Project : USDA ARS

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Research Project: Managing Honey Bees Against Disease and Colony Stress

Location: Bee Research Laboratory

2024 Annual Report

Objectives
The overarching goal of the project is to develop management strategies for bee diseases & colony health & to provide the beekeeping community with advice for best practices to build & maintain healthy bee populations for pollination. This goal will be achieved by pursuring the following specific objectives: OBJ 1: Develop diagnostic & data management tools for use in mitigating the effects of current & emerging honey bee diseases & pests & continue to operate the Agency’s Bee Disease Diagnostic Service. [NP305, Component 2, PS 2A & 2B] 1.A: Identify & characterize new & emerging pathogens that cause honey bee diseases & to develop efficient diagnostic markers to monitor disease onset & progression in honey colonies; 1.B: Develop diagnostic method for measuring stress in honey bees; 1.C: Improve diagnostic & informatic tools for bee health. OBJ 2: Develop novel & effective treatment solutions, including varroacides & natural products, that reduce the incidence & prevalence of bee diseases & disorders to help beekeepers maximize pollination services & honey production. [NP305, Component 2, PS 2A & 2B] 2.A: Develop tools & strategies for preventing & controlling honey bee pests that harm individual bees & damage hive products; 2.B: Develop RNAi based specific therapeutics for bee diseases; 2.C: Identify natural products that reduce bee diseases; 2.D: Develop novel methods to mitigate the detrimental effects associated with pesticide exposure. OBJ 3: Analyze the seasonal behavior & physiology of adult worker bees, & thus develop improved best management strategies for increasing the overwintering success of honey bee colonies in the field. [NP305, Component 2, PS 2A & 2B] 3.A: Refine our understanding of the seasonality of honey bee colonies & identify abiotic & biotic factors that disrupt the timing or occurrence of seasonal events; 3.B: Determine overwintering strategies of honey bee pests, including Varroa mites, wax moths, & small hive beetles, & develop methods & tools for their control; 3.C: Determine the effects to biological clock/seasonal physiology of honey bees from different overwintering strategies employed by beekeepers & develop successful overwintering strategies. OBJ 4: Determine the causes of queen failures & improve honey bee queen quality related to colony survivorship. [NP305, Component 2, PS 2A & 2B] 4.A: Improving queen genetic diversity & their resistance to diseases; 4.B: Compare available queen lines & stocks to determine their disease Resistance; 4.C: Define the epigenetic factors of queen fitness & develop strategies to improve queen quality. OBJ 5: Analyze the interactions between honey bee nutrition, their microbiomes, chemical stress, disease, & hive treatments, to improve bee health & performance. [NP305, Component 2, PS 2A & 2B] 5.A: Determine the effect of nutritional supplementation on honey bee behavioral development & disease immunity; 5.B: Determine the relationship between gut microbiota & nutrition on honey bee behavior & immunity to diseases & abiotic stressors; 5.C: Improve bee defenses in the face of abiotic & biotic stress.

Approach
Bee Research Laboratory scientists combine laboratory and field approaches and integrate physiology, molecular biology, toxicology, ecology, and multi-omics technologies (genome, metagenome, transcriptome, epigenome, metabolome, and microbiome) into an interdisciplinary research program to generate new knowledge, technologies, and tools for 1) diagnosing, treating, and mitigating bee diseases and pests, 2) creating platforms that provide data sources and analytic applications to advance bee research and to broaden the range of our custom services, 3) improving colonies' overwintering success, 4) developing strategies for improving queen quality, and 5) discovering nutrition-based approaches for disease prevention and health promotion and protecting bees from pesticides and other toxins present in the environment. BRL scientists work with industry leaders and stakeholders to help license and develop products that will be useful for beekeepers and customers.

