Winterizing Your Bee Colonies

Getting your bee colonies ready for winter

Autumn is when it's decided whether your colonies will come through the winter healthy. If you take the right steps at the right time, you'll cut winter losses considerably – they can never be ruled out entirely – and you'll go into the new season strong.

The right time

Winter preparation begins after the last harvest – usually late July to mid-August. From then on, the honey stays in the colony. The bees start rearing winter bees: long-lived individuals with special fat bodies that can live for up to 6 months.

Varroa treatment in late summer and winter

The most important step: after the last harvest, an effective varroa treatment must take place. Without an effective treatment, too many mites survive and damage the freshly reared winter bees.

Proven methods:

• Oxalic acid trickling once broodless, in December/January (most effective)
• Oxalic acid vaporizing likewise only in a broodless colony – oxalic acid does not reach mites under capped brood; use only preparations approved for it
• Formic acid in August after the last honey harvest – according to the Celle bee institute at 15–25 °C, above 25 °C only in the evening; wear protective gloves, do not inhale the vapours (BVL)

Feeding

A colony needs about 15–20 kg of food for the winter. If honey was taken, the food must be replaced.

• Sugar water 2:1 (2 kg sugar to 1 L water) in large feed troughs
• Finish by mid-September – the bees need time to evaporate the water
• Check the amount of food and top up if needed

Mouse guards & winterizing

A mouse guard with an 8 mm mesh in front of the entrance protects the colony – bees fit through easily, mice don't.

Reduce the entrance size to 5 cm in winter. Less draft, less robbing.

Check colony strength: at least 5–6 combs covered with bees. Weak colonies survive the winter poorly. Uniting two weak colonies is better than losing both.

Ventilation instead of warmth

Damp air is more dangerous than cold. Mesh floors (open or lightly restricted) help. Don't put a sheet of plastic over the boxes – condensation promotes mold and nosema.

Respect the winter rest

Don't open the hive as long as temperatures stay below 10 °C. The winter cluster breaks apart and can no longer warm itself properly. Only intervene briefly in an absolute emergency (risk of starvation) – place feeding paste or fondant directly on top.

Tip: Give the hive a gentle knock in winter. A deep, calm hum means everything is fine. Silence or a frantic rustling sound can indicate problems.

Sources

• LAVES – Institute for Apiculture Celle: Varroa-Sommerbehandlung (Bieneninstitut Celle informiert Nr. 62), as of Jul 2013, accessed 5 Oct 2026
• Federal Office of Consumer Protection and Food Safety (BVL): Standardzulassung Ameisensäure 60 % ad us. vet. (2469.99.99), accessed 5 Oct 2026
• Bavarian State Institute for Viticulture and Horticulture (LWG), Institute for Bee Research: Träufelbehandlung mit Oxalsäure, accessed 5 Oct 2026

The sources support individual statements in this article. The organisations named have neither reviewed nor endorsed it.