Apiculture Factsheet #202
European Foulbrood (EFB) affects bee brood and is caused by the
bacterium Mellisococcus pluton. The disease has been reported
worldwide and is generally not considered serious. EFB incidence is
generally higher when the colony is under stress due to poor
management, lack of forage, high colony density, prolonged damp
weather, etc. EFB most often
occurs in spring but has also been reported in late summer.
Young honey bee larvae become infected with M. pluton when
they are fed contaminated food. The bacteria multiply rapidly in the
mid-gut of the young larva, resulting in starvation just prior to
capping. Some larvae may survive and enter the pre-pupal stage but
die shortly thereafter. The bacteria can remain viable for several
years after the larva has died.
When the larva dies, it is in the coiled or twisted position and
will turn yellow to brown. It is suspected that prior to death, the
larva becomes restless and twists and turns. Approximately 10% of
the larvae die after capping and this often leads to misdiagnosis
because of the similarity to symptoms of American Foulbrood.
The odour of the infected brood is sour. Unlike American
Foulbrood, EFB-infected larvae don’t become ropy when a sample is
collected from a brood cell. Over time, the decaying brood will dry
up and form a rubbery scale, not brittle like AFB. The scale is
easily removed from the cell and used for microscopic examination.
When in doubt, collect samples from several cells with a
toothpick and place in a small plastic bag or plastic wrap. Place
the sample in an envelope and mail to the Apiculture office in
Abbotsford for identification. (Note: M. pluton is generally
not microscopically identified but instead, the secondary invader
Bacillus alvei is, characterized by its large spindle-shaped
Management and Control
At the start of the main nectar flow, EFB mostly disappears or
becomes non-detectable. The infestation may reappear in the fall.
Re-queening seems to help because certain bee lines appear less
susceptible than others (due to cleaning behaviour), and the
replacement of the queen involves a break in the brood cycle of the
For cleaning up an active EFB infestation, all frames with
significant numbers of affected cells should be removed and burned.
The recommended amount of antibiotics should be dissolved in 250 ml
of sugar syrup and sprayed or sprinkled onto the adult bees at least
twice, 4 days apart (refer to Factsheet #204 for dosage and handling).
- Inspect brood frames regularly and be familiar with
- Inspect frames before transferring bees or combs between
- Minimize robbing by preventing syrup spillage. Do not barrel
feed. Keep apiary clean and remove unused and old equipment.
- Establish hospital yards for colonies from different apiaries
that have EFB. Clean hive tools, smoker and gloves after
inspection of each apiary. Clean clothes regularly.
- Replace the queen every 1 – 2 years.
- Feed only clean pollen and honey to colonies.