How should bees be treated for mites in winter? - briefly
Apply a licensed miticide such as oxalic‑acid vapor or formic‑acid dribble during the cold period when brood is minimal, ensuring correct dosage and adequate ventilation. Conduct a post‑treatment inspection in early spring to verify mite reduction and colony health.
How should bees be treated for mites in winter? - in detail
Winter management of varroa mites requires a combination of chemical, mechanical, and environmental strategies that maintain colony health while limiting parasite reproduction.
Effective chemical control relies on licensed miticides applied during the fall brood‑break period. Products such as oxalic acid, administered by vaporisation or syrup feeding, penetrate the colony when brood is absent, exposing the mites that reside on adult bees. Formic acid treatments, delivered through impregnated pads, continue to affect mites throughout the winter months, provided temperature remains within the recommended range (10–25 °C). Dose calculations must follow label instructions to avoid toxic effects on bees.
Mechanical interventions focus on reducing mite numbers without chemicals. A thorough inspection before winter onset allows removal of heavily infested frames. Re‑queening with a mite‑free queen reduces the likelihood of reinfestation, as new queens are less likely to carry varroa. Splitting strong colonies into smaller nucs creates a brood‑less interval that interrupts the mite life cycle.
Environmental control enhances the efficacy of other methods. Maintaining hive temperature above the lower threshold for formic acid activity (approximately 10 °C) ensures continuous mite mortality. Reducing hive humidity to 50–60 % limits mite survival on adult bees. Proper ventilation prevents condensation, which can weaken bees and increase susceptibility to parasites.
A recommended winter protocol:
- Conduct a pre‑winter varroa count using a powdered sugar roll or alcohol wash.
- If infestation exceeds 3 % of the adult population, apply a fall oxalic acid vaporisation treatment.
- Initiate a brood‑break by removing all capped brood frames for at least three weeks.
- During the brood‑less period, treat with a second oxalic acid application or a formic acid pad, respecting temperature limits.
- Re‑introduce brood frames gradually as temperatures rise, monitoring mite levels monthly.
- Replace the queen with a mite‑free individual before the colony enters full winter dormancy.
Record-keeping of treatment dates, dosages, and mite counts supports long‑term colony health assessment. Combining these practices minimizes varroa pressure throughout winter, preserving colony strength for the spring nectar flow.