Location: Carl Hayden Bee Research Center
2022 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 Sub-objective 1A, field experiments were conducted in fiscal year (FY) 2021 and completed in FY22. Fifty colonies were established in two different apiaries and were measured monthly for brood and adult population size. Samples were obtained to measure nutrients (total protein and lipid) in brood nest bee (BNB) and forager (F) fat bodies, corbicular pollen (CP) and stored pollen (SP), larvae, drones, and supersedure queens. Colony population data from year 1 is analyzed. Nutrient levels were measured in the BNB and F fat bodies and CP, and the data are analyzed for year 1. Larvae are collected and are partially analyzed. In year 2, another 50 colonies were established and are being monitored as above. Monthly sampling is on schedule. The year 2 samples are partially analyzed, and this will continue through the end of FY22 into FY23. With respect to Experiment 2 planned for year 2, the first two years of data will determine when to conduct these cage experiments. The first trials are planned for the end of FY22. Fall and early winter are emerging as crucial periods where colonies prepare for a winter-like state in southern Arizona.
In support of Sub-objective 1B, field colonies were treated (+/-) with supplemental pollen patty during a seasonally critical period (early fall/pre-overwintering preparation) and monitored through the spring for queen performance. Supplemental nutrition was not a factor among colonies due to abundant forage after an exceptionally wet summer. Both treatment groups experienced heavy colony losses (74%) due to biotic factors including invasion swarms, queen supersedures, robbing, and Varroa mites. Queen losses were much higher than average, suggesting that risks of queen usurpation are higher in forage-rich years. Treatment groups did not differ in population size, brood rearing, or worker quality, indicating that fall supplementation was not a limiting factor. Queen pheromone and physiological metrics are being analyzed. Experiment 1 will be repeated twice in successive years to provide results under typical forage-limited fall conditions, moving our year 3 milestone forward by one year.
In support of Sub-objective 2A, pollen and seed from the year 1 planting (30 Brassica sp. (canola) cultivars) were analyzed for fatty acid content. The same 30 lines of canola were grown in the greenhouse in year 2. The pollen was collected from all lines and stored for subsequent analysis. A freezer failure destroyed the year 2 pollen samples. We will repeat the year 2 planting in FY23 and push the year 3 milestone forward one year.
In support of Sub-objective 3A, a second experiment on the characterization of different queenliness, by monitoring colony-level behavior, is being conducted comprising two commercial queen lines from California, and the USDA Pol-Line and Russian lines, in collaboration with ARS researchers in Baton Rouge, Louisiana. Hive weight, temperature and carbon dioxide (CO2) concentrations are being monitored for nine months, with colonies being regularly assessed for adult bees and brood, and worker bee samples taken for physiological parameters. A subset of each line will be monitored in cold storage over winter. A novel monitoring device, developed by researchers at Utah State University, Logan, Utah, is being tested on two queenlines to assess flight activity as a line-specific character. Another novel device, a photonic fence, was donated to our project for collaborative work with an ARS researcher from Ft. Pierce, Florida. A photonic fence tracks and records all flying insects in a given volume of space. Investigations on the effects of changes in hive ventilation characteristics on internal CO2 concentration and air cycling continued with further experiments, and a paper has been prepared and accepted. Finally, a set of field experiments to evaluate a novel algae-based diet has been completed, in collaboration with ARS researchers at Baton Rouge, Louisiana. Response variables include measures of worker bee health, such as vitellogenin levels, gene expression, and colony-level growth and behavior. Artificial diet using algae was found to perform as well as a commercial diet with respect to colony growth and thermoregulation.
