Location: Carl Hayden Bee Research Center
2020 Annual Report
Objectives
Honey bees obtain nutrients from pollen and nectar and are thus vulnerable in
landscapes with increased agrochemical exposure and decreased pollen diversity.
Agrochemical use has been increasing, but we do not yet have a comprehensive
understanding of the effects of acute and chronic exposure to these compounds on
colony health and survivorship. The objectives of this project are to evaluate
agrochemical exposure and nutritional stress with respect to bee nutrition, workerqueen interactions, pheromone profiles, queen retention, colony growth and forager activity. Published studies on pesticide exposure and the nutritional value of pollen and bee bread will help determine experimental treatments. The impact of the effects of pesticide exposure on the colony level will be evaluated by continuously monitoring hive weight, temperature and forager activity in row crop agriculture and in nut and fruit pollination. The role of nutrition on Varroa population growth and on colony recovery will also be examined.
Objective 1: Determine the nutritional composition of pollen before and after
conversion to bee bread and determine the effects of pesticide- and nutritionalstress on worker bees and on colony population growth and survival.
1A: Quantify the nutritional composition of pollen and bee bread according to the
time of year when the pollen is collected.
1B: Determine if worker hemolymph protein levels, hypopharyngeal gland development, and virus titers differ depending on pollen source, nutritional composition and time of year.
1C: Determine the effects of pollen contamination with fungicides and mite
treatments alone or in combination on worker hemolymph protein levels,
hypopharyngeal gland development, and virus titers.
1D: Examine the effects of exposure to pesticide-treated row crops on colony growth, nutritional status, phenology and foraging activity.
1E: Evaluate the effects of participation in commercial nut and fruit pollination on colony growth, activity and survivorship.
1F: Examine the effects of insect growth regulators (IGRs) on young adult
development and physiology.
Objective 2: Determine the effects of nutritional stress on Varroa parasitism
success and mite population growth in colonies.
2A: Evaluate the effects of nutrition and pollen source on Varroa reproductive
success and virus transmission.
2B: Assess the nutritional recovery time for colonies after infestation by Varroa.
Objective 3: Identify pesticide stress factors influencing worker-queen
interactions, pheromone production, queen supersedure, and successful queen
replacement.
3A: Evaluate the effects of neonicotinoid exposure on queen pheromone production,
queen supersedure and replacement, and worker-queen interactions.
3B: Evaluate the effects of neonicotinoid exposure on colony overwintering and
almond pollination.
3C: Monitor queen pheromone and ocimene production in colonies exposed to sublethal doses of the insect growth regulator methoxyfenozide.
3D: Monitor queen rearing, attractivenes, and ovary development in queens exposed to sublethal doses of pesticides.
Approach
Subobjective 1A: Determine whether pollens collected by bees in the spring and
summer differ in nutritional composition from pollens collected in the fall prior to overwintering. Pollen and bee bread will be collected from: 1) colonies foraging on undefined pollen sources and 2) colonies foraging on specific plants we provide.
Subobjective 1B: Evaluate the effects of pollen sources on worker and larval
hemolymph protein and lipids, on hypopharyngeal glands, and on virus and Nosema
levels in workers.
Subobjective 1C: Evaluate the effects of pollen with and without the fungicide
Pristine®, and with and without the miticide Amitraz, on colony health and worker
nutritional status during the active season.
Subobjective 1D: 1) Develop methods to link continuous weight and temperature data to hive phenology; and 2) conduct longitudinal and factorial field experiments to examine the effects of pesticide exposure and nutritional effects on changes in colony weight, internal temperature, forager activity and nutritional status.
Subobjective 1E: Examine the effects of participation in commercial pollination,
including agrochemical exposure, on bee colony growth and activity. Honey bee
colonies will be established, evaluated, and their weight and temperature monitored continuously prior to and during deployment to treated and untreated orchards.
Subobjective 1F: Examine the effects of field-relevant dosages of an insect growth regulator on bee hypopharyngeal glands and expression of genes involved in
ecdysteroid-induced gland degradation.
Subobjective 2A: Examine whether virus transmission is affected by the nutritional value of pollen and by bee nutritional stress by exposing bees to pollens of different nutritional value, and to artificial pollen dearth through the use of pollen traps, and monitoring varroa populations and virus incidence.
