Diseases of the honey bee
From Wikipedia, the free encyclopedia
Common diseases, parasites, pests, and ailments of the honey bee include:
[edit] Varroa mites
Main articles: Varroa destructor
Varroa destructor and Varroa jacobsoni are parasitic mites that feed 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 are 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 in many areas and is a major problem for kept bees in apiaries. Some feral populations are now recovering — it appears that they have been naturally selected for varroa resistance (these so-called feral populations may be africanized 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, in New Zealand in 2000.
Varroa is generally not a problem for a hive that is growing strongly. When the hive population growth reduced in preparation for winter or due to poor late summer forage the mite population growth can overtake that of the bees and can then destroy the hive. Often a colony will simply abscond (leave as in a swarm, but leaving no population behind) under such conditions.
[edit] Acarine (Tracheal) mites
Acarapis woodi is a small parasitic mite that infests the airways of the honey bee. 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 and microscopic examination 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.
[edit] Treatment
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.
[edit] American foulbrood (AFB)
Paenibacillus larvae (formerly classified as 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 be sticky and "ropey" (drawn out). Foulbrood also has a characteristic odor, and experienced beekeepers with a good sense of smell, 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. Some caps may be torn as well. Compare with healthy brood.
[edit] Treatment
AFB spores are present in virtually every hive. Weakened colonies can become diseased. Drugs, can boost the colonies defenses to the non-resistant disease pathogen. Chemical treatment of American foulbrood is possible using oxytetracycline hydrochloride (Terramycin). Another drug treatment is tylosin tartrate that was US Food and Drug Administration (FDA) approved in 2005.
Chemical treatment is sometimes used prophylactically, but this is a source of considerable controversy because the bacterium seems to be rapidly developing resistance.
Because of the persistence of the spores (which can survive up to 40 years), many State Apiary Inspectors require an AFB diseased hive to be burned. Other methods of containing the spread of disease are burning the frames and comb and thoroughly flame scorching the interior of the hive body, bottom board and covers. Dipping the hive parts in hot paraffin wax or a sodium hypochlorite solution (bleach) also renders the AFB spores innocuous.
[edit] European foulbrood (EFB)
Melissococcus pluton is a bacterium that infests the guts of bee larvae. European foulbrood is less deadly to a colony than is American foulbrood. Melissococcus pluton 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. An outbreak of the disease may be controlled chemically with oxytetracycline hydrochloride. Prophylatic treatments are not recommended as it leads to resistant bacteria.
[edit] Chalkbrood
Ascophaera apis is a fungal disease that 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 manageable 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.
[edit] Nosema
Nosema apis is a spore-forming parasite that invades the intestinal tracts of adult bees and causes nosema disease. Nosema is also associated with Black queen-cell virus. 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 (cleansing flights), they can develop dysentery.
Nosema is treated by increasing the ventilation through the hive. Some beekeepers will treat a hive with antibiotics.
Nosema can also be prevented or minimized by removing much of the honey from the beehive then feeding the bees on sugar water in the late fall. Sugar water made from refined sugar has lower ash content than flower nectar, reducing the risk of dysentery, and may have essentially the same nutritional content, although this remains a point of controversy among some beekeepers.
[edit] Dysentery
Dysentery is a condition resulting from a combination of long periods of inability to make cleansing flights (generally due to cold weather) and food stores which contain a high proportion of indigestible matter. As a bee's gut becomes engorged with feces that cannot be voided in flight as preferred by the bees, the bee voids within the hive. When enough bees do this the hive population rapidly collapses and death of the colony results. Dark honeys and honeydews have greater quantities of indigestible matter.
Occasional warm days in winter are critical for honey bee survival; dysentery problems increase in likelihood if there are periods of more than two or three weeks with temperatures below 50 degrees Fahrenheit. When cleansing flights are few, bees will often be forced out at times when the temperature is barely adequate for their wing muscles to function, and large quantities of bees may be seen dead in the snow around the hives.
Colonies that are found dead in spring from dysentery will have feces smeared over the frames and other hive parts.
In very cold areas of North America and Europe, where honeybees are kept in ventilated buildings during the coldest part of winter, no cleansing flights are possible, and all honey is removed from the hives and replaced with high fructose corn syrup which has nearly no indigestible matter.
[edit] Small hive beetle
Aethina tumida is a small, dark-colored beetle that lives in beehives.
Originally from Africa, the first discovery of small hive beetles in the western hemisphere occurred in the US. The first identified specimen was found in St. Lucie, FL in 1998. The earliest specimens confirmed since then were collected from Charleston, SC in 1996. By December 1999, small hive beetle has been reported in Iowa, Maine, Massachusetts, Minnesota, New Jersey, Ohio, Pennsylvania, and Wisconsin.
The life cycle of this beetle includes pupation in the ground outside of the hive. Controls to prevent ants from climbing into the hive are believed to also be effective against the hive beetle. Several beekeepers are experimenting with the use of diatomaceous earth around the hive as a way to disrupt the beetle's lifecycle. The diatoms abrade the insect's surface, causing them to dehydrate and die.
Several pesticides are currently used against the small hive beetle. The chemical is commonly applied inside the corrugations of a piece of cardboard. Standard corrugations are large enough that a small hive beetle will enter the cardboard through the end but small enough that honeybees can not enter (and thus are kept away from the pesticide).
[edit] Wax moths
Main article: Waxworm
Galleria mellonella (greater wax moths) will not attack the bees directly, but feed on the wax used by the bees to build their honeycomb. Their full development to adults requires access to used brood comb or brood cell cleanings — these contain protein essential for the larvae's development, in the form of brood coocoons.
