Diseases

Brood Diseases

It is essential to be able to recognize healthy brood – anything that deviates from this is suspect. Many causes of disease are to be found in most colonies, but infection is not usually apparent until the colony becomes stressed. Avoid stressing colonies and unhygienic procedures e.g. exchanging combs, spilling sugar syrup, etc.

  • Sacbrood is a virus disease (Morator aetatulae) found in 30% of colonies, usually noticed from May to early summer, when the ratio of brood to bees is high. Old beekeeping books refer to Addled Brood now identified as Sacbrood (Yates). Sacbrood disease prevents larvae from pupating (5 th moult) once they have been sealed in their cells. Larvae that have died from sacbrood become fluid-filled sacs stretched on their backs with their heads towards the top of their cells. Adult worker bees eventually uncap them. Diseased larvae turn from pearly white colour to pale yellow and the head curls up as the body dries to a thin, dark brown scale. Unlike American Foul Brood, the scale has a distinctive Chinese slipper shape and is easily removed in one piece. Adult bees recognize and remove affected larvae. Adult bees can be infected by feeding on contaminated pollen or by ingesting larval body fluids – the virus multiplies and collects in the hypopharyngeal glands that produce the food given to young larvae. However, infected bees cease to eat pollen and cease to feed larvae. Sacbrood is usually transitory and not a matter of concern. Combs can be re-used – the virus becomes non-infectious within a few weeks.
  • Chalk Brood is caused by the fungus Ascophaera apis, widespread and found in seemingly unaffected colonies – often appears in the Spring in expanding colonies. The trigger is not completely understood. High carbon dioxide levels in the brood nest, as may occur if there are insufficient bees to ventilate the colony, and deficiencies of pollen are possible factors. It may also be genetic, in which case re-queening may be the cure. The fungal spores are ingested by the larvae and germinate in the gut. Strands of fungus invade the larval tissue and the larva dies, frequently after the cell has been capped. The dead larva is chalky white at first, often with a yellow centre, and becomes very hard and loose in the cell (mummies). Additional black/grey spores may develop on the surface. Mummies are removed by house bees and can be seen outside the hive or on the floor. Chalk Brood mummies should not be confused with discarded mouldy pollen, which has coloured layers. Combs can be sterilized using acetic acid.
  • American Foul Brood is caused by the spore forming bacterium Paenibacillus larvae larvae. The spores contaminating the brood food develop into bacteria that penetrate the gut wall and multiply in the larval body tissues. The larvae usually die after the cell is sealed from ’blood poisoning’. The comb has a pepper box appearance where diseased larvae have been removed. Cappings may appear moist, sunken and perforated. Initially the dead larvae are slimy and dry to form brown scales, which can be seen if the comb is tilted to the light. The scales are difficult to remove and are highly infective – spores have been known to be viable after many years. Diagnosis can be confirmed by the ‘ropiness test’: a matchstick is inserted into a suspect cell, twisted and withdrawn slowly. If AFB is present the larval remains will be drawn out as a brown mucus thread. AFB is a notifiable disease – the BDO will arrange for bacteriological confirmation. A standstill order will be put in place. If confirmed, the BDO will supervise the burning of bees and combs. Bee Disease Insurance provides compensation. Do not feed foreign honey or honey of unknown origin, which may contain AFB spores. Swarms, drifting and robbing may bring AFB. You are not allowed to treat with antibiotics.
  • European Foul Brood is caused by the bacterium Melissococcus plutonius. The bacteria feed on food in the larval gut and starve the larvae. Larvae usually die before the cell is sealed. Affected larvae are seen in unnatural positions (‘stomach ache’), colour changes from pearly white to cream and eventually dry to form a brown scale (removable by the bees). In early stages, infected larvae have a melted wax appearance. Cell contents do not rope. EFB is a notifiable disease. The BDO will obtain microscopic confirmation. If confirmed, treatment with antibiotics by the BDO may be used if the infection is light – a shook swarm method of treatment may be recommended.

N.B. American & European are not geographical terms – both occur in Europe & America. Foul refers to the smell associated with the decomposition of the brood.

