EJbees East Jefferson Bee Club

By Ron Lynn Varroa mites (Varroa destructor) remain the most serious threat to managed honey bee colonies. These mites weaken bees directly and spread viruses that can lead to colony collapse if left untreated. In 2025, the U.S. Environmental Protection Agency (EPA) approved a new active ingredient for varroa control called Vadescana. It introduces a novel approach to mite management for honey bee colonies. What Is Vadescana? Vadescana is a double-stranded RNA (dsRNA) active ingredient designed specifically to control varroa mites. It works through a natural biological process called RNA interference (RNAi), which blocks the production of a protein that the mite needs to survive and reproduce. In its final registration decision, the EPA states: “The effects of Vadescana are highly specific to Varroa mites. It does not affect humans or other non-target organisms, including bees and threatened or endangered species.” — U.S. Environmental Protection Agency, Final Registration Decision (2025) Because the RNA sequence targets a gene unique to varroa mites, EPA concluded that Vadescana does not affect honey bees or other non-target organisms when products containing it are used according to the label. How Does It Work in the Hive? Unlike traditional miticides that rely on chemical toxicity, RNAi works by disrupting gene expression inside the mite. When varroa mites encounter the dsRNA in the hive, their ability to reproduce is impaired, which slows population growth and helps keep mite levels below damaging thresholds. The first commercial product using Vadescana is Norroa, which is applied inside the hive following label directions. As with all treatments, timing and monitoring are critical for success. Why This Matters to Beekeepers · New mode of action: Vadescana represents a completely different approach than organic acids, essential oils, or synthetic miticides, making it valuable for treatment rotation. · Targeted control: Designed specifically for varroa mites, which reduces risks to bees and beekeepers. No PPE required. · Fits IPM practices: Intended to be used alongside monitoring, record-keeping, and integrated pest management strategies. Important Reminders · Vadescana-based products are not a substitute for mite monitoring. Regular testing (alcohol wash or sugar roll) remains essential. · Always follow the product label and check state registration requirements. · Rotating treatments remains one of the best tools to reduce the risk of mite resistance. Quick FAQs Is this safe for bees? Yes. The EPA states: “The effects of Vadescana are highly specific to Varroa mites. It does not affect humans or other non-target organisms, including bees and threatened or endangered species.” Is this the same as mRNA vaccines? No. While both involve RNA, RNA interference (RNAi) works by silencing specific mite genes. It does not trigger an immune response and does not alter bee biology. Is it a GMO? No. Vadescana does not modify the genetics of bees, mites, honey, or wax. The RNA breaks down naturally over time. Is it safe for honey and wax? Yes. EPA has established an exemption from the requirement of a tolerance for residues of Vadescana double-stranded RNA in or on honey and honeycomb when the product is used according to the label. (This means no maximum residue level is required because EPA determined it does not pose a dietary risk.) Can this replace other varroa treatments? No. Vadescana is best used as part of an Integrated Pest Management (IPM) approach that includes monitoring mite levels and rotating treatments. Resources & Further Reading · American Bee Journal, January 2026, p. 51 Vadescana: Using Synthetic Biology to Control Varroa — Bill Hesbach · EPA: New Tool to Protect Honey Bees from Varroa Mites https://www.epa.gov/pesticides/epa-provides-new-tool-protect-honey-bees-ensuring-safe-and-abundant-food-supply · EPA: Registered Products for Varroa Mite Control https://www.epa.gov/pollinator-protection/epa-registered-pesticide-products-approved-use-against-varroa-mites-bee-hives · GreenLight Biosciences: RNA-Based Varroa Control (Norroa) https://www.greenlightbiosciences.com/articles/greenlight-biosciences-launches-norroa-the-first-rna-based-treatment-for-varroa-mites · How Does Norroa Stop Mites Before They Even Grow? Q&A (video) — Mann Lake Bee Supply https://www.youtube.com/watch?v=FyMYbO2R81E · Peer-reviewed research on RNAi and Vadescana (Pest Management Science, 2024) https://pubmed.ncbi.nlm.nih.gov/38801186

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