A frame of spotty, discolored brood is enough to make any beekeeper’s stomach drop, because the first thing that comes to mind is almost always American foulbrood, the disease that ends with a match and a shovel. Most of the time, though, that panic is aimed at the wrong culprit. European foulbrood causes brood that looks unsettlingly similar at a glance, but it’s a milder, treatable disease that rarely requires destroying anything. I’ve had a hive tested for both before the lab results came back, standing over the frames trying to talk myself down from the worst-case assumption, and the distinction matters enough that every beekeeper should be able to make it without a lab. Here’s how European foulbrood actually differs from American foulbrood, and what to do once you’ve confirmed which one you’re looking at.
What Is European Foulbrood?
European foulbrood is a bacterial brood disease caused by Melissococcus plutonius that kills honey bee larvae before their cells are capped. Unlike American foulbrood, the bacterium doesn’t form spores, which means it can’t survive indefinitely on equipment and doesn’t force a beekeeper into burning frames or hives. EFB is treatable, often manageable through hive strength and hygiene alone, and colonies frequently recover from it without any antibiotic intervention at all.
The USDA-ARS Bee Research Laboratory notes that European foulbrood is most common in spring when brood rearing peaks, that it can spread quickly or slowly depending on the colony, and that it usually subsides on its own by mid-summer as a strong honey flow helps the colony recover.
European Foulbrood vs. American Foulbrood: What Actually Separates Them
The two diseases get confused constantly because both cause discolored, dead brood and an unpleasant smell, but the underlying differences are significant enough to change how you respond.
| Trait | European Foulbrood | American Foulbrood |
| Cause | Melissococcus plutonius, non-spore-forming | Paenibacillus larvae, spore-forming |
| Smell | Mildly sour, sometimes barely noticeable | Strong, often described as glue-pot or sulfurous |
| Larval color | Yellow to brown, twisted in the cell | Yellow to brown to black, collapsed flat |
| Timing of death | Before capping, larvae 4 to 5 days old | Mostly after capping, in the pupal stage |
| Scale removal | Comes out of the cell easily | Sticky, ropes out, hard to remove |
| Treatability | Treatable, can resolve without antibiotics | Not treatable, spores survive decades |
| Regulatory response | Reportable in most regions, rarely requires burning | Reportable and often requires burning infected equipment |
How EFB Spreads: Why Larvae Die in Just Four Days
Nurse bees unknowingly do the spreading. A larva younger than about 24 hours old picks up Melissococcus plutonius through contaminated brood food, and the bacteria then multiply inside the larva’s gut, competing directly with it for nutrition. Because the bacteria are racing the larva for food rather than attacking its tissue the way American foulbrood does, an infected larva often dies of starvation within four to five days, usually before the cell gets capped at all.
That timing is why strong, well-fed colonies frequently shake off EFB on their own. When nurse bees can keep up with removing hungry, abnormal larvae fast enough, the disease never gets a foothold. It tends to hit hardest in colonies already under stress from cool, wet weather, heavy Varroa mite loads, poor nutrition, or pesticide exposure, since those same stressors slow down the colony’s ability to clean house.
Spotting EFB in the Hive: Symptoms and What They Look Like
The clearest visual sign is a spotty brood pattern with scattered capped and uncapped cells rather than the solid, uniform brood you’d expect from a healthy queen. Because EFB mostly kills larvae before capping, you’re looking at open cells, not the sunken or perforated cappings associated with American foulbrood.
Infected larvae typically turn from their normal pearly white to a dull yellow, then brown, and they’re often twisted or coiled unnaturally inside the cell instead of lying in the neat curled position of a healthy larva. The dead larvae dry into a loosely attached scale that lifts out of the cell without much resistance, a meaningful contrast to the ropy, sticky remains left by American foulbrood. The smell, when present, tends to be mildly sour rather than the heavier, more distinctive odor most beekeepers associate with a serious AFB outbreak, though a mild odor alone is never enough to rule EFB in or out on its own.
Diagnosing European Foulbrood the Right Way
Visual inspection gets you most of the way there, but symptoms genuinely overlap enough between the two diseases that a confirmed diagnosis matters, especially the first time you encounter either one. Field diagnostic kits, including lateral flow devices similar to a rapid antigen test, can confirm Melissococcus plutonius on the spot. Extension researchers at the University of Florida’s IFAS Entomology and Nematology Department recommend sending an unclear sample to a state apiary inspector or university lab rather than guessing, and it’s worth doing before committing to a treatment plan or, worse, destroying equipment you didn’t need to destroy.
If you suspect American foulbrood instead, the classic field check is the rope test: a toothpick or matchstick inserted into the dead larva and slowly withdrawn will pull a sticky, ropy thread if Paenibacillus larvae is present. EFB remains, by contrast, do not rope out, which is one of the fastest ways to tell the two apart without a lab. Some state apiary programs also use trained detection dogs that can sniff out American foulbrood before visible symptoms even appear, though that technology isn’t yet standard practice for European foulbrood.
