Winter colony losses are one of the most demoralising experiences in beekeeping. The hard truth is that most winter losses are preventable, and most of the work that prevents them happens in September and October, not December.
Why fall preparation matters so much
A colony's winter survival depends on three factors: the health and number of winter bees, adequate food stores, and low Varroa levels. All three are directly determined by what you do in the final 6–8 weeks of the active season.
Winter bees are physiologically distinct from summer bees — raised in September and October, they live 4–6 months rather than the 6 weeks typical of summer bees. They are the colony's bridge to spring. Winter bees raised under high Varroa pressure are compromised — their fat bodies are smaller, their immune function is reduced, and their lifespans are dramatically shortened.
Late August: Varroa assessment and treatment
Do a varroa alcohol wash now. This is the most time-sensitive item on the list. If mite levels are at or above 1–2 mites per 100 bees, treat immediately.
For late-summer treatment, choose based on temperature:
- Above 60°F consistently: Thymol (Apiguard or ApiLifeVar) — two full treatment cycles, 2 weeks apart. Pull honey supers before applying.
- Below 60°F or variable: Oxalic acid vapour, 3–5 applications every 4–5 days.
- High mite levels needing rapid knockdown: Formic acid (MAQS).
Do a follow-up alcohol wash 2 weeks after the last application to confirm efficacy.
Early September: Food assessment and supplemental feeding
Assess stores by hefting. A colony needs 60–80 pounds of honey going into winter. Each fully capped medium frame holds about 4–5 pounds; each deep frame about 6–8 pounds.
Feed with 2:1 sugar syrup (2 parts sugar, 1 part water by weight) in early fall — higher concentration helps bees ripen and cap the syrup faster as temperatures drop. Do not use 1:1 syrup in fall.
Use an internal feeder — robbing pressure is high as nectar dries up, and entrance feeders attract robbers.
Mid-September: Final brood check and queen assessment
Do your last full inspection of the season. Look for: a laying queen with a solid brood pattern (if absent or failing, this is your last practical opportunity to requeen), adequate brood (solid patch of capped brood means a strong cohort of young bees emerging in October), no disease signs, and space configuration (consolidate to fewer boxes if population is declining).
Reduce the entrance to 3–4 inches to help guard bees defend against robbing and, later, against mice.
Late September to early October: Physical winterisation
Mouse guards: Install by early October at the latest. A mouse that gets into a hive in October can cause catastrophic damage to a wintering colony.
Ventilation: Moisture is a greater killer of Pacific Northwest colonies than cold. Ensure:
- A screened bottom board (left open)
- An upper entrance (1-inch notch in inner cover) to allow warm, moist air to escape
- A moisture quilt box above the inner cover to absorb condensation
Wind protection: Stack straw bales around the windward side or wrap in roofing felt. Leave ventilation points open.
Secure the lid with a rock, strap, or weight — Pacific Northwest storms can be fierce.
Hive stand: Ensure a slight forward tilt so water drains out the entrance.
October: Final checks before winter
One last heft. If stores feel light, emergency feeding with fondant (sugar candy) or dry sugar applied above the inner cover can be added even when temperatures are too cold for syrup.
Emergency candy recipe: Heat 2 cups water and 5 pounds sugar to 240°F (soft ball stage), pour into a mold lined with parchment, allow to cool. Place above the cluster as needed.
Stop opening the hive once temperatures drop consistently below 50°F. Every cold inspection chills the cluster, and there's little useful information worth the cost. Trust your preparation.
A winter check without opening
On a mild winter day (above 50°F), listen at the entrance — a gentle hum means the cluster is alive. Check for dead bees being removed (healthy hygienic behaviour). If concerned about stores, briefly lift the outer cover to check. Slide a candy board in above the cluster if stores look thin, close quickly, and leave them alone.
Everything good that happens in spring traces back to what you did in September and October.
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