European Foulbrood: Recognising It Early

European foulbrood is a notifiable disease across most of Europe, and it is the one most often missed by careful beekeepers — not because it is hard to see, but because the early frame looks like ordinary spring patchiness in a colony that is still growing.

The bacterium, Melissococcus plutonius, competes with the larva for food in the gut. Larvae die before capping, usually at four or five days old, in a colony under nutritional or handling stress. That timing is the key to spotting it.

What You Actually See

Work through a suspect frame slowly, in good light, holding it so the sun falls into the cells.

Two of those matter most: twisted larvae and death before capping. A frame with pearly, correctly coiled larvae and a patchy sealed pattern is far more likely to be a failing queen or chilled brood.

Ruling Out AFB

American foulbrood kills after capping, leaves sunken, greasy, perforated cappings, and produces a remains that ropes out 20 mm or more on a matchstick. EFB remains are watery and break. The rope test is worth doing on any suspicious frame — it takes ten seconds and it is the difference between a treatable problem and a burn order.

Neither test is a diagnosis. Both diseases are notifiable in Belgium, the Netherlands, and most of the EU: if you suspect either, stop inspecting, close the hive, and contact your regional bee inspector or veterinary service. Lateral-flow field kits are useful for triage but are not a legal diagnosis, and false negatives are common at low infection levels.

Why It Appears When It Does

EFB follows stress rather than causing it. The usual triggers in a European season:

• A cold, wet spell during rapid brood build-up in April and May — nurse bees cannot feed the whole nest.
• Colonies moved onto oilseed rape or into orchard pollination, where the brood nest expands faster than the bee population.
• Old, dark comb carrying a bacterial load from previous seasons.
• Shook swarms skipped for years in an apiary with a history of the disease.

What Happens Next

Where EFB is confirmed, the official response depends on the level of infection and national rules. In practice you will see one of:

1. Shook swarm — bees shaken onto fresh foundation, all comb destroyed, fed syrup. Effective for light infections and the most common outcome in Belgium.
2. Antibiotic treatment under veterinary supervision — increasingly restricted across the EU and not available to beekeepers directly.
3. Destruction — heavy infections, or repeat cases in the same colony.

Whatever the outcome, treat the apiary as a unit: inspect every colony on site, sterilise your hive tool between hives with a blowtorch or washing soda, and change gloves.

Tip: Make the Check Routine

You do not need a disease inspection. You need to look at uncapped larvae on two frames of every colony at every spring inspection, which adds about a minute. Log what you see — "larvae pearly, coiled" is a perfectly good record, and three years of that entry makes the abnormal frame obvious the day it appears.

Common Mistakes

• Only looking at sealed brood. EFB lives in the open cells.
• Blaming a spotty pattern on the queen and requeening without examining larvae.
• Sharing frames between colonies to even up strength during a suspected outbreak.
• Cleaning the hive tool in cold water. It moves spores and bacteria between hives.
• Waiting to report. Late reporting is what turns one hive into an apiary-wide standstill.

Field Note

Photograph any frame that gives you doubt, with the frame number and hive in the shot. If you do end up talking to an inspector, a dated photograph of the brood pattern from two weeks earlier is worth more than any description you can write down afterwards.