Subobjective 2B: Evaluate the effects of bee bread, made from pollens collected
during the active season, and of supplemental protein diet, on worker hemolymph
protein concentrations following parasitism by Varroa, in addition to field
experiments to examine colony recovery from Varroa infestation.
Subobjective 3A: Examine the effects of neonicotinoid exposure on pheromone-mediated interactions in bee colonies, with a focus on: Pheromone emissions of (E)-ßocimene, EO, BEP, QMP, and queen (E)-ß-ocimene, colony nutritional status, queen performance, forager effort, pesticide residues, and colony performance.
Subobjective 3B: Examine the effects of pesticide exposure on colony overwintering and almond pollination 1) during fall production of winter bees and 2) when colonies produce replacement bees for winter bees during the first annual forage by monitoring compounds listed in Subobj. 3A.
Subobjective 3C: Examine the effects of an insect growth regulator (IGR) on QMP and ocimene production in bee colonies offered different pesticide dosages in pollen and/ or syrup in controlled field studies.
Subobjective 3D: Examine the effects of an IGR on queen ovary development and
attractiveness by exposing larval queens to either contaminated wax or contaminated food and subsequently monitoring queen productivity.
Progress Report
This is the final report for bridging project 2022-21000-020-00D, ”Determining the Impacts of Pesticide- and Nutrition-Induced Stress on Honey Bee Colony Growth and Survival.” To learn more about the previous project, please see the FY19 final project report for 2022-21000-018-00D. This bridging project has been replaced by new project 2022-21000-022-00D, “The Honey Bee Microbiome in Health and Disease.”
Sub-objectives 1A, 1B, 1C, 1D, and 1F have been completed and the relevant data have been published. In support of Sub-objective 1E, research continued on evaluating the effects of sublethal concentrations of pesticides on bee colony growth and activity. Results of hive weight, thermoregulation and CO2 concentration from field experiments involving the exposure of honey bee colonies to field relevant concentrations of neonicoinoid pesticides have been submitted for publication. A field experiment was conducted with another pesticide that is related to neonicotinoids and that has been detected at high levels in honey and bee bread samples from commercial apiaries. That experiment was followed to its completion and data are being analyzed.
In support of Sub-objective 2B, the effects of nutrition on Varroa population sizes and virus levels in honey bee colonies were investigated in field experiments. We found that bees do not have a chance to recover from Varroa infestations because mites migrate into colonies in the fall and re-infest them. In our study, mite migration increased Varroa populations and virus levels so that they did not differ between colonies with and without optimized nutrition. A manuscript reporting the results of this study has been submitted and is in review.
Sub-objective 3A has been completed and the relevant data are being analyzed for publication. In support of Sub-objective 3B, a field experiment was repeated last fall for the second time to evaluate sublethal effects of the neonicotinoid imidacloprid on queen-worker interactions, queen pheromone signaling, and individual and colony performance in 60 overwintering colonies. The experiment was prematurely terminated by budgetary constraints caused by the backlog in agreements processing last summer. The experiment will be attempted for a fourth time at the end of FY20 through Spring FY21.
In support of Sub-objective 3C, a field experiment was performed last year to examine whether methoxyfenozide affects worker-queen interactions, queen pheromone signaling, and colony performance in overwintering colonies. The experiment was prematurely terminated by budgetary constraints caused by the backlog in agreements processing last summer. The experiment will be repeated again at the end of FY20 through Spring FY21.
For Sub-objective 3D, a field study was repeated for the third year to assess chronic effects of the Insect Growth Regulator methoxyfenozide on queen development, queen pheromone signaling, reproductive quality (ovary development and spermatheca sperm contents), and physiological quality (nutrient reserves of ovaries and non-reproductive tissues). Methoxyfenozide exposure during queen development did not affect queen survival and establishment (from larvae to mated, egg-laying queen) nor overall acceptance by colony workers. Data concerning effects on queen pheromone signaling, spermatheca sperm contents, ovary development and queen nutrient reserves are still being analyzed. This study demonstrates that methoxyfenozide may reduce the performance and longevity of queens exposed during queen development.
