Diseases of the honeybee

Common diseases, parasites, pests, and ailments of the honeybee include:

• Varroa mites
• Acarine mites, formerly known as Tracheal mites
• American foulbrood (AFB)
• European foulbrood (EFB)
• Chalkbrood
• Nosema
• Small hive beetle
• Wax moths
• Chilled brood
• Pesticide losses

Varroa mites

Varroa destructor is a parasitic mite that feeds off the bodily fluids of adult, pupal and larval bees. Varroa mites can be seen with the naked eye as a small red or brown spot on the bee's thorax. Varroa is a carrier for a virus that is particularly damaging to the bees. Bees that were infected with this virus during their development will often have a visible "K-wing" deformity. Varroa has led to the virtual elimination of feral bee colonies and is a major problem for kept bees.

Varroa was first discovered in Southeast Asia in about 1904, but has now spread virtually worldwide. Varroa was discovered in the United States in 1987. see also

Varroa mites can be treated with commercially-available miticides. Miticides must be applied strictly according to the label in order to minimize the risk of contamination of honey that might be consumed by humans. Proper use of miticides will also help to slow the development of resistance among the mites.

Varroa mites can also be controlled through non-chemical means. Most of these controls are intended to reduce the mite population to a managable level, not to eliminate the mites completely.

• More and more beekeepers use a screened bottom board on their hives. When mites occasionally fall off a bee, they must climb back up to parasitize a new bee. If the beehive has a screened floor with mesh the right size, the mite will fall through and can not return to the beehive. The screened bottom board is also being credited with increased circulation which reduces condensation in a hive during the winter.
• Powdered sugar, talc or other "safe" powders can be sprinkled on the bees. The powder does not harm the bees (and, if you use sugar, can even become a small source of feed), but does cause some of the mites to dislodge. Powdered sugar works best as an amplifier of the effects of a screened bottom board.
• Freezing drone brood takes advantage of varroa mites' preference for larger drone brood. The beekeeper will put a frame in the hive that is sized to encourage the queen to lay primarily drone brood. Once the brood is capped, the beekeeper removes the frame and puts it in the freezer. This kills the varroa mites that are parasitizing those bees. It also kills the drone brood, but most hives produce an excess of drone bees so it is not generally considered a loss. After freezing, the frame can be returned to the hive. The nurse bees will clean out the dead brood (and dead mites) and the cycle continues.

Several attempts have been made (and are continuing) to breed bees with an increased resistance to varroa mites. In fact, the Africanized honeybee was originally an experiment to cross-breed mite resistance into the European honeybees common in the Americas.

Acarine mites

Acarapis woodi is a small parasitic mite that infests the airways of the honeybee. The first known infestation of the mites occurred in the British Isles in the early 20th century. First observed on the Isle of Wight in 1904, the mystery illness known as Isle of Wight Disease was not identified as caused by a parasite until 1921. It quickly spread to the rest of Great Britain. It was regarded as having wiped out the entire bee population of the isles (later genetic studies have found remnants that did survive) and dealt a devastating blow to British beekeeping. Brother Adam at the Buckfast Abbey developed a resistant hybrid bee known as the Buckfast bee, which is now available worldwide to combat acarine disease.

Diagnosis for tracheal mites generally involves the dissection of a sample of bees from the hive.

Acarine mites, formerly known as tracheal mites are believed to have entered the US in 1984 via Mexico.

Mature female acarine mites leave the bee's airway and climb out on a hair of the bee where they wait until they can transfer to a young bee. Once on the new bee, they will move into the airways and begin laying eggs.

Acarine mites are commonly controlled with grease patties (typically made from 1 part vegetable shortening mixed with 3-4 parts powdered sugar) placed on the top bars of the hive. The bees come to eat the sugar and pick up traces of shortening which disrupts the mite's ability to identify a young bee. Some of the mites waiting to transfer to a new host will remain on the original host. Others will transfer to a random bee - a proportion of which will die of other causes before the mite can reproduce.

Menthol, either allowed to vaporize from crystal form or mixed into the grease patties, is also often used to treat acarine mites.

American foulbrood

Bacillus larvae is a spore-forming bacterium. This disease only affects the bee larvae but is highly infectious and deadly to bees. Infected larvae will darken and die. Lab testing is necessary for definitive diagnosis, but a good field test is to touch a dead larva with a toothpick or twig. It will will be sticky and ropey (draw out). Brood also has a characteristic odor, and experienced beekeepers with good smellers can often detect the disease upon opening a hive. In the photo at right, some larvae are healthy while others are diseased. Capped cells with decomposing larvae are sunken, as can be seen at lower right. Compare with healthy brood at: Brood (honeybee).

Chemical treatment of American foulbrood is possible using oxytetracycline hydrochloride, but because of the persistence of the spores (which can survive up to 40 years), the most common treatment is the destruction of the colony and burning of all equipment.

Chemical treatment is sometimes used prophylactically, but this is a source of considerable controversy because the bacterium seems to be rapidly developing resistance.

European foulbrood

Melissococcus pluton is a bacterial brood disease that infests the guts of bee larvae. European foulbrood is less deadly than American foulbrood. European foulbrood does not form spores, though it can overwinter on comb.

European foulbrood is often considered a "stress" disease - a disease that is dangerous only if the colony is already under stress for other reasons. An otherwise healthy colony can usually survive European foulbrood. The disease may be treated chemically with oxytetracycline hydrochloride.

Chalkbrood

Ascophaera apis is a fungal disease infests the gut of the larva. The fungus will compete with the larva for food, ultimately causing it to starve. The fungus will then go on to consume the rest of the larva's body, causing it to appear white and 'chalky'.

Chalkbrood is often considered another "stress" disease because the fungal spores are always present but are managable by an otherwise healthy colony. Chalkbrood is most commonly visible during wet springs. Hives with Chalkbrood can generally be recovered by increasing the ventilation through the hive and/or by requeening the hive.

Nosema

Nosema apis is caused by a spore-forming protozoan that invades the intestinal tracts of adult bees.

Nosema is normally only a problem when the bees can not leave the hive to eliminate waste (for example, during an extended cold spell in winter or when the hives are enclosed in a wintering barn). When the bees are unable to void (
Slimed by hive beetle larvae
Hives infested at this level
will drive out bee colonies.