Bee Culture: Pests & Diseases

Acarine — Acarapis woodi

This is a small mite that lives in the first thoracic trachea of the honeybee.The female lays her eggs in the trachea which hatch into larvae after five days and then develop into adult mites about nine days later.The mites feed upon the blood of the bee, and although opinion seems to vary whether there are really any visible signs of this disease, it has no apparent effect on the bees, other than to shorten their life slightly.

Although various treatments have been used, at present none are approved for use in the UK.

Nosema — Nosema apis

Nosema is a Protozoan, which is a single celled animal, like an amoeba. At one point in it’s life it becomes a spore, in which form it can live for a very long time. It is the spores which are spread by and infect the bees. They multiply in the ventriculus of the bee until there are millions present in the bees gut, which inhibits digestion of pollen thus shortening the bees life.Spores are vacated by the bees in their faeces on to the comb when they’re unable to fly,e.g. in times of cold or bad weather. Thus spores are picked up by other bees when cleaning and can be digested,only to develop in the gut as before and the cycle repeats.

There are no signs to indicate the presence of Nosema, although there, of course, must be some voiding of faeces within the Hive to continue the infection. Although Nosema does not causes dysentery as we know it, Dysentery is no doubt a good method of spreading the infection.

Nosema has the effect of shortening the bee’s life by about half, although just how this effects the colony depends on how much it’s infested. The only practical symptom is that the colony doesn’t build up as fast as it should in spring, and nothing seems to make any difference. Colonies should recover naturally when the weather warms up enough to allow faeces to be voided in the field.

Diagnosis can be made with the help of a microscope, and once found you can treat with Fumidol “B” fed in sugar syrup. You can also fumigate all brood comb taken from the hive using 80 % Industrial Grade Acetic Acid. Combs are put into brood boxes, with entrances sealed, and a pad soaked in acetic acid is placed on top of the frames. This is repeated with subsequent brood frames until all are used. then the whole arrangement can be covered, in say polythene to keep the fumes in. After about a week the frames and boxes will be thoroughly fumigated. ( I’m told Acetic acid does not affect wax,stores, honey or pollen and all are safe to re-use with the bees.!)

Amoeba

As you would have guessed if you’ve read the section on Nosema, Amoeba are also protozoa. the difference here is that this parasite forms cysts in the malpighian tubules of the honeybee. They germinate, develop and then multiply in the ventriculus. The amoeba make their way back into the tubules where they form cysts , which pass through the small intestine, rectum and are voided by the bees. It apparently has no effect on the bee.

There is no treatment available for this, but it can be killed by sterilising the combs as discussed in the section on Nosema, above.

Dysentery

This is caused by too much water in the bee’s gut. It appears mainly in winter, due to possibly a number of reasons. Unripe Honey with high water content,crystallised winter stores, feeding with thin sugar syrup. By feeding thick sugar syrup in autumn, this is stored and used by the bees during the main part of winter, so reducing their intake of water.

Varroa — Varroa jacobsoni

This is a parasitic mite, living off of the Honeybee and breeding in the brood. Whilst it’s effect on the bees is difficult to quantify , the varroa mite is the cause of viral & bacterial infections entering via the wounds inflicted when the mite feeds from the bees. It is believed that these infections are more damaging than the mite itself. In the South of England we have experienced severe losses, with many people losing all their bees ! I have reproduced the text of a paper entitled Varroosis — a parasitic infestation of honey bees with the kind permission of the Central Science Laboratory, National Bee Unit , Ministry of Agriculture, Fisheries and Food, ( MAFF ).

Viral diseases

Whereas the adult bee diseases , Acarine, Nosema, Amoeba, Varroa etc seriously weaken colonies, it is viruses that are the real killers.Whilst there are various viral infections associated with the honeybee, Chronic Bee Paralysis Virus ( CBPV ) seems to be responsible for most deaths of colonies.

Watch for bees left on the top bars of frames after being smoked. they can be bloated, wings wider apart than usual, and the whole bee can be trembling. They also can fail to fly and can be found crawling around on the ground or up plant stems. They can lose their hair and appear darker. It is also possible to find heaps of bees in front of the hive. As the bees are dying daily this symptom can be distinguished from the effects of spray poisoning as bees at the top of the heap will be newly dead or paralysed, whereas those at the bottom will be more decomposed.

American Foul Brood

The causative mechanism of American Foul Brood’ ( AFB )’is a spore forming bacteria, Bacillus larvae. This is a “notifiable” disease and its presence must be notified to the Ministry of Agriculture, Fisheries and Food, ( MAFF )

The nurse bees feed the spores of AFB to the larvae, where they hatch into the bacterial form and multiply. The larvae die after the cell has been sealed. The larvae disintegrate, break down to a thick sticky mess before finally drying out to a hard scale on the lower part of the cell.

The cappings darken in colour, then sink, with some being perforated. The queen doesn’t lay where hard scale is present, so as the disease progresses the brood becomes very patchy, with lots of empty cells. Scale can be seen in the cells if the frame is held, top bar towards you, and tilted to catch the light in the lower half of the cells.

A good test for AFB is the so-called “matchstick” test. If a matchstick is poked into the cell, twisted a little to catch the contents, and then withdrawn, a “rope” can be pulled out from the cell. This is usually a definite indication of the presence of AFB.

