Patchy dead brood after the cold snap — chilled brood, or am I looking at EFB?
Yorkshire first-year keeper trying not to spiral. We had that cold wet snap last week (down to 6°C at night) and yesterday's inspection showed a patch of dead brood on the two outer brood frames of my bigger colony. Some cells have greyish, deflated-looking larvae; but a few larvae elsewhere look twisted in the cell and a bit yellowish rather than pearly white, and now I've googled myself into a panic about European foulbrood.
Colony is otherwise busy, no smell that I can detect, queen seen, eggs present. The dodgy-looking larvae are uncapped. Is there a reliable way to tell chilled brood from EFB by eye, or is this a call-the-inspector situation? I know foulbrood is notifiable here and I'd rather look daft than spread something.
#efb#chilled-brood#diagnosis#bee-inspector
▲ 21 votes💬 4 replies✅ Solved
4 replies
KentishBee · Jul 1, 2026
Deep breath — the classic chilled brood picture fits your outer frames: it kills brood of ALL ages at once in the zone the cluster abandoned during the cold, so you get a defined patch at the edges, larvae grey to blackish, right after a cold snap. EFB is more scattered and it's specifically unsealed larvae dying, twisted or 'melted' in the cell, off-white turning yellow-brown. The fact that you saw a few twisted yellowish ones elsewhere is the bit I wouldn't sit on.
PerthshireBees · Jul 1, 2026 · ✅ Accepted answer
Ring your Seasonal Bee Inspector — seriously, that's the answer. EFB is notifiable in the UK, the NBU inspection is free, they carry lateral flow test kits that give you an answer at the hive in minutes, and they will not think you're daft; catching it early is literally what the system is for. Log into BeeBase, find your local inspector, describe exactly what you wrote here. Don't move any frames or equipment between colonies in the meantime.
ImkerinLena · Jul 1, 2026
Good advice above. One more field observation: chilled brood, sad as it looks, gets cleaned up within a week or two and the pattern behind it is normal. EFB persists and spreads as new larvae are infected. But do not wait two weeks to find out — the inspector visit is the correct move, and the twisted-yellowish description is enough to justify the call.
YorkshireNewbee · Jul 2, 2026
Update: inspector came out this morning, absolute gent. Lateral flow test negative for EFB — his verdict is chilled brood plus a couple of larvae likely chucked out mid-removal that looked worse than they were. Told me my cold snap timing and edge-of-nest pattern were textbook. Hugely relieved and very impressed with the whole system.