  • Varroasis is not a disease but an infestation by the parasitic mite Varroa destructor (previously jacobsoni). Since reaching this country in 1992, it has become endemic throughout the U.K. and most of the world. Your colonies will have varroa mites. Doing nothing is not an option – without treatment colonies will die within 3 years (there are no long-standing feral colonies). You must learn to monitor colonies for levels of infestation and treat when necessary with the approved varroacides in the correct manner – failure to keep to the time-scale has resulted in resistant mites. Fit varroa screens to hives in order to monitor levels of infestation. Uncap drone brood. Place a super frame in the middle of the brood box and destroy the drone brood built under the frame (varroa mites prefer drone brood). You must remove the brood traps – leaving them will have the opposite effect! 1,000 mites is now taken to be the highest acceptable population. Treat with Apistan/Bayvarol or Apiguard – other treatments may be time-consuming, temperature dependent, ineffective or pose a health risk to bees or humans (especially formic acid). Mite resistance requires Integrated Pest Management, a combination of methods used at different times of the year. There is no 100% knockdown treatment. Varroa breeds in sealed cells of brood – since a newly hived swarm has no brood, it can be treated to give a clean start. Apart from seeing mites, you may see stunted bees with distorted wings resulting from the varroa mite sucking the larval ‘blood’ – this is usually an indication of a high level of infestation. The puncturing of the larvae enables non-apparent viruses to take hold such as Slow Paralysis Virus and Deformed Wing Virus (Acute, Chronic, Cloudy Wing Viruses) – the colony dies from virus infection. Although varroa is now endemic in the UK and from 2005 will no longer be a statutory notifiable disease, the NBU will continue to offer advice on its control as it does for other serious nonstatutory diseases. http://beebase.csl.gov.uk/

Average Daily Natural Mite Mortality

Jan – March <2 no action 2-7 plan future control 7> consider control

April – June <1 no action 1-7 light control 7> severe risk

July – Aug <2 no action 2-8 light control 8> severe risk

Sept – Dec <6 no action 6-8 light control 8> severe risk

Light control might be drone brood culling, artificial swarming, dusting with icing sugar, etc. rather than heavy control using chemicals.

  • Stone Brood is caused by a fungus, either Aspergillus flavus or Aspergillus fumigatus. It is extremely rare and only mentioned because you will come across it in books!
  • Neglected Drone Brood. This is not a disease but a condition, which can be confused with EFB during the discoloured larvae stage or AFB at the scaling stage. The cause is a drone laying queen or laying workers. Drone brood is raised on worker cells resulting in stunted and malformed drones. The colony is usually small and will have dwindled, the bees eventually neglect the drone brood in worker cells, which then die of starvation before sealing. They decompose and become yellow to brown. The decomposing larva becomes a brown watery mass (which does not rope) and eventually dries to a scale which can be removed by the bees.

Adult Diseases

  • Acarine is an infestation by the mite Acarapis woodi. The Isle of Wight disease in 1904 – 1920s was probably acarine. Despite the signs of acarine given in beekeeping books, there are no visible external signs – the signs usually given (crawling bees, dislocated wings, etc.) are those of Chronic Bee Paralysis associated with acarine (although not proved as a vector). The mites infest the trachea. Dissection and microscopic examination (20x) of the first thoracic trachea can confirm diagnosis. Send a sample to a microscopist (in a paper container not plastic). There is no approved medicament in the U.K since FolbexVA was withdrawn in early 1990 and Frow Mixture was banned. Oil of Wintergreen and menthol have been used as a treatment and creosote! The life of an infected bee is shortened. It usually has little effect in the active season. The mite is spread from old bees to very young bees. A severe winter may cause an infected colony to dwindle in the spring. Some strains of bees are more susceptible than others – the ‘tracheal mite’ is a huge problem in the U.S.A which uses Italian/NZ crosses. There are external acarine mites: A. exturnus, A. dorsalis & A. vagans – little is known about them.
  • Nosema is caused by Nosema apis, a spore forming protozoa. The protozoa multiply in the ventriculus (30 – 50 million spores) and impair the digestion of pollen thereby shortening the life of the bee. The spores are later excreted. There are no obvious signs of nosema, although Dysentery (q.v.), excreta on combs and hive, frequently accompanies heavy infections. Bees normally defecate away from the hive – sometimes the bees defecate in and about the hive because of the excessive build up of waste matter in their guts. The excreta containing spores is cleaned up by the bees and they become infected. Infected colonies fail to build up normally in the spring. Dead bees may be seen outside the hive after cleansing flights. Confirmation of Nosema is by microscopic examination (400x): 30 bees are crushed in water and a droplet is examined for white, rice-shaped bodies. Send a sample to a microscopist in a paper container (not plastic). Nosema is the most common disease and is to be found in seemingly healthy colonies. In Infectious Diseases of the Honey Bee (Dr. Bailey & Brenda Ball), it is stated that of 80 apparently healthy colonies, 79 contained the spores of nosema. Avoid crushing bees which can release millions of spores. Replace and sterilize combs with 80% acetic acid (100 ml./brood box for one week – air before use). Treatment with the antibiotic Fumidil B (prepared from Aspergillis fumigatus the causative agent of Stone Brood!) inhibits the spores reproducing in the ventriculus, but does not kill the spores.
  • Amoeba is caused by a protozoan amoeba-like parasite Malpighamoeba mellificae. Cysts are ingested with food and germinate in the rectum. They migrate to the malpighian tubules (the ‘kidneys’) to create more cysts that then accumulate in the rectum and are excreted. The infection seems to have no effect on the colony, there are no specific symptoms and no treatment. Often seen under a microscope when examining a sample for nosema – grainy circular cysts, larger than the rice shaped nosema spores. The spores are destroyed by acetic acid.
  • Since colonies have been treated for varroa, you are unlikely to see a similar (and harmless) parasite Braula coeca, the bee louse, a wingless fly. Braula (which has 6 legs, varroa has 8) breeds under cell cappings. Adults feed on honey taken as queen or workers are feeding. Tunnels can spoil appearance of comb honey.
  • Viruses. Nosema, acarine, varroa, etc. in themselves do not kill a colony – they weaken it and thereby allow viral infections to take over. It is for this reason that Dr. Bailey considers that it was viral infection (Chronic Bee Paralysis Virus?) and not acarine that killed so many colonies in the Isle of Wight Disease – the symptoms described such as crawling bees, trembling wings, etc. are those of CBPV. It is only in recent years that viruses have been identified using the electron microscope. There are no cures for viral infection, they are immune from any antibiotic treatment. Viruses only multiply in living cells of their hosts and any medicament which kills the virus would kill the host. In practice, most colonies terminally weakened with nosema or acarine exhibit signs of CBPV, particularly clustering on top bars and continual trembling.

