European foulbrood

The bacterium Melissococcus plutonius

The disease is endemic throughout eastern Australia but is not known to occur in Western Australia.

• Brood has a pepperbox appearance (combs with many uncapped cells mixed with normal capped cells)
• Cappings which are concave and sometimes punctured
• Young unsealed larvae (3–5 days old) in a 'C' shape around the cell walls
• Dead larvae which are watery and pasty in appearance, and are yellow or brown/black
• Ropy brood (in old infections)
• Slightly sour or sometimes rotten faecal odour

The bacteria multiply vigorously in the gut of larval bees which have been given food contaminated with M. plutonius. If larvae survive and pupate, the bacteria are discharged with faeces and deposited in the bases and cappings of cells. Some of these bacteria find their way to other larvae.

EFB can also spread through:

• robbing infected hives
• transferring infected honey supers and combs to clean hives
• using contaminated beekeeping equipment
• feeding infected honey and pollen.

Prevention

• Prevent robbing
• Replace at least 3 brood combs each year
• Re-queen annually using a strain of queen with good hygienic behaviour
• Maintain good nutrition for the bees

Worker, drone and queen bee larvae are all susceptible to EFB infection. Larvae are most susceptible to infection when they are less than 48 hours old, and usually die while still in the coiled state. The larvae first turn yellow then brown.

In old larval remains, a secondary invading bacterium, Bacillus alvei is also commonly present.

Stress often causes EFB to break out. Stress can result from:

• poor nutrition
• working winter honey flows
• excess movements of hives
• insecticide poisoning
• sudden expansion of the brood, resulting in insufficient nurse bees.

The disease is usually noticed in early spring, and to a lesser extent in autumn.

You can send samples to the Biosecurity Sciences Laboratory to determine whether your hives are infected with European foulbrood.

When EFB infection is light, treatment is usually not required as the disease often disappears during a good nectar flow.

We recommend re-queening the hive as a treatment.