Regardless whether AFB is suspected or found, it has to be reported to MAFF. Their instructions must then be followed, and if AFB is confirmed the colony destroyed.

European Foul Brood

The causative mechanism of European Foul Brood’ ( EFB )’is a also a bacteria, Melissococcus pluton, but unlike AFB this is non-spore producing. This is a “notifiable” disease and its presence must be notified to the Ministry of Agriculture, Fisheries and Food, ( MAFF )

The larva is fed the bacteria, which kills it before the cell is sealed. The bacteria actually feeds upon the larval food, so the larva dies of starvation ! As it is dying the larva changes from a nice pearly white to yellow or greyish brown in colour. As it dies before the cell is sealed the bees will throw out the dead larva and clean the cell. as larva are removed quickly by the bees once they are dead there is little evidence of EFB. If you have dead and twisted larvae , sometimes accompanied by a smell, then you probably have EFB.

This is a notifiable disease , so the treatment will be under the direction of MAFF and the local Foul Brood Officer.

Sac Brood

This is actually caused by a virus that infects the larvae which then die after the cell is sealed.The larvae which have been killed by this virus look like fluid-filled sacs, hence the name Sacbrood.

Diseased larvae change from the usual pearly-white colour to pale yellow, and the head curls up as the body dries to a dark brown scale in the cell. The larvae dries to a flattened shape with a slightly upturned head known as the Chinese Slipper effect. Because of this scale it can be confused with AFB. Adult bees recognise infected larvae and actually remove them from the hive. In addition any sacbrood virus in the dry scale of any remaining larvae soon becomes non-infectious.

There is no specific treatment for sacbrood, but luckily sacbrood is a transitory disease, i.e. it doesn’t hang around for long. Probably the only thing to do in very bad cases is to re-queen as there is some evidence that some strains can have an inherited susceptibility.

Chalk Brood

Chalk brood is caused by the fungus Ascosphaera apis. This germinates in the larvae and the thread-like strands of the fungus invades the body tissue of affected larvae until it is completely cocooned . This has the appearance of chalky white remains that fill the cell,with examples often scattered around the brood. Don’t confuse this with mouldy pollen, which is usually to be found around the periphery of the brood.

The fungus is spread by the spores, which being sticky, attach themselves to the bees or to the comb itself. Transferring infected combs from hive to hive can thus transfer the disease.

It is thought that stress in the hive can trigger the spores to germinate. This stress can be through a number of reasons — low temperatures in the brood, protein shortage or higher than normal levels of Carbon Dioxide,where there may not be sufficient bees to ventilate the hive properly.

Normally only one or two larvae are affected at a time. When the infection is much higher than this the only course of action is to re-queen.

Stone Brood

This is caused by a number of fungi, Aspergillus flavus or Aspergillus fumigatus and is common in Europe and the US, although not so in the UK.

The dead larvae are similar to that of Chalk brood, except that they appear yellow-green or grey-green depending upon which virus was the cause.

This fungi can affect humans, so do not sniff or smell the comb as you will get a respiratory infection, that is difficult to cure as the fungi are resistant to anti-biotics.

There is no treatment, other than to destroy the whole colony !

Chilled Brood

This is brood in all stages which is killed due to low temperature. This is caused by,or rather is the result of, a reduction in the number of bees required to keep the brood warm. e.g. starvation, spray poisoning or simply, mishandling by the beekeeper. I’ve read that unsealed larvae can survive for several hours, even days according to one source, at temperatures of around 65o F, so either the temperature drop has to be severe, or a combination of lowered temperature and neglect by adult bees thus causing starvation, combines to kill ( chill) the brood.

Large areas of the brood will die with larvae turning very dark, even black, in colour. there is no treatment, other than not letting it happen in the first place — it’s usually the fault of the beekeeper.

Addled Brood

References vary on the exact nature of this, however it seems that nowadays this is the name given to any brood disease that cannot be positively identified — there are many viral disease due to hereditary faults in the bees.

There is no known treatment, however practically you should re-queen with a different strain.

Bald Brood

Normally, pupae are sealed in their cells by wax cappings. On occasions, small groups or rows of cells remain uncapped revealing pupae beneath. This has been attributed to shortage of wax in the colony, to genetic traits of the bees, but is more likely to have been caused by the Wax Moth.

There is no treatment. The brood emerges normally in cases due to the genetic defects, with occasional damage to the emerging bees due to Wax moth faeces.

Wax Moth

In Britain we have two species of Wax Moth — the Greater Wax Moth Galleria mellonella and Lesser Wax Moth Achroia grisella. The Greater Wax Moth has a wing span of around 1 inch and is brown with white markings. The Lesser Wax Moth is as you would expect, smaller, having a wing span much less than an inch. Its lighter in colour and very active, running about on the comb. However, it’s the caterpillars that do the most damage as both feed upon wax and cocoons from brood comb, eating into them and so uncapping brood in the process. The wax moth larvae leave silk trails as they pass along beneath the wax cappings. Young adult bees can become trapped in this matt of silk as they emerge and die as a result. Strong colonies won’t tolerate the presence of wax moth so this shouldn’t be much of a problem to the beekeeper.

Braula coela

Braula coeca This is really a small wingless fly,living on the backs of the worker bees and the queen. It is ellipse shaped, upto 2mm in length, reddish in colour. They appear to do no harm to the bees but they spoil the cappings of the honeycomb as their larvae tunnel through.

What you have in your mind?