Chemical-Free Varroa Treatment That Reaches Capped Brood

Why beekeepers look for a chemical-free option

US beekeepers lost an estimated 39.9% of their managed colonies between April 2025 and April 2026, and varroa is a leading driver of those losses. The tools most of us rely on come with real limits:

• Resistance. Mites are developing resistance to the most commonly used miticides, so a product that worked once may work less well each season.
• Residues. Chemical treatments can leave residues in wax, honey and brood.
• Timing. Formic acid and thymol both restrict when you can treat relative to harvest, so the label can decide your schedule.
• Capped brood. Most of a colony’s mites are sealed under cappings, where contact treatments cannot reach them.

Read more about how varroa mites damage a colony.

How heat treatment works

Brood lives at 94 to 96°F (34 to 36°C). Mites start dying at 104°F (40°C). Worker bees tolerate about 118°F (48°C). Treatments sit in the gap, at 108 to 112°F (42 to 44°C).

Heat has killed varroa in peer-reviewed trials since 1991, and mites cannot evolve their way around it the way they do around a miticide. The hard part is holding the window. A colony fights the heat by fanning and evaporating moisture, and mites under cappings only die if the heat actually reaches them.

That is what ThermaHive is built to do. A wireless sensor between your brood frames reports every two seconds, and every heating decision is made against what the brood nest is experiencing. Heat rises from below through a diffuser board, and two fans move it up through the frames. Our best recorded hold averaged 112.03°F (44.5°C) against a 112°F (44°C) setpoint, with 99.6% of three hours inside ±2°F (±1.1°C). Delivery varies with the colony.

See how ThermaHive works, part by part.

What a treatment looks like

1. Install the Bottom Treatment Frame once. It stays on the hive and works as a screened bottom board the rest of the year.
2. Place the wireless sensors between your brood frames.
3. On treatment day, slide in the Heater Insert, set the Top Box on, and plug in.
4. Start it and walk away. We recommend 112°F (44°C) for three hours. Budget 30 to 60 minutes of preheat, so about three to four hours start to finish.

The hive stays closed. The heater shuts off at the end of the hold, and every session is logged to the SD card so you can see the curve it held.

How often to treat

We recommend 2 consecutive treatments, spaced 7 to 14 days apart, each brood cycle.

• Smaller colonies with low starting mite counts, or VSH stock, can often manage with 1 treatment per brood cycle.
• Large colonies may need up to 3 consecutive treatments to bring mite counts down.

Why spacing matters: mites sealed in capped brood during the first treatment emerge within the next 1 to 2 weeks, and the follow-up treatment catches them.

Wash before, then again afterward, and let your counts guide you. Our free checklist walks you through it.

What the 2026 field season showed

We logged 69 treatments across four apiaries from April to September 2026 and published the full record, including the washes that came back higher.

• 51% average reduction per treatment across 49 paired mite washes on 16 colonies (95% CI 31 to 65%). This is the number to plan around.
• 84% reduction from season peak at our West River research apiary, across 6 colonies. Results vary.
• No ThermaHive-treated colony was lost (20 hives), against one of six in the chemical control group.

Heat is not the strongest single dose on the market: amitraz strips are estimated at about 95% per application. The case for heat is that you can repeat it on your own schedule, with no resistance, residue or harvest restriction. Read the full 2026 results or compare heat with chemical treatments.

Honey, wax and your harvest

Nothing is applied to the hive, so nothing is left behind and there is no waiting period before harvest. Treatments run far below the melting point of beeswax, around 140 to 150°F (60 to 66°C). You may find wax slightly softer afterward.

Heat rises into a super, but a super runs several degrees cooler than the brood nest, so mites up there get a weaker dose. Keep a queen excluder in place, or treat with the super configured as a brood box.

Treating more than one hive

Only the Bottom Treatment Frame stays on each hive. The Heater Insert and Top Box move with you, so each extra hive needs a Bottom Box Frame, from $81.38, rather than another full kit.