Accomplishments
1. Forage quality found to be more important to honey bee colonies than pesticide exposure in agricultural areas. Exposure of bee colonies to pesticide is a major concern to commercial beekeepers. However, the precision monitoring of bee colony behavior and growth, coupled with pesticide residue analysis, needed for a proper comparison is difficult for commercial operations to conduct. ARS researchers at Tucson, Arizona, ran two trials of 60 colonies each, monitoring colony strength and thermoregulation as well as pesticide residues, and found that while colonies in agricultural areas tend to have higher diversity and concentration of pesticide residues, those hives did as well or better than hives in areas with little or no commercial agriculture. This information helps beekeepers put the roles of different bee stressors in perspective.
2. Supplemental pollen feeding does not reduce Varroa populations or virus levels in honey bee colonies. Varroa mites are the major cause of colony losses worldwide because they parasitize honey bee larvae and adults, and transmit viruses. Beekeepers are interested in management practices to reduce the impact of Varroa because the mite migrates among colonies on foragers and is difficult to control. Feeding pollen to bees can stimulate immunity, so researchers at Tucson, Arizona, tested for differences in Varroa population growth and virus levels in colonies with and without supplemental pollen feeding. Mite populations and levels of Deformed Wing Virus rose throughout the season, were similar between fed and unfed colonies, and were correlated with the rate of mite migration into hives. Beekeepers can obtain some benefits from pollen feeding though, because it stimulated colony growth and improved colony survival.
Review Publications
Palmer-Young, E.C., Ngor, L., Nevarez, R.B., Rothman, J.A., Raffel, T.R., Mcfrederick, Q.S. 2019. Temperature dependence of parasitic infection and gut bacterial communities in bumble bees. Environmental Microbiology. 21(12):4706-4723. https://doi.org/10.1111/1462-2920.14805.
Hopper, K.R., Oppenheim, S.J., Kuhn, K.L., Lanier, K., Hoelmer, K.A., Heimpel, G.E., Meikle, W.G., O'Neil, R.J., Voegtlin, D.G., Wu, K., Woolley, J.B., Heraty, J.M. 2019. Counties not countries: Variation in host specificity among populations of an aphid parasitoid. Evolutionary Applications. 12(4):815-829. https://doi.org/10.1111/eva.12759.
Meikle, W.G., Weiss, M., Beren, E.D. 2020. Landscape factors influencing honey bee colony behavior in Southern California commercial apiaries. Nature Scientific Reports. 10:5013. https://doi.org/10.1038/s41598-020-61716-6.
Colin, T., Meikle, W.G., Wu, X., Barron, A. 2019. Traces of Imidacloprid induce precocious foraging and reduce foraging performances in honey bees. Environmental Science and Technology. 53(14):8252-8261. https://doi.org/10.1021/acs.est.9b02452.
Colin, T., Plath, J.A., Klein, S.K., Vine, P., Devaud, J., Lihoreau, M., Meikle, W.G., Barron, A. 2020. The miticide thymol in combination with trace levels of the neonicotinoid imidacloprid reduces visual learning performance in European honey bees (Apis mellifera). Apidologie. 51:499-509. https://doi.org/10.1007/s13592-020-00737-6.
Bandyopadhyay, R., Cardwell, K.F., Ortega-Beltran, A., Schulthess, F., Meikle, W.G., Setamou, M., Cotty, P.J. 2019. Identifying and managing plant health risks for key African crops: maize. In: Neuenschwander, P. and M. Tamò editors.Critical issues in plant health: 50 Years of Research in African Agriculture. Cambridge, UK: Burleigh Dodds Science Publishing, P. 173-212.
Corby-Harris, V.L., Deeter, M.E., Snyder, L.A., Meador, C.A., Gander, A.C., Hoffman, A.D. 2020. Octopamine mobilizes lipids from honey bee (Apis mellifera) hypopharyngeal glands. Journal of Experimental Biology. 223(8). https://doi.org/10.1242/jeb.216135.
Watkins de Jong, E.E., Hoffman, G.D., Chen, Y., Graham, R.H., Ziolkowski, N.F. 2019. Effects of diets containing different concentrations of pollen and pollen substitutes on physiology, Nosema burden, and virus titers in the honey bee (Apis mellifera L.). Apidologie. 50:845-858. https://doi.org/10.1007/s13592-019-00695-8.
Gage, S.L., Calle, S.N., Jacobson, N.N., Carroll, M.J., Hoffman, G.D. 2020. Pollen alters amino acid levels in the honey bee brain and this relationship changes with age and parasitic stress. Frontiers in Nutrition. 14. https://doi.org/10.3389/fnins.2020.00231.