Treating European Foulbrood Without Burning Anything
Because Melissococcus plutonius doesn’t produce spores, treatment options exist that simply aren’t available for American foulbrood. The most common non-antibiotic approach is a shook swarm: shaking the adult bees off the infected combs onto fresh foundation and discarding the old comb, which removes both the contaminated food stores and the bulk of the bacterial load in one move. Requeening with a strong, hygienic queen line can help as well, since more thorough hive-cleaning behavior gets diseased larvae removed before the bacteria multiply further.
Antibiotics, specifically oxytetracycline, remain an option in some regions when a case is severe or a shook swarm alone doesn’t resolve it. In the United States, that requires more than a trip to the local supply store. Since 2017, federal rules have classified honey bees alongside other food-producing animals, which means oxytetracycline can only be obtained through a prescription or a veterinary feed directive written by a licensed veterinarian, not purchased over the counter.
Consult your local apiary inspector or extension office before starting any treatment. Regulations, approved products, and reporting requirements for EFB vary by state and country, and a quick call before you act can save you a wasted treatment or an unnecessary equipment loss.
A Regulatory Patchwork: Why Treatment Rules Depend on Where You Keep Bees
It’s worth being transparent about how differently European foulbrood is handled depending on where a hive sits. In the United States, oxytetracycline is an approved, legal option once a beekeeper has the required veterinary prescription or feed directive. Cornell’s pollinator health program and several European Union countries take a stricter stance, where routine antibiotic use in honey production is heavily restricted or effectively prohibited because of concerns about residues ending up in honey and accelerating antibiotic resistance, which pushes many EU beekeepers toward shook swarms and colony management as the default response rather than medication. EFB also isn’t classified as notifiable at the EU level itself, even though individual member states, including the UK, do treat it as a reportable disease with their own monitoring programs. If you keep bees outside the United States, check your own country’s current rules before assuming any of the specifics above apply directly to you.
What This Looked Like in My Own Apiary
The season I actually had to tell EFB and American foulbrood apart, I didn’t have the luxury of waiting calmly for lab results. A hive had gone from a tight, solid brood pattern to something spotty and unsettling within about ten days, and my first instinct, like most beekeepers, went straight to the worst case. What actually told the two apart before the lab confirmed it wasn’t the smell, which was mild enough that I second-guessed myself more than once. It was the scale. When I worked a toothpick into a few of the dead cells, the remains lifted out clean instead of stretching into the sticky rope that would have meant American foulbrood and an immediate, mandatory teardown. That one field check changed the entire plan for the hive, from destruction to a shook swarm and a requeen, and the colony was back to a normal brood pattern within about six weeks.
If a colony near you starts showing a pattern like that, it’s also worth ruling out chalkbrood disease, a fungal brood condition that can produce a similarly spotty pattern but with a completely different cause and treatment path, and worth knowing apart from foulbrood before you commit to a plan.
Frequently Asked Questions
What is the difference between European and American foulbrood?
European foulbrood is caused by a non-spore-forming bacterium and is treatable without destroying equipment, while American foulbrood is caused by a spore-forming bacterium that can survive for decades and usually requires burning infected hives.
Can you treat European foulbrood?
Yes. European foulbrood often resolves with a shook swarm, requeening, and good hive hygiene alone, and antibiotics like oxytetracycline are available as an additional option in regions where regulations allow it.
Do I have to burn my hive for European foulbrood?
No. Because the bacteria that cause European foulbrood don’t form long-lived spores, burning is not the standard response the way it is for American foulbrood, and most colonies recover through management changes instead.
What does European foulbrood smell like?
European foulbrood typically has a mild, sour smell that’s far less noticeable than the strong, sometimes glue-like odor associated with a heavy American foulbrood infection, and the smell alone isn’t a reliable enough sign to diagnose it.
Is European foulbrood contagious to other hives?
Yes. It spreads through contaminated brood food, drifting or robbing bees, and shared equipment, so isolating an infected colony and avoiding equipment swaps between hives during an outbreak matters just as much as treating the original hive.
The Takeaway
European foulbrood earns its reputation as the disease beekeepers panic-diagnose into something worse than it is. The visual overlap with American foulbrood is real, but the scale test, the smell, and a lab confirmation when you need one will tell you which disease you’re actually managing well before you have to make any irreversible decisions. Treat the spotty brood pattern as a signal to investigate calmly rather than a reason to reach for matches, and in most cases, your colony has a real shot at coming back from it.
This article is educational and reflects general field practice; always confirm diagnosis and treatment choices with your local apiary inspector or agricultural extension office, since regulations and approved products vary by region.