Management

  • Chilled Brood is not caused by a pathogen. The optimum brood temperature is 35º – 37ºC. If there are insufficient bees to maintain this temperature, the brood will die. In the Spring the queen may have laid a patch of brood that the bees can’t cover if the temperature drops. Spray poisoning (q.v.) may reduce the number of bees. A characteristic is that brood of all stages, sealed and unsealed are affected. The outer boundaries of the brood cluster are affected first as the bees retreat to maintain the inner core at the correct temperature.
  • Dysentery is not a disease but a condition caused by excessive build up of waste matter in the rectum i.e. diarrhoea. It is usually due to unripe honey/late feeding, granulated stores, fermenting stores, feeding brown sugar, etc. The signs are fouling of combs, hive parts and around the entrance. Dysentery is usually associated with nosema. A badly affected colony will be weakened and may succumb to viral infection. Soiled comb should be replaced and sterilized.
  • Poisoning. A sudden reduction in the number of foraging bees, a large number of dead or dying bees outside the hive, may indicate poisoning by bees alighting on sprayed crops. Legislation has reduced the number of incidents. Apart from the evidence of dead bees, the colony may become bad tempered and shivering, staggering and crawling bees may be seen (similar to CBPV). Returning foragers spin around on the ground until they die. Dead bees usually have their proboscis (‘tongue’) extended. If you suspect poisoning, contact your association’s Spray Liaison Officer. Note time and day and try to locate location and time of spraying and witnesses. If possible take 3 samples of 200 dead bees – use a paper or cardboard container not plastic – bees carrying pollen loads are useful in identifying the source of the problem. Send one sample to the National Bee Unit, Sand Hutton, Yorkshire, YO4 1BF, including all known details. Keep the remaining two samples in the deep freezer for future use. Do not expect a speedy response. If the colony is badly depleted reduce the entrance to guard against robbing.
  • Starvation. A preventable ‘disease’ – the beekeeper should never allow colonies to starve because of mismanagement. Many years ago, MAFF (as it then was) conducted a survey on winter losses and found starvation to be the major cause. Heft your hives! Starvation can occur at any time of the year, but especially in the spring when there is brood and little food coming in. Poisoning will reduce foraging. The signs are sucked larvae being thrown out, drones evicted, and immobile bees. When regular inspections are being undertaken, check that there is a minimum of 10 lb. of stores each week – this is based on a conservative estimate of 1 – 1.5 lb. per day. A full brood comb holds about 5 lb. and a super comb about 3 lb. of honey.
  • In the autumn, colonies have to be fed sufficiently and early enough for them to ripen and store food, where they can reach it when conditions are freezing. Bees can starve surrounded by plenty. “Spring feeding should be done in the autumn”! Ensure colonies have about 40 lb. sealed stores to see the colony through the winter. Emergency action involves spraying warm syrup on immobile but living bees, pouring sugar syrup into empty comb cells, and feeding with a contact feeder. It is generally too cold for bees to take down syrup (1 kg/1 litre) until early March. The simplest alternative method of feeding is to make a hole in the side of 1 kg. bag of sugar, dunk the bag briefly in water, then place it over the feed hole of the crown board, just above the cluster (add another super or eke & top crown board). Fondant, homemade candy and commercial feeds may also be used.
  • Healthy but weak colonies (3-4 seams) should be combined in the autumn. “The best packing for bees is bees”. Be careful not to overfeed and, therefore, overwork the bees in a nucleus. The loss of, say, 1,000 bees in a full colony can be supported. The same number dying in a small nucleus could be more than it can bear.
    The classic signs of starvation are of bees with their heads in the cells and their abdomens protruding. Some bees in the middle of the cluster will have crawled into empty cells. So when the clustered bees die and fall away, these cell dwellers are left behind. Dead bees in cells are therefore thought to be indicative of starvation. Colonies deemed to have died from starvation usually have no food or food out of reach.

