Location: Bee Research Laboratory
Project Number: 8042-30500-002-044-I
Project Type: Interagency Reimbursable Agreement
Start Date: Sep 29, 2026
End Date: Sep 30, 2027
Objective:
Honey bees play a pivotal role in the success and sustainability of U.S. agriculture. As the primary managed pollinators in agricultural production systems, they are essential not only to the production of approximately one-third of the food consumed in the United States, including fruits, nuts, vegetables, and oilseeds, but also to the pollination of crops that provide forage for livestock. This indispensable agricultural resource is increasingly threatened by disease, parasitic mites, pesticide exposure, and other environmental stressors. Pesticide exposure is an important threat to honey bee health because lethal and sublethal effects can impair survival, behavior, foraging, development, and colony function. Parasite pressure and pesticide exposure may also act together to reduce colony resilience and increase the risk of colony loss. Research that prevents, mitigates, and more accurately characterizes these stressors is therefore directly relevant to agricultural productivity. The Agriculture Improvement Act of 2018 authorized the use of Commodity Credit Corporation (CCC) funds for the Emergency Assistance for Livestock, Honeybees, and Farm-Raised Fish Program (ELAP). ELAP, administered by USDA's Farm Service Agency (FSA), provides financial assistance to US beekeepers for qualifying colony losses associated with eligible causes of loss. This project supports the honey bee component of ELAP by addressing two interacting categories of colony-loss pressure: biotic stress from parasitic mites and abiotic stress associated with pesticide exposure. The research will develop tools to prevent or reduce colony injury and evaluate protective interventions, toward the goals of:
• Reducing the frequency or severity of colony losses that may generate producer need for ELAP assistance.
• Provide APHIS, ARS, FSA, and industry stakeholders with research products that support prevention, preparedness, and technically informed program implementation.
The proposed project consists of five inter-related objectives:
1. Define the molecular responses of Varroa destructor to falcarinol, a novel miticide, nacross control, hormetic, and acaricidal exposure ranges.
2. Optimize and validate Stratiolaelaps scimitus as a practical surrogate for early-stage screening of candidate miticides intended for Varroa and Tropilaelaps mites.
3. Establish intermediate, frame-scale assays that measure efficacy against reproductive-stage mites while detecting adverse effects on brood development, queen function, and worker social behavior.
4. Identify and validate brood-associated chemical cues that attract, repel, excite, arrest, or otherwise disrupt Varroa mites during acquisition of capping-stage brood hosts.
5. Determine whether falcarindiol and selected cyclodextrins reduce adverse effects of pesticide exposure in adult honey bees under controlled laboratory conditions.
Approach:
Early screening and mode-of-action studies identify promising tools; intermediate assays evaluate effects on mites, individual bees, and essential social functions; and the strongest candidates advance toward colony-level validation.
Obj. 1: Key activities
• Expose Varroa mites in standardized vial bioassays to a negative control, approximately 40 µg/mL falcarinol, and an efficacious range of approximately 400–800 µg/mL, with appropriate biological and technical replication.
• Collect surviving mites at a standardized post-exposure time, preserve samples, extract total RNA, and prepare cDNA libraries using validated procedures.
• Generate paired-end RNA-sequencing data and perform quality control, genome alignment, transcript quantification, and differential-expression analysis.
• Identify dose-responsive genes and enriched pathways, with particular attention to detoxification, oxidative-stress, signaling, neural, and cuticle-related processes.
Obj. 2: Key activities
• Optimize rearing, feeding, temperature, humidity, handling, and exposure conditions that support reproducible Stratiolaelaps survival under hive-relevant conditions.
• Develop separate contact and volatile-exposure assay formats.
• Establish dose-response benchmarks using conventional miticides, including thymol, formic acid, and oxalic acid.
• Compare relative sensitivity and rank-order responses among Stratiolaelaps and Varroa.
• Define criteria for when a candidate should advance from surrogate screening to target-mite confirmation.
Obj. 3: Key activities
• Test selected chemical and semiochemical candidates across relevant doses, formulations, and exposure durations in controlled observation-frame systems.
• Quantify mite invasion of brood cells, mite reproduction and emergence, brood-cell capping, adult bee emergence, overall brood-rearing rates, and infestation levels.
• Measure queen oviposition and worker retinue behavior using direct observations and video-based behavioral analysis.
• Integrate mite efficacy and bee-safety endpoints to identify treatment windows and formulations suitable for whole-colony evaluation.
Obj. 4: Key activities
• Use existing volatile profiles of eggs, larvae, capped brood, and the capping environment to nominate candidate odorants and mixtures.
• Prioritize compounds that produce Varroa electrophysiological responses and evaluate them in choice and no-choice behavioral assays.
• Characterize responses of both host-isolated mites and phoretic mites attached to adult workers using video-tracking analysis.
• Compare single compounds with biologically relevant mixtures and profiles from host versus non-host brood stages.
• Formulate promising candidates and assess activity in progressively more complex, hive-relevant environments.
Obj. 5: Key activities
• Establish a reproducible pesticide-stress model using one or more APHIS/ARS-prioritized pesticides, exposure routes, and sublethal dose ranges.
• Use a factorial design that includes, at minimum, an untreated control, pesticide-only control, each candidate intervention alone, and pesticide plus each candidate intervention; include vehicle controls and suitable concentration ranges.