Progress Report
Progress was made on all Objectives, which fall under NP305 (Crop Production), Action Plan Component II (Bees and Pollination), and Problem Area A (Honey bees). During this period, the Bee Disease Diagnostic Service responded to field colony losses by identifying disease-causing agents in bee samples sent by beekeepers and inspectors across the U.S. These determinations included over 50 positive identifications of American foulbrood, helping in the control of this regulated infectious disease. Researchers also analyzed and published 40 years of diagnostic data for Varroa mites, nosema disease and brood diseases, providing the largest available long term baseline for honey bee disease trends. ARS researchers in Beltsville, Maryland, produced breakthroughs in disease diagnostics, the identification of colony health stressors, and management strategies for overwintering of honey bee colonies, a persistent challenge for the industry. They also vetted and patented a novel antiviral treatment based on natural products and carried out field trials with a novel compound to control Varroa mite parasites. These efforts are directed at handing off both candidates to the beekeeping industry for use in the field. Progress towards AI-informed small molecules identified two antiviral compounds that are now candidates for field trials with industry support. Researchers also described mechanisms of honey bee immune defenses and showed how nutrition and disease shape longevity and disease susceptibility. Genetic analyses of current honey bee populations showed variation across states in different genetic lineages, helping breeding researchers determine the suitability of localized breeding programs. Research on mite-vectored viruses helped identify the risk factors for colonies across the season when mite vectors are present, showing more precisely how often these vectors move from bee to bee. These insights will direct recommendations for the optimal time to treat for mite parasites, and also indicate the urgent need for antiviral controls. Collectively, research under this program tackled the long term goal of managing honey bees against disease and colony stresses, by identifying key causes of colony losses and developing medicines and management tools to help reduce those losses. These efforts were funded by base funds, interagency transfers, stakeholder grants and governmental grants.

Accomplishments
1. Improved diagnostics and identified the causes of bee declines. Beekeepers face annual losses of nearly 50% of existing colonies, impacting their abilities to provide pollination for high-value crops. ARS Researchers in Beltsville, Maryland, conducted in-depth studies of commercial apiaries with healthy or declining colonies, generating economic data and identifying causes of disease. They also cured, analyzed and published decades of data (1984-2022) from the Honey Bee Disease Diagnostic Service to identify trends and causes of colony mortality. This effort showed the connections between climate regions and disease intensities in various U.S. states. They have identified no increasing resistance to antibiotics used to treat brood diseases in the U.S. and a major transition in the main bacterial threats. This has led to management suggestions and predictive measures for beekeepers and regulators can use to decrease costs and improve the reliability of a critical U.S. pollinator.

2. Developed novel controls for mite disease in honey bees. Varroa mites have been identified as the single most important cause of honey bee colony losses, costing beekeepers millions of dollars in management expenses and colony replacement costs. Lost productivity due to these mites puts honey bees, the primary agricultural pollinator, at risk and imperils over $20 billion in U.S. agricultural output. ARS researchers in Beltsville, Maryland, have tested numerous candidates for the chemical control of Varroa mites resulting in 40 compounds screened in the lab, and three in the field. Experiments over the last two years have identified two promising candidates. A histological atlas of Varroa internal anatomy is being used to help understand the affected target site(s) in Varroa of the aforementioned compound. Additionally cues used by Varroa to locate host larvae, have been identified, which provides another potential control route. Finally, ARS researchers have documented the means by which viruses move within honey bee colonies, showing the key roles played by Varroa mites and bee-to-bee transmission. The research quantified the movement of viruses from bee to bee even following the control of mite numbers. These insights will lead to management changes directed at minimizing bee losses, decreasing costs of beekeepers and crop pollination and ensuring food security for high-value fruit, nut, and vegetable crops.

3. Improved stress management to reduce honey bee losses. Beekeepers need new tools to decrease honey bee colony loss rates and improve productivity. Challenges to honey bee health arise from disease agents, chemical stress and nutritional challenges. Better pollen nutrition was shown to decrease viruses and improve worker bee survival and foraging behavior. Bees are especially stressed in the winter months due to temperature, parasites, and the inability to replace an aging workforce. ARS Researchers in Beltsville, Maryland, discovered a key honey bee cell signaling pathway, and then used a therapeutic strategy to target this pathway, improving bee and colony survivorship. They also showed how bees are differently susceptible to chemical stress in winter, improving survivorship management options. Finally, they deployed food-safe alternatives including cyclodextrins and natural plant compounds to increase worker bee survival in the face of stress and disease. This work was coupled with a nationwide analysis of honey bee varieties, setting the stage for understanding climate-based preferences of honey bee stock. This groundbreaking work not only enhances the vitality of the beekeeping industry but also supports agricultural food production by ensuring healthier bee populations. The results should translate into lower production costs for beekeepers and lower pollination expenses for a $20B high-value crop industry.

U.S. DEPARTMENT OF AGRICULTURE

Bee Research Laboratory: Beltsville, MD