Pests

  • Bald Brood. The Greater Wax Moth (Galleria mellonella) larva hatches among the brood and chews its way through brood cappings in a straight line. The bees remove the silky tunnels and leave the bee larvae bare which are not recapped. Bald Brood may also be caused by a genetic trait. There is no treatment – the brood emerges normally but is sometimes crippled with deformed wings and legs due to faecal pellets from the wax moth larvae. Stored comb is vulnerable to damage since the larvae feed on wax, larval skins and pollen. Protect stored comb by stacking boxes, placing newspaper between each box, and using Paradichloro-Benzine crystals (eggs are not killed) – there is a slight risk of contaminating honey. PDB is probably no longer available. Certan is a solution of Bacillus thuringiensis and is sprayed on the combs – the larvae die after ingesting the insecticide. Deep freezing kills all stages of wax moth. Acetic acid kills all stages. Greater Wax Moth has become more evident in recent years – maybe resulting from the loss of feral colonies and the use of varroa screens under which they pupate. The larva scoops out a boat-shaped depression in a wooden part of the hive and in this spins its cocoon and pupates. Combs can be attacked in weak colonies. The Lesser Wax Moth (Achroia grisella) can cause similar problems. The Greater Wax Moth has a wingspan of up to 3.6 cm. and the Lesser Wax Moth a wingspan of 1.8 cm.
  • Beekeepers opening hives in the cold, ‘spreading brood’, filling observation hives, moving bees, removing honey … and Vandals.
  • Autumn preparations should include taking precautions against pest damage to hives and colonies. Wasps and bumblebees should be kept out of hives. In the winter all outside hives are at risk from mice and in many locations hives are also vulnerable to damage by woodpeckers and badgers, etc.
  • If a colony dies, the hive should be closed to prevent robbing and the cause of death ascertained.
    The combs from dead colonies need assessment. Dispose of any combs that are really dark coloured or unsatisfactory – if you can not see sunlight through a brood comb, then it is too old. You can save the wax. Frames can be cleaned by immersion in boiling water and washing soda (an old Burco boiler is ideal). You could burn the lot and start again! Usable combs can be exposed to the fumes of 80% acetic acid (but don’t expose yourself) which will kill nosema spores, EFB bacteria, the early stages of wax moth larvae and chalk brood spores in about 10 days. The hives should be cleaned and scorched with a blowlamp – don’t be over-enthusiastic.
  • Colonies that appear sick, e.g. not building-up in the spring, should be left alone. Feeding may help if they are short of food. Otherwise, give them a small entrance and leave them alone. In April, sick colonies can be united. Don’t unite sick colonies to healthy ones. Keep only the combs with brood and deal with the rest as above. As soon as the queen in the united colony is laying, the broodnest can be lifted above an excluder leaving the queen below. Three weeks later, the old brood combs can be removed.

The movement of food as well as bees around the world may bring more problems. Tropilaelaps clareae is a mite which has been found infesting colonies of Apis dorsata and Apis mellifera in the Far East. The Small Hive Beetle (Aethina tumida Murray), native to southern Africa, was found in the USA in 1998 and is causing widespread damage to colonies. Both are notifiable diseases.

I hope you are one of those lucky ones who never lose a colony. If you are, I expect that when you toss a coin you can guarantee it will land on its edge. The rest of us will be doing some cleaning up in the meantime. Adrian Waring – BeeCraft, March 2003.

Sick bees collect less honey…

Dead bees collect no honey!