Every Beekeeper's Nightmare; Focus on Foulbrood

Updated: Sep 3, 2019

Positive ropiness test for AFB *

Foulbrood is a subject covered on any beginner's beekeeping course worth its salt, and with good reason. Although most beekeeper's will make it through their beekeeping "career" without having to deal with AFB, the impact of the disease on a colony - and surrounding apiaries - is so profound it is essential for anybody keeping bees to be able to spot the signs should they be unlucky enough to come across an infected colony.

This month a case of AFB has been confirmed in Wales.

But what is AFB and where does it come from? What can we do as beekeepers to minimise the risk of an outbreak developing?

What is foulbrood?

Foulbrood refers to two diseases which can effect honeybees; American foulbrood (AFB) and European foulbrood (EFB). These names can be misleading as they do not refer to geographical distribution of the disease, instead they refer to the area in which they were first scientifically investigated. Both diseases are highly contagious and can easily spread between apiaries int he local area.

Both types of foulbrood are classed as statutory notifiable diseases. This means that beekeepers are legally obligated to report any colonies they suspect may be infected under the Bee Diseases and Pests Control Order 2006.

AFB infection is caused by a spore-forming bacterium called Paenibacillus larvae. Infection begins when a honeybee larva ingests bacterial spores when it is fed contaminated food by nurse bees. These spores germinate in the gut and cause it to die after the cell is capped. Millions of infective spores are present in their remains - called 'scales' - which adhere to the wall of the cell and are not easily removed by housekeeping bees. Infective spores are highly resistant to extremes of heat and cold and are not killed by disinfectants, and they remain viable for many years in honey or on stored brood combs. AFB normally results in the death of a colony.

"Pepperpot" brood pattern and scales in AFB *

Signs of AFB infection:

  • Sunken and/or perforated brood cappings where larvae have died underneath

  • "Pepperpot" (patchy) brood pattern caused by dead brood

  • Cappings may look greasy or moist

  • Presence of "scales" in empty cells

  • Positive "ropiness test" on contents of dead cells - when a matchstick is inserted the contents stretch 10-30mm

If you are ever unsure call your local bee inspector!

EFB is caused by the bacterium Melissococcus plutonius, which multiplies in the mid-gut of infected larvae and competes with it for food. Larvae typically die from starvation shortly before the cell is capped, therefore a sign of EFB is the presence of dead uncapped larvae, often in an abnormal position different from that of healthy larvae ( which are normally coiled in the bottom of the cell). EFB can develop over months/years and does not always kill a colony.


Burning AFB-infected frames and comb. Photo courtesy of FERA, Crown copyright

There is currently no treatment for AFB. To prevent spread of the disease, infected colonies are killed and burned in a pit along with the contaminated frames and comb, under the supervision of a Bee Inspector. Hives and tools can be sterilised by thoroughly scorching with a blow torch, and other equipment (gloves, footwear, bee suit, smoker) should be washed thoroughly in washing soda or hot soapy water. The use of antibiotics to control AFB is not permitted in the UK.

Treatment of EFB depends on how heavily infected a colony is. A light infection with EFB is normally treated with a shook swarm (.pdf). Antibiotics may be administered by a NBU Official to tide a strong colony over winter if the infection is found too late in the season to perform a shook swarm immediately, then the shook swarm is done the following spring. Bee Diseases Insurance Ltd (BDI) support the practice of shook swarming all the colonies in an apiary where one case of EFB is found on the basis that spread within the apiary is highly likely. If a colony is more heavily infected with EFB then it is destroyed.

Reducing the risk

There is no way of guaranteeing your colonies protection from foulbrood, but you can certainly reduce the risk of both AFB and EFB:

  • Maintain strong, healthy colonies with young vigorous queens - this seems to be the answer to most beekeeping dilemmas! If a colony is looking weak towards the end of the year, merge it with a stronger one after ensuring both colonies are disease-free

  • Practice good hygiene - if you have several hives then changing gloves and washing your hive tool in washing soda between hives is good practice

  • Beware of buying second hand equipment - and if you do, be sure to sterilise it with a blowtorch before use. Never buy second hand comb

  • When buying bees, ALWAYS ensure they have been inspected by a regional bee inspector - never buy bees unless they have been checked, especially as a beginner. Large commercial suppliers e.g. Thornes will have been certified as disease-free (hence the price tag). Paying a premium for healthy strong bees will always be cheaper than having to burn all your hives! This goes for buying queens too

  • Never feed your bees honey, unless it is their own (e.g. wet supers or cappings) - supermarket honey is generally made from large batches of mixed imported honey from all over the world. If there are AFB spores in any of these honey sources then you are feeding them to your bees and risking infection. Sugar syrup is cheaper and won't make them sick

  • Keep an eye out for the signs of AFB when inspecting your hives - the earlier it is caught the easier it is to contain. If you are ever unsure get the local bee inspector to have a look! It will not cost you anything and you could potentially be saving many colonies from infection

  • Replace brood comb regularly - NBU suggests replacing 1/3 to 1/2 brood comb per brood box per year

  • Register your hive on Beebase! This greatly helps in monitoring and preventing the spread of bee diseases in the UK. Registering your hive is free and you will be notified if there are any problems in your area

Healthy-looking brood and bees

Further reading

* Image © Crown copyright 2017; Foulbrood Disease of Honey Bees and other common brood disorders. Full text available from www.nationalbeeunit.com

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