For Sub-objective 4A, a study was repeated to determine how a treatment of 3 weeks of cold storage combined with miticide might affect colony health and mite levels. Results showed that, immediately after cold storage honey bees had significantly higher levels of stress-associated malondialdehyde than bees kept outside but another stress marker, protein carbonyl, was unaffected. None of the six genes evaluated, including vitellogenin, antioxidant enzymes and thermal stress responses, showed significant effects of cold storage. Because of abundant bee forage, colonies in 2021 were almost three times larger before cold storage than in 2020, and in 2021 colonies increased adult bee mass by about 9% during cold storage while outside colonies lost 36% during that same period. In contrast, in 2020 colonies lost 29% of their adult bee mass in cold storage, compared to 18% for colonies kept outside. By February in both years colonies from cold storage had lost on average 80% of their bees while outside colonies had lost 60%. Mite levels in February were more affected by miticide than cold storage. Data on brood levels, hive weight, temperature and internal CO2 are still being analyzed.
In support of Sub-objective 4B, we investigated factors that could affect colony size and survival after cold storage overwintering. The factors were when hives are put into cold storage, and the geographic location of colonies prior to overwintering. Our colony population model predicts that putting colonies in cold storage in October would ensure greater colony size and survival after cold storage then waiting until later in the fall. To test this, we put colonies that were in North Dakota during the summer, in cold storage in either October (ND-Oct) or November (ND-Nov). Both groups of colonies were similar in size in October, but ND-Nov lost an average of 1.5 frames with bees between October and November. 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 (TX-CS) had smaller adult populations and less brood after cold storage and almond pollination than those from North Dakota. The physiological state of the bees just prior to cold storage may have affected colony size after cold storage. Fat body composition in TX-CS bees differed from ND-Oct and ND-Nov with higher lipid and lower protein concentrations in ND colonies. While the colonies were in cold storage, lipid levels decreased, and protein increased in ND-Oct and ND-Nov bees. The decrease in fat body lipid levels was correlated with the amount of brood reared while colonies were in cold storage, and this in turn 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 in October. Results also indicated that colonies summered in southern latitudes should be overwintered there rather than in cold storage facilities.
In support of Sub-objective 4C, a study was conducted to determine if treatments for the gut pathogen Nosema ceranae prior to putting colonies in cold storage affected colony size after cold storage and almond bloom. Colonies located in North Dakota apiaries were treated for Nosema infections in October prior to cold storage overwintering. A second group of colonies received no treatment. Nosema spore counts were taken in all colonies prior to treatment and again after overwintering. Data comparing colony sizes and survival and Nosema levels after overwintering are under analysis.
Progress on Objective 5 included studies to identify possible cues foragers carrying Varroa mites might use to select a colony to enter. We hypothesized that the cues would be volatile and may be associated with a laying queen and brood since mites reproduce in brood cells. Furthermore, foragers with mites are younger worker bees that might respond to brood odors since younger bees care for brood. To test if brood odors affect the frequency of capturing foragers with mites at colony entrances, we established sets of colonies with frames of open brood, caged queens and no brood, and colonies with wicks containing the volatile brood pheromone, ocimene. Ocimene emanates from laying queens and young uncapped brood and signals their presence in a colony. Data were collected on the frequency of collecting foragers with mites in the three treatment groups and is currently under analysis.
In support of Sub-objective 6A, a field experiment and two cage studies on the effects of sublethal exposure of another agricultural pesticide, flonicamid, on bee colony growth and behavior have been conducted and the data analyzed. We had detected flonicamid at comparatively high levels in commercial apiaries. A manuscript was prepared and is in internal review.
In support of Sub-objective 6B, we closely examined sublethal effects of amitraz and chlorpyrifos on queens over a range of agrochemical field exposures before conducting large scale field experiments. Recent studies report that retinue workers exposed to higher-than-average field exposures of amitraz and chlorpyrifos reduce queen care while amitraz slowed queen oviposition and reduced queen larval care. We developed novel visualization techniques (EthoVision queen tracking, fluorescent illumination of eggs and larvae) to separate sublethal effects on queens from those on attendant retinue workers. We are currently collecting data from observation colonies to determine if effects occur at more field-realistic exposures.
