American Foulbrood – Deceptive and Deadly

American Foulbrood has paid a visit to a hive one of my bee yards.  It is the first time I have had a case of Foulbrood in over ten years of beekeeping  The hive has been destroyed.  The frames made a very nice fire.  The boxes got burned too, but that was an error – my husband got a bit carried away.  The tops and bottom screens have been scorched and wiped with bleach solution.


I’m a fan of the Bee Research Laboratory in Beltsville, Maryland –  and their diagnistic servies (  Whenever I suspect something’s wrong, I send a sample.  Until this time it has always been varroa or nosema.


All my equipment is bought new.  No frames in the hives are over five years old (they are dated).   There are a few other beekeepers near-by, and there are feral colonies of honeybees in the area.  American Foulbrood can originate from a beekeeper’s hive or feral hive.


Honeybee brood dead from AFB

American Foulbrood

Honeybee brood comb infested with varroa mites

Varroa Mite Infestation

American Foulbrood can look like brood that has been long dead from mites, if the AFB in the post-ropy “dry” stage.   Brood from a varroa infestation can look like AFB, if the hive has been dead a while (no living bees or mites).  The above image is a USDA image which shows living brood. In a long dead hive these would be all dried up.   This can include depressed cappings, holes in cappings, and even an odd smell.

AFB : dead brood being drawn out of cell

Ropy Stage of AFB

It’s easier to tell apart if either problem is in the early stages. Mites will be present in a mite infestation. In AFB the brood turns brown and if a thin stick or pin is inserted, the remains will draw out like a long string).

The short story is that I had three hives that looked like mite kill, but one had an odd odor to it.  Ah ha! Foulbood.   Frames from those hives were identified by a friend who has been beekeeping for over 30 years as AFB.  It turned out that hive, the one that smelled, was dead from varroa mites, not AFB (Bee Research Lab results).

However another hive I had tested did show positive for AFB.  It didn’t smell.


AFB can  fool the most experienced beekeepers.  Always check with the Bee Research Lab.


Or always check with the bee lab before you destroy anything

I was clearing out the seven dead hives from the past winter.  All of them had been strong hives over the summer with picture perfect brood patterns.  These teaming hives had gone into winter with full stores.  Four of the hives died by queen failure.  Three had other stories.

One hive in my first yard looked like death from varroa mite.  IMAGE.  Sad, but these things happen, not every “resistant” queen and her mates are perfect.  But this one had a different odor.  It was not the smell of sulfur, or “old socks”, or anything terribly pungent.  It just smelled dead. (If you live in the country where you periodically find that a mouse has passed away in storage area of your pick up, your tractor’s battery compartment, or that tool cupboard you forgot to shut, you’ll know the smell).

The “roping” test for American Foulbrood was not applicable here; these hives had been dead for months.  Scale was there, but that can be deceptive, as you’ll soon read.


I was going to visit a beekeeper friend the next day, with over 30 years in beekeeping experience.  He said “bring some frames down, I’ll look at them.”  I did and he said “Foulbrood.”

Back at the farm, I cut a square of the brood out of one of the frames, wrapped it in paper, put it in a box and put it in my office.  The hive was isolated, and all entrances were closed.

I then checked my records: Where did this hive come from?  Where was the queen from?  Were there any notes on anything odd in this hive last year?  It turned out that the hive was a split from another bee yard with an open-mated queen.  In fact, it was a split from a hive that had died during the winter and was on the next days autopsy schedule.


That hive and the dead-out next to it looked like a mite kill, but they had the same “dead” smell.  By now, I was smelling this everywhere: the kitchen, the libary, the gas station. Those hives got the same treatment as the other, including cutting out a sample.

All the hives were destroyed.  Fire, scorching, bleach…

THE EXPERTS SPEAK– and do diagnostics:

Then I posted the samples to the Bee Research Laboratory.  In hindsight it would have been better to post, wait for results and then destroy.

One hive did show Foulbrood, but NOT the hive that was indentified as Foulbrood by the an experienced beekeeper


1) Wait until you get your results back to destroy any hive.  Do isolate and lock up the hive in the mean time.  If it has living bees, make sure those bees cannot get out of their “lock up”.   It took about 10 days to get the results from the Bee Lab.

2) A varroa mites deadout can look like Foulbrood to even the most experienced beekeeper.  Yes, even down to the “scale” of dead larvae.  This hive probably died sometime in the late fall or early winter

3) Foulbrood can look like a varroa mite kill.  It might smel, but do not depend on it to smell like sulfur, rotten eggs, dirty socks. Don’t go with the smell.

4) To beat a dead horse (or hive in this case) : When in doubt send samples to The Bee Research Laboratory (  At this time the service is free, but even if they do start charging (these are hard times), it is well worth the money.  If folks who have been keeping bees for decades can get it wrong, we all can.

So now it’s just wait, watch, and monitor.  Other hives may have visited the infected hive or the location that the infected hive visited.  A bit nail-biting, but at least there was no robbing in the affected hive.  All my hives have strong stores left from last fall, and the rain has kept them in.  I’ll let you know what happens.

That’s the news from Brookfield Farm in Maple Falls.


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