those observed in the field in commercial bee colonies. Data is currently being analyzed.
Accomplishments
1. Nutrients in seasonal pollens support the annual cycle of honey bee colonies. Colony losses from malnutrition could be reduced by providing pollen sources that meet the annual nutritional needs of honey bees. ARS researchers in Tucson, Arizona, identified the nutrients in spring and fall pollen and bee responses to them. Pollens were collected in Arizona and Iowa where seasonal cycles of colony growth are similar in spring and summer, but differ in the fall and winter with brood rearing ending in Iowa and colder temperatures leading to months of confinement in the hive. Spring pollens from Arizona and Iowa had higher levels of nutrients that support brood rearing than fall pollens, and bees consuming spring pollens developed larger brood food glands for feeding the queen and rearing larvae. Fall pollen from Iowa had higher levels of fatty acids and certain amino acids needed to support colonies during confinement than pollen from Arizona. Findings are important for developing pollinator seed mixtures that provide pollen with required nutrients throughout the period when colonies are active, and in the formulation of pollen substitute diets that need to be specific for the season when they are being fed to colonies.
2. The Insect Growth Regulator (IGR) methoxyfenozide reduces sperm storage in replacement queens. The Insect Growth Regulator (IGR) methoxyfenozide is broadly used as a pesticide because it disrupts hormone balances during molting, and causes mortality in lepidopteran larvae and pupae. Methoxyfenozide has low acute (short term) toxicity against honey bee adults, larvae, and pupae; however, its long term sublethal effects against developing bees are poorly understood. ARS researchers in Tucson, Arizona, examined long term sublethal effects of methoxyfenozide exposure via contaminated pollen and wax on rearing and production of new queens from worker larvae. Methoxyfenozide-exposed colonies were able to rear and support new replacement queens of similar physiological and reproductive quality and comparable survival rates as unexposed colonies. However, queens reared in methoxyfenozide-exposed colonies stored less sperm in their spermathecae (sperm storage organ) than unexposed queens. Methoxyfenozide exposure may reduce the reproductive lifespan of the queen by limiting the production of workers from fertilized eggs, and lead to more frequent queen failure and replacement.
3. Five-year study showed a low concentration of a neonicotinoid pesticide, imidacloprid, affected honey bee colony activity, but not productivity. A five-year study by ARS researchers demonstrated that low concentrations of a neonicotinoid pesticide, imidacloprid, affected honey bee colony activity, but not productivity. Colonies fed five parts per billion of imidacloprid in sugar syrup showed increased brood production, lower temperature variability, higher CO2 production and more foragers compared to control colonies. Imidacloprid consumption did not affect adult bee numbers or average hive temperatures, and did not decrease food stores, daily food acquisition or colony survivorship. These results suggest that imidacloprid contamination increased colony metabolism without improving colony productivity, and helps explain why some studies have reported no, or even positive, effects of neonicotinoids on honey bee colony health. Variability in weather, particularly rainfall, added considerably to the variability in the experiment in general.
Review Publications
Hoffman, G.D., Corby-Harris, V.L., Carroll, M.J., Toth, A., Gage, S., Watkins De Jong, E.E., Graham, R.H., Chambers, M.L., Meador, C., Obernesser, B. 2021. The importance of time and place: Nutrient composition and utilization of seasonal pollens by European honey bees (Apis mellifera L.). Insects. 12(3). Article 235. https://doi.org/10.3390/insects12030235.
Colin, T., Forster, C.C., Westacott, J., Wu, X., Meikle, W.G., Barron, A.B. 2021. Effects of late miticide treatments on foraging and colony productivity of European honey bees (Apis mellifera). Apidologie. 52:474-492. https://doi.org/10.1007/s13592-020-00837-3.
Meikle, W.G., Adamczyk Jr, J.J., Weiss, M., Ross, J.F., Werle, C.T., Beren, E.D. 2021. Sublethal concentrations of clothianidin affect honey bee colony growth and hive CO2 concentration. Scientific Reports. 11. Article 4364. https://doi.org/10.1038/s41598-021-83958-8.
Fine, J.D., Corby-Harris, V.L. 2021. Beyond brood: the potential impacts of insect growth disruptors on the long-term health and performance of honey bee colonies. Apidologie. 52:580-595. https://doi.org/10.1007/s13592-021-00845-x.
Rodriguez-Garcia, C., Heerman, M.C., Cook, S.C., Evans, J.D., Hoffman, G.D., Banmeke, O.A., Zhang, Z., Huang, S., Hamilton, M.C., Chen, Y. 2021. Transferrin-mediated iron sequestration suggests a novel therapeutic strategy for controlling Nosema disease in the honey bee, Apis mellifera. PLoS Pathogens. 17(2):e1009270. https://doi.org/10.1371/journal.ppat.1009270.
Fisher Ii, A., Hoffman, G.D., Smith, B., Ozturk, C., Kaftanoglu, O., Fewell, J., Harrison, J. 2021. Field cross-fostering and in vitro rearing demonstrate negative effects of both larval and adult exposure to a widely used fungicide in honey bees (Apis mellifera). Ecotoxicology and Environmental Safety. 217. Article 112251. https://doi.org/10.1016/j.ecoenv.2021.112251.
Hoffman, Gloria D., Corby-Harris, Vanessa L., Chen, Yanping, Graham, Henry, Chambers, Mona L., Watkins De Jong, Emily E., Ziolkowski, Nicholas F., Kang, Yun, Gage, Stepanhie L., Deeter, Megan E., Simone-Finstrom, Michael, De Guzman, Lilia, I. 2020. Can supplementary pollen feeding reduce varroa mite and virus levels and improve honey bee colony survival?. Experimental and Applied Acarology. 82:455-473. https://doi.org/10.1007/s10493-020-00562-7.
Glass, J.R., Fisher, A., Fewell, J.H., Hoffman, G.D., Ozturk, C., Harrison, J.F. 2021. Consumption of field-realistic doses of a widely used mito-toxic fungicide reduces thorax mass but does not negatively impact flight capacities of the honey bee (Apis mellifera). Environmental Pollution. 274. Article 116533. https://doi.org/10.1016/j.envpol.2021.116533.
Desjardins, N., Fisher, A., Ozturk, C., Fewell, J., Hoffman, G.D., Harrison, J., Smith, B. 2021. A common fungicide, Pristine®, impairs olfactory associative learning performance in honey bees (Apis mellifera). Environmental Pollution. 288. Article 117720. https://doi.org/10.1016/j.envpol.2021.117720.
