Bienensterben

Colony Collapse Disorder (or CCD) is a honey bee disease, disorder or syndrome that describes the massive die-off affecting an entire colony. It is apparently limited to colonies of the Western honey bee in North America. The cause of the syndrome is not yet well understood and even the existence of this disorder remains disputed. CCD may be environmental, or may be caused by unknown pathogens or by mites or associated diseases. CCD is possibly linked to pesticide use though several studies have found no common environmental factors between unrelated outbreaks studied.

Limited occurrences resembling CCD have been documented as early as 1896, and this set of symptoms has in the past several decades been given many different names (disappearing disease, spring dwindle, May disease, autumn collapse, and fall dwindle disease). In none of the past appearances of this syndrome has anyone been able to determine its cause(s). Upon recognition that the syndrome does not seem to be seasonally-restricted, and that it may not be a "disease" in the standard sense (in that there may not be a specific causative agent), the syndrome was re-named.

From 1971 to 2006 approximately one half of the U.S. honey bee colonies have vanished, but this decline includes the cumulative losses from all factors such as urbanization, pesticide use, tracheal and Varroa mites and commercial beekeepers retiring and going out of business. The rate of attrition is alleged to have reached new proportions in the year 2006 and attribution has been made to the CCD phenomenon.

Phenomenology

The collapse of a colony of honey bees can be characterized by any one of the following:

• Complete absence of adult bees in colonies, with no or little build-up of dead bees in or in front of the colonies.
• Presence of capped brood in colonies.
• Presence of food stores, both honey and bee pollen:

i. which is not immediately robbed by other bees

ii. when attacked by hive pests such as wax moth and Small hive beetle, the attack is noticeably delayed.

Precursor symptoms that may arise before the final colony collapse are:

• Insufficient workforce to maintain the brood that is present
• Workforce seems to be made up of young adult bees
• Queen is uncharacteristically evident outside the hive
• The colony members are reluctant to consume provided feed, such as sugar syrup and protein supplement.

Possible causes

While the exact mechanisms of CCD are unknown, pathogens, pesticides or mite associations are suspected as causative agents. Whether any single factor is responsible, or a combination of factors (acting independently in different areas affected by CCD, or acting in tandem), is still unknown; it is likewise still uncertain whether this is a genuinely new phenomenon, as opposed to a known phenomenon that previously only had a minor impact.

• At present, the primary source of information, and presumed "lead" group investigating the phenomenon, is the Colony Collapse Disorder Working Group, based primarily at Penn State University. Their preliminary report pointed out some patterns, but drew no strong conclusions.

• One such pattern was that all producers in a preliminary survey noted a period of "extraordinary stress" affecting the colonies in question prior to the die-off, most commonly involving poor nutrition and/or drought; accordingly, there is at least some possibility that this phenomenon is correlated to nutritional stress, and may not manifest in healthy, well-nourished colonies.

• Some researchers have commented that the pathway of propagation functions in the manner of a contagious disease; however, there is some sentiment that the disorder may involve an immunosuppressive mechanism, not unlike the analog of HIV in humans, potentially linked to the aforementioned "stress" leading to a weakened immune system. Specifically, according to researchers at Penn State: "The magnitude of detected infectious agents in the adult bees suggests some type of immunosuppression." These researchers have further suggested a connection between Varroa destructor mite infestation and CCD, suggesting that a combination of these bee mites, deformed wing virus (which the mites transmit) and bacteria work together to suppress immunity and may be one cause of CCD. This research group is reported to be focusing on a search for possible viral, bacterial, or fungal pathogens which may be involved.

• Some researchers have attributed the syndrome to the practice of feeding high fructose corn syrup (HFCS) to supplement winter stores. The variability of HFCS may be relevant to the apparent inconsistencies of results. However, if this were the sole factor involved, this should also lead to the exclusive appearance of CCD in wintering colonies being fed HFCS, but many reports of CCD occur in other contexts, with beekeepers who do not use HFCS.

• Some have suggested that the syndrome may be an inability by beekeepers to correctly identify known diseases such as European foulbrood or Nosema. The testing and diagnosis of samples from affected colonies (already performed) makes this highly unlikely, as the symptoms are fairly well-known and differ from what is classified as CCD.