The destruction of the comb will spill or contaminate stored honey and may kill bee larvae.
When honey supers are stored for the winter in a mild climate, or in heated storage, the wax moth larvae can destroy portions of the comb, even though they will not fully develop. Damaged comb may be scraped out and will be replaced by the bees. Wax moth larvae and eggs are killed by freezing, so storage in unheated sheds or barns in higher latitudes is the only control necessary.
Because wax moths can not survive a cold winter, they are usually not a problem for beekeepers in the northern U.S. or Canada, unless they survive winter in heated storage, or are brought from the south by purchase or migration of beekeepers. They thrive and spread most rapidly with temperatures above 90°F, so some areas with only occasional days that hot, rarely have a problem with wax moths.
[edit] Control and Treatment
A strong hive generally needs no treatment to control wax moths; the bees themselves will kill and clean out the moth larvae and webs. Wax moth larvae may fully develop in cell cleanings when such cleanings accumulate thickly where they are not accessible to the bees.
Wax moth development in comb is generally not a problem with top bar hives as unused combs are usually left in the hive during the winter. Since this type of hive is not used in severe wintering conditions, the bees will be able to patrol and inspect the unused comb.
Wax moths can be controlled chemically with naphthalene (mothballs) or paradichlorobenzene (urinal disks). If chemical methods are used the combs must be well aired out for several weeks before use. The use of naphthalene is discouraged because it accumulates in the wax. Control by physical means uses freezing of the comb.
[edit] Chilled brood
Chilled brood is not actually a disease but can be a result of mistreatment of the bees by the beekeeper. It also can be caused by a pesticide hit that primarily kills off the adult population, or by a sudden drop in temperature during rapid spring buildup. The brood must be kept warm at all times; nurse bees will cluster over the brood to keep it at the right temperature. When a beekeeper opens the hive (to inspect, remove honey, check the queen, or just to look) and prevents the nurse bees from clustering on the frame for too long, the brood can become chilled, deforming or even killing some of the bees.
To minimize the risk of chilled brood, open the hive on warm days and at the hottest part of the day (this is also the time when the most field bees will be out foraging and the number of bees in the hive will be at its lowest). Learn to inspect your hive as quickly as possible and put frames with brood back where the bees can cluster on it immediately.
[edit] Stonebrood
Stonebrood is a fungal disease caused by Aspergillus fumigatus. It causes mummification of the brood. Worker bees generally clean out the infected brood and the hive recovers.
[edit] Kashmir Bee Virus
Recently discovered, this virus is currently only positively identifiable by a laboratory test. Little is known about it yet.
[edit] Black Queen Cell Virus (BQCV)
As its name implies, BQCV causes the queen larva to turn black and die. It is thought to be associated with Nosema.
[edit] Pesticide losses
Honey bees are susceptible to many of the chemicals used for agricultural spraying of other insects and pests. Many pesticides are known to be toxic to bees. Because the bees forage up to several miles from the hive, they may fly into areas actively being sprayed by farmers or they may collect pollen from 'contaminated' flowers.
Carbamate pesticides, such as Sevin(R)-Carbaryl (C12H11NO2)can be especially pernicious since toxicity can take as long as two days to become effective; allowing infected pollen to be returned and distributed throughout the colony. Organophosphates and other insecticides are also known to kill honeybee clusters in treated areas.
Pesticide losses may be relatively easy to identify (large and sudden numbers of dead bees in front of the hive) or quite difficult, especially if the loss results from a gradual accumulation of pesticide brought in by the foraging bees. Quick acting pesticides may deprive the hive of its foragers, dropping them in the field before they can return home.
Insecticides that are toxic to bees have label directions that protect the bees from poisoning as they forage. To comply with the label, applicators must know where and when bees forage in the application area, and the length of residual activity of the pesticide.
Some pesticide authorities recommend, and some jurisdictions require, that notice of spraying be sent to all known beekeepers in the area so that they can seal the entrances to their hives and keep the bees inside until the pesticide has had a chance to disperse. This, however, does not solve all problems associated with spraying and the label instructions should be followed regardless of doing this. Sealing honey bees from flight on hot days can kill bees. Beekeeper notification does not offer any protection to bees, if the beekeeper cannot access them, or to wild native or feral honey bees. Thus beekeeper notification as the sole protection procedure does not really protect all the pollinators of the area, and is, in effect, a circumventing of the label requirements. Pesticide losses are a major factor in pollinator decline.
[edit] See also
| Honeybee types and characteristics (edit) | |||
| Queen bees | |||
|---|---|---|---|
| Worker and drone bees | |||
| Worker bee | Laying worker bee | Drone (bee) | |||
| Lifecycle | |||
| Beehive | Honeybee life cycle | Brood | Bee learning and communication | Swarming (honeybee) | |||
| Species and cultivation | |||
| Apiary | Beekeeping | Beeswax | Honey | Langstroth hive | Top-bar hive Apis mellifera mellifera | Africanized bee | Buckfast bee | Carniolan honeybee | Italian bee | Western honeybee |
|||
| Lists | |||
| List of honeybee articles | List of honeybee races | |||
| Diseases of the honeybee | |||
[edit] References and external links
- Canadian Honey Council Essential Oils for Varroa, Tracheal, AFB Control
- Sammataro, Diana; et al. The Beekeeper's Handbook
- Morse, Roger (editor) The ABC and XYZ of Beekeeping