Accomplishments
1. Improving the management of honey bee colonies overwintered in cold storage. Every year more honey bee colonies are overwintered in cold storage to reduce losses that have averaged 40% during this time of year. However, beekeepers need to know when to put colonies in cold storage. They also need to know if colonies from different regions of the United States, especially the southern states, do equally well as colonies from temperate regions when overwintered in cold storage. ARS researchers in Tucson, Arizona, found that colonies summered in northern latitudes and put into cold storage by mid-October were larger and had more brood after cold storage and after almond pollination than those put into cold storage in November. They also found differences in physiological markers between bees from northern and southern latitudes suggesting that colonies that summer in southern latitudes do not convert into functional winter bees that can survive long periods of confinement in the hive. When overwintered in cold storage, colonies from southern latitudes were smaller and had lower survival rates after cold storage and almond bloom than those from northern latitudes.
2. Increasing our understanding of CO2 concentration in bee hive. The use of sensors in bee hives is increasing as a research tool to understand the relationship between bee colonies, their environment, and the effects of stressors and management practices. Carbon dioxide (CO2), a byproduct of respiration, is toxic at high concentrations, so controlling CO2 within the hive is an important colony function. To help understand factors that affect CO2 concentration, ARS researchers in Tucson, Arizona initiated an experiment where sensors measured CO2 at 15 second intervals for hives with screened and solid bottom boards. Although ventilation increased with screen bottom boards, average CO2 concentrations rose higher, rather than dropped, indicating that CO2 concentration was not simply a function of ventilation. Colony temperature and foraging activity were unaffected by the change in bottom boards. Although bee colonies have been reported to cycle air within the hive, with shorter periods of 20 to 150 seconds and longer periods of 42-80 minutes, researchers found no evidence of significant CO2 cycle periods other than a strong 24 hour period. Bee colonies in the study maintained average maximum concentrations greater than 11,000 parts per million, even with increased ventilation, indicating that the relationship of bee colonies to CO2 concentration is complex. Data on CO2 concentration may include information on colony health.
3. Increasing our knowledge of how colony nutrients change over time. Natural and supplemental diets that are available to hives throughout the year must meet the colony’s nutritional needs, as poor nutrition compromises colony health. ARS researchers in Tucson, Arizona, characterized the nutrients that are stored and utilized by the bee during key seasonal changes in the colony (Experiment 1). They concluded that macronutrients like total lipid and protein correlate with seasonal patterns of hive growth and contraction. This information allows researchers to address the secondary goal of this work, which is to determine whether existing supplements meet these seasonal nutrient needs (Experiment 2). Many of these focal nutrients (lipids, proteins, fatty acids) that are correlated with these seasonal colony changes are limited in commercial diets and the environment. Experiment 2 tests the hypothesis that diets containing a better balance of these limiting nutrients can be used during these seasonal transitions to maximize colony health. The researchers are designing custom diets with high or low levels of these focal nutrients for use in Experiment 2, which begins in late ficscal year 2022 to early fiscal year 2023.
4. Canola (Brassica sp.) pollen fatty acids vary genetically and do not correlate with seed fatty acids. ARS researchers in Tucson, Arizona, collected fatty acid data research data that indicates that pollen fatty acid content varies among canola cultivars. Interestingly, the genetic variation in pollen fatty acid content did not correlate to seed fatty acid content, suggesting that selection on seed traits is independent of selection for pollen fatty acids. Based on these observations, canola breeders can develop cultivars with desirable seed traits that also produce pollen that is nutritious for bees. Additionally, similar Brassica species are used in almond orchards prior to bloom as important early season forage for colonies. High nutrient Brassica species can be incorporated into the seed mixtures that are currently planted in this region to increase pre-bloom colony nutrition.