• One of the more common general hypotheses, pesticides (or, more technically, insecticides), is particularly difficult to evaluate for several reasons. First, the variety of pesticides in use makes it difficult to test for all possible pesticides simultaneously. Second, many commercial beekeeping operations are mobile, transporting hives over large geographic distances over the course of a season, potentially exposing the colonies to different pesticides at each location. Third, the bees themselves place pollen into long-term storage, effectively, meaning that there may be a delay of anywhere from days to months before contaminated provisions are fed to the colony, negating any attempts to associate the appearance of symptoms with the actual time at which exposure to pesticides occurred. To date, most of the evaluation of possible roles of pesticides have relied on the use of surveys submitted by beekeepers, but it seems likely that direct testing of samples from affected colonies will be needed, especially given the possible role of systemic insecticides (which are applied to the soil and taken up into the plant's tissues, including pollen and nectar), which might not be evident to a beekeeper.

• Most beekeepers affected by CCD report that they use antibiotics and miticides in their colonies, though the lack of uniformity as to which particular chemicals are used makes it seem unlikely that any single such chemical is involved. However, it is possible that not all such chemicals in use have been tested for possible effects on honey bees, and could therefore potentially be contributing to the CCD phenomenon.

• When a colony is dying, and there are other healthy colonies nearby (as is typical in a bee yard), those healthy colonies may enter the dying colony and rob its provisions for their own use. If the dying colony's provisions were contaminated by genuine infectious agents (such as American foulbrood), the resulting pattern (of healthy colonies becoming sick when in proximity to a dying colony) would suggest that of a contagious disease. However, it is often reported in CCD cases that provisions of dying colonies are not being robbed, suggesting that at least this particular factor is not involved in CCD.

It is unlikely that bee robbing spreads toxic insecticides. Pollen may well be contaminated in a dead or dying colony, because it is simply carried externally on the bees and stored away, but bees do not rob pollen. Honey does not become contaminated by pesticides used on bee forage, since the nectar is internally processed into honey, and a batch which is contaminated will end up in the honey stomachs of dead bees. Thus there is a natural protective mechanism to prevent honey contamination. This observation by beekeepers has been repeatedly confirmed by laboratory tests which frequently indicate toxic chemicals in pollen stores, but rarely in honey. Generally the only way honey can be contaminated by a manmade insectide is, if the finished product is exposed to a pesticides used by a beekeeper within the hives.

• Certain plant's nectars (and even some pollens) such as rhododendrons, azaleas, Passiflora, almond, aconites, hellebore, skunk cabbage, golden rain tree, Jessamine, Aloe littoralis and Chamaecrista fasciculata (Partridge-pea) are a few of the species known to be mildly toxic to poisonous to bees (and humans)Vorlage:Fact. Their poisons are known to include alkaloids, anthraquinones, grayanotoxin and andromedotoxin. The changing climate, range and other environmental factors are enabling more of some of these plant's nectars to potentially affect bees and other nectar gatherers.

• Potential effects of gathering pollen and nectar from genetically modified (GM) crops that produce Bacillus thuringiensis (Bt) toxin have not been investigated in great detail, but the primary crops involved (corn, and tobacco) are not preferred plants for honey bees (if they visit the plants, they typically do so when there is no other food available; they will gather only pollen from corn, and rarely visit tobacco blossoms). Cotton is highly subject to bee visitation for nectar, but there is little evidence of toxicity of GM cotton, other than that from insecticides used during bloom. Furthermore, the effect of Bt on insects is as a larvicide, whereas the CCD phenomenon involves the disappearance of the adult bees. It is therefore highly unlikely the syndrome is related in any way to GM crops.

Scale of the disorder

At least 22 different states as well as portions of Canada are known to have been affected by Colony Collapse Disorder. The disorder has been identified in a geographically diverse group of states including Georgia, Oklahoma, Pennsylvania, Wisconsin and California. In some states the loss of honey bee colonies is estimated as high as 75 percent of the population. The phenomenon is particularly important for crops such as the almond growing in California, where honey bees are the predominant pollinator and the crop value in 2006 was $US 1.5 billion. In 2000, the total U.S. crop value that was wholly dependent on the honey bee pollination was estimated to exceed $US 15 billion.

Honey bees are responsible for approximately one third of the United States crop pollination including such species as: almonds, peaches, soybeans, apples, pears, pumpkins, cucumbers, cherries, raspberries, blackberries and strawberries; many but not all of these plants can be (and often are) pollinated by other bees in the U.S., but typically not on a commercial scale. Most native pollinators cannot be utilized as easily or as effectively as honey