Winterizing Hives With Varroa Management Built In

Fall is the most consequential time of year for varroa management in northern climates. The bees you raise in August and September are the bees that will carry the colony through winter. If those bees are raised while mite loads are high, they will be virus-damaged, shorter-lived, and unable to form a healthy winter cluster. Getting varroa under control before the winter bees are raised is the single most important thing you can do for your colonies' survival.

Understanding the Winter Bee Connection

Winter bees are physiologically different from summer bees. They have enlarged fat bodies, live four to six times longer than summer bees, and serve as the protein reserves the colony draws on to raise spring brood. These bees are raised in late summer and early fall, roughly August through October depending on your latitude.

Varroa mites feeding on developing pupae inject viruses, particularly Deformed Wing Virus (DWV), that compromise fat body development and shorten bee lifespan. If your mite population peaks in August while winter bees are being raised, the damage is done before you ever see the fall symptoms. The colony heads into winter with compromised bees. It may still look reasonable in October but collapses between December and February.

The solution is to have mite levels under control before the winter bee-raising window opens. In the northern US, this means treating no later than mid to late August in most regions.

Fall Varroa Treatment Options

Apivar (amitraz strips) is the most common fall treatment. Strips go in after the last honey super is off and stay in for the full 6 to 8 week duration. Apivar is not temperature sensitive within normal fall ranges, which makes it reliable. For fall use, place strips in August and remove them by mid-October to early November depending on your climate.

OAV during natural broodless period. In the northern US, colonies typically become broodless by December through January as temperatures drop consistently below 50 degrees Fahrenheit. This natural broodless period is an opportunity to use oxalic acid vaporization with maximum effectiveness, since all mites are phoretic. Three treatments five days apart during confirmed broodlessness can reduce mite loads to near zero. The timing varies by year and latitude. Do not rely on calendar date alone. Verify broodlessness by inspecting before treating.

Sequential treatment. Many beekeepers use Apivar in August to knock down summer mite loads, let the strips run their full course, and follow with OAV during the December-January broodless period as a final cleanup. This two-step approach is highly effective and reduces the chance of heading into spring with residual mite pressure.

Confirming Treatment Success Before Winter

Treatment is not complete without verification. Do a mite count after your fall Apivar course finishes. An acceptable post-treatment count in fall is below 1% (1 mite per 100 bees). If you are still above 2% after a full Apivar course, the product may have been applied late, may not have been given enough time, or you may be dealing with amitraz resistance. In that case, follow with OAV or switch to a different mode of action.

Log your pre-treatment and post-treatment counts. This data tells you how well the treatment worked, flags hives with potential resistance, and gives you a starting point for spring monitoring.

Physical Winterization After Varroa Treatment

Once your varroa work is done, physical winterization follows. The order matters: complete varroa treatment first, then prepare for winter. Treating in November when brood is already sparse is less effective and may not protect winter bees that were already raised during the high-mite window.

Physical winterization checklist:

• Confirm adequate stores. Sixty to 80 pounds of honey for a northern winter, which is roughly 8 to 10 full deep frames or equivalent. Feed fondant or candy boards if stores are short.
• Reduce the entrance to deter robbing and mice. A mouse guard over the entrance works well.
• Ensure ventilation. Some moisture escaping from the hive is important. Top ventilation through a notch in the inner cover or a moisture quilt prevents condensation from dripping on the cluster.
• Remove or secure empty supers. They add unnecessary insulation problems and give mice extra harborage.

Tracking Your Winterization Protocol

Colonies that survive winter well typically had low mite counts going into fall, strong populations of healthy winter bees, and adequate stores. Colonies that die over winter often had high mite counts in August regardless of how well they were treated in October.

VarroaVault lets you log your fall mite counts, treatment dates and products, and post-treatment verification counts, giving you a complete record of each colony's winterization status. When you open hives in spring, you can correlate winter survival or losses against the fall data and refine your protocol for the following year. See the treatment threshold alerts feature for setting up reminders to count and treat during the critical August window.