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Adult bee diseases

Winter losses

Severity : High November to March; discovered at the end of winterReview in progress
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Key points

  • Most winter losses are decided in August and September.
  • Varroa and viruses, starvation and queen failure are the three main causes.
  • A dead hive can be "read": cluster position, stores, heads in cells, varroa traces.
  • Close a dead hive quickly to prevent robbing and disease spread.

Losing colonies over winter is part of beekeeping, but high losses almost always have an identifiable cause. A large European study showed that disease control, especially of varroa, and beekeeper training strongly influence colony survival1.

Reading a dead hive

Varroa and viruses

  • Small cluster, often with the queen, and plenty of stores left.
  • Hive almost empty of dead bees.
  • White varroa droppings on the upper walls of brood cells; bees with deformed wings.

Starvation

  • Tight dead cluster, many bees head-first in the cells.
  • No stores in contact with the cluster; sometimes honey a few frames away (“isolation starvation” in hard frost).

Queen problems

  • No brood, or drone brood in worker cells (drone-laying queen or laying workers).

Nosema or dysentery

  • Combs and hive front heavily stained with faeces.
Photo needed — Dead hive opened at the end of winter: bees head-first in cells, combs without stores.

What to do straight away

  1. Close the entrance to stop neighbouring colonies robbing it.
  2. Check the brood: brood suspected of foulbrood must be reported.
  3. Remove the hive and only reuse the combs after checking them.

Preventing it next year

  • Treat for varroa right after the last harvest, then check.
  • Winter strong colonies; unite weak ones before autumn.
  • Check stores at the end of the season and in early spring.

From the field. The publisher of this site, a breeder in Normandy, feeds for winter case by case, colony by colony: up to three syrup feeds in September-October, checking stores until mid-October. Syrup stops when the clocks go back; after that, only fondant if needed, until the clocks go forward. Hefting the hive is not enough and can even mislead: look at the combs. And an early-summer dearth usually hits the finest colonies.

References

  1. Jacques A. et al. (2017). A pan-European epidemiological study reveals honey bee colony survival depends on beekeeper education and disease control. PLoS ONE 12(3): e0172591. doi.org
  2. FAO, IZSLT, Apimondia, CAAS (2021). Good beekeeping practices for sustainable apiculture. FAO Animal Production and Health Guidelines No. 25.

Updated : October 8, 2026
Written by : Apisanitas editorial team
Reviewed by : Review in progress