5. Sunflower (Helianthus annuus) pollen fatty acids vary genetically and do not correlate with seed fatty acids. ARS researchers in Tucson, Arizona, discovered that both essential and non-essential fatty acids in pollen varied among commercial and wild type sunflower cultivars. Their research results showed that pollen fatty acid contents did not correlate with seed oil fatty acid contents, suggesting that intensive agronomic selection for seed oil fatty acids is independent of pollen fatty acid contents. As well, pollen fatty acid contents of the same cultivars, by and large, differed between field locations (Arizona and North Dakota), indicating that environmental conditions impact pollen fatty acid contents. This independence of seed and pollen fatty acid contents opens the possibility of selecting sunflower cultivars with nutritious pollen contents, likely dependent on local environmental conditions, that will be beneficial to bees without disrupting seed oil production for humans.
Review Publications
Meikle, W.G., Colin, T., Adamczyk Jr., J.J., Weiss, M., Barron, A. 2022. Traces of a neonicotinoid pesticide stimulate different honey bee colony activities, but do not increase colony size or longevity. Ecotoxicology and Environmental Safety. 231. Article 113202. https://doi.org/10.1016/j.ecoenv.2022.113202.
Kulyukin, V., Tkachenko, A., Price, K., Meikle, W.G., Weiss, M. 2022. Integration of scales and cameras in nondisruptive electronic beehive monitoring: On the within-day relationship of hive weight and traffic in honeybee (Apis mellifera) colonies in Langstroth hives in Tucson, Arizona, USA. Sensors. 22(13). Article 4824. https://doi.org/10.3390/s22134824.
Garber, K., Hoffman, G.D., Curry, R., Minucci, J., Dawson, D.E., Douglass, C., Milone, J., Purucker, S.T. 2022. Simulating the effects of pesticides on honey bee (Apis mellifera L.) colonies with BeePop+. Ecologies. 3(3):275-291. https://doi.org/10.3390/ecologies3030022.
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.
He, N., Zhang, Y., Duan, X., Li, J., Huang, W., Evans, J.D., Hoffman, G.D., Chen, Y., Huang, S. 2022. RNA interference-mediated knockdown of genes encoding spore wall proteins confers protection against Nosema ceranae infection in the European Honey Bee, Apis mellifera. Microorganisms. 9(3):505. https://doi.org/10.3390/microorganisms9030505.
Minucci, J.M., Curry, R., Hoffman, G.D., Douglass, C., Garber, K., Purucker, T.S. 2021. Inferring pesticide toxicity to honey bees from a field-based feeding study using a colony model and Bayesian inference. Ecological Applications. 31(8). Article e02442. https://doi.org/10.1002/eap.2442.
Messan, K., Rodriguez Messan, M., Chen, J., Hoffman, G.D., Kang, Y. 2020. Population dynamics of Varroa mite and honeybee: Effects of parasitism with age structure and seasonality. Ecological Modelling. 440. Article 109359. https://doi.org/10.1016/j.ecolmodel.2020.109359.
Carroll, M.J., Corby-Harris, V.L., Brown, N.J., Snyder, L.A., Reitz, D.C. 2022. Methoxyfenozide has minimal effects on replacement queens but may negatively affect sperm storage. Apidologie. 53. Article 33. https://doi.org/10.1007/s13592-022-00940-7.
Meikle, W.G., Barg, A., Weiss, M. 2022. Honey bees colonies maintain CO2 temperature regimes in spite of change in hive characteristics. Apidologie. 53. Article 51. https://doi.org/10.1007/s13592-022-00954-1.
Fisher, A., Cogley, T., Ozturk, C., Hoffman, G.D., Smith, B., Kaftanoglu, O., Fewell, J., Harrison, J. 2021. The active ingredients of a mitotoxic fungicide negatively affect pollen consumption and worker survival in laboratory-reared honey bees (Apis mellifera). Ecotoxicology and Environmental Safety. 226. Article 112841. https://doi.org/10.1016/j.ecoenv.2021.112841.
Chen, Y., Hoffman, G.D., Ratti, V., Kang, Y. 2021. Review on mathematical modeling of honeybee population dynamics. Mathematical Biosciences and Engineering (MBE) Journal. 18(6):9606-9650. https://doi.org/10.3934/mbe.2021471.
