Why a Treatment Schedule Matters
Varroa destructor is the single biggest threat to honey bee colonies worldwide. Without a consistent treatment plan, mite populations double roughly every 30 days during the active season. A colony that enters winter with more than 3 mites per 100 bees faces a very high chance of collapse before spring.
The key principle is simple: treat before the mite population explodes, not after. A scheduled approach — rather than reacting to visible damage — is the only way to keep varroa at safe levels year after year.
Monitoring First: Know Your Mite Load
Before any treatment decision, you need a baseline mite count. The two most reliable methods are:
- Alcohol wash: Collect approximately 300 bees (about half a cup) into a jar with 70% alcohol. Shake vigorously for 60 seconds, strain, and count mites. Divide mites by bee count and multiply by 100. Above 2% during the active season: treat immediately. Above 1% before winter: treat before clustering.
- Sugar roll: Same process but using powdered sugar instead of alcohol. Slightly less accurate but keeps the bees alive for return to the hive.
- Sticky board: Place a grease-coated board under the open-screen floor for 24 hours. Count mite drop. More than 10 mites per day in summer signals action needed.
Record every test result with the date and hive ID. Trends matter as much as individual readings.
Spring Treatment (March – April)
As colonies build up rapidly in spring, mite populations accelerate with them. Target this window when brood is still relatively limited, making oxalic acid vaporisation highly effective.
Oxalic acid vaporisation (OAV): 2.05g per hive. Repeat every 5 days for 3 treatments. Most effective when brood is minimal. Wear full respiratory protection — the vapour is damaging to lungs.
Treat only if your early spring wash shows above 1% infestation. Some colonies come through winter with manageable levels and need no spring intervention.
Summer Treatment (June – August)
Summer is the hardest season to treat because the hive is full of capped brood — where 70–80% of mites are hiding. Only treatments that penetrate capped cells are effective now.
Formic acid (MAQS or Formic Pro): Works through capped brood. Apply strips per product instructions. Effective down to 10°C. Do not apply above 29°C — it stresses the queen and increases drone brood mortality. Effective range: 10–29°C.
Thymol (ApiLife Var / Apiguard): Works at temperatures above 15°C. Place above the top bars. The vapour penetrates cells over 3–4 weeks. Highly effective but temperature-sensitive — do not use late in the season when temperatures drop.
Oxalic acid with a brood break: If you can cage the queen for 24 days (or perform a split), the colony temporarily goes broodless. Apply OAV twice during this window. This is the most effective summer approach — it combines brood break with treatment.
Late Summer / Pre-Winter Treatment (August – September)
This is the most critical treatment window of the year. The bees being raised now — the so-called "winter bees" — will carry the colony through until spring. Mites feeding on these bees shorten their lifespans and weaken the cluster. High mite loads now mean colony failure in February.
Oxalic acid dribble or vaporisation works well here as the colony is reducing brood naturally. Three OAV treatments 5 days apart after the last super is removed ensures no product residue in honey. Start as soon as honey supers come off — do not delay.
Target: below 0.5% mite load entering autumn.
Winter Treatment (November – January)
Winter is the only time the colony is truly broodless, making oxalic acid maximally effective. A single treatment during full broodlessness (confirmed by inspecting one hive — if truly broodless, apply to all colonies on the same day) kills 95%+ of mites with one application.
Apply OAV or dribble method in a dry period above 5°C. Avoid windy conditions. This winter treatment sets your colonies up for the strongest possible spring start.
Resistance Management
Rotating between chemical families prevents resistance. Do not use the same active ingredient more than twice in a row. Keep oxalic acid for broodless periods (winter + brood breaks), use formic or thymol as your main season-long treatments.
Log every treatment with start date, product, batch number, and result. Apps like SunnyBee store this automatically — when a vet inspection comes, your pharmaceutical record is already complete.