Brown streaks down the front of two hives in mid-September — dysentery or nosema, and what can I do without fumagillin?
Fifth year in Małopolskie, ten hives. After a warm start to the month we've had ten days of cold rain and the bees have been stuck inside. Two of the ten hives now have brown-yellow streaks below the entrance and on the landing board, and there's a sour smell when you get close. The other eight are clean.
Some things about those two: they're in the shadiest corner of the apiary right on the forest edge. One of them got a batch of syrup three weeks ago that had a faint yeasty smell — I used it anyway, which I already regret. And both brought in a lot of fir honeydew this summer that I left in the brood boxes as winter stores.
Is this nosema? I don't own a microscope. There's no fumagillin in the EU and I keep reading that nothing else actually works. What do I do this autumn, and what should I stop doing?
Streaks are dysentery — a symptom, not a disease — and you've named the two likeliest causes. Honeydew is full of indigestible solids, and bees wintered on it soil the hive when they can't fly. Fermented syrup does the same. Nosema is confirmed only by microscope (20 bees crushed, spore count — your regional lab does it cheaply), and Nosema ceranae often causes no dysentery at all. Now: dump that syrup; feed fresh 2:1 and swap the honeydew-heavy frames for capped syrup; get those hives out of the shade, tilt forward, dry floors. In spring, clean comb and 80% acetic acid on the old.
ImkerinLena · Sep 20, 2026
Agree with DrentseBij, and the honeydew point is the big one. In Bavarian forest apiaries wintering on Waldhonig is the classic cause of winter dysentery — we extract it and feed sugar back, every year. Two of ten hives streaking in the same weather tells you the difference is those two hives: the shade, the syrup, the stores. Do send bees for a spore count anyway; a high count in autumn changes what you do with that comb in spring, and it is a few euros.
SkaneBees · Sep 20, 2026
The acetic acid comb fumigation works and is cheap, since you'll want it in spring: 80% acetic acid, a pad soaked with roughly 150 ml laid on the top bars of each box, boxes stacked and sealed for about a week, then aired for a week before use. Empty comb only, no bees and no honey. It is corrosive — gloves and goggles, and it rusts any metal it touches. It kills nosema spores and wax moth eggs in one go.
PasiekaOlek · Sep 21, 2026
Syrup dumped and the bucket scrubbed. Fresh 2:1 on both hives tonight, honeydew frames coming out at the weekend for capped syrup from the strong hives. A sample of thirty bees is going to the bee institute in Puławy on Monday. And I've started moving the two hives a metre a day toward the sunny end. Thank you DrentseBij, that is the first clear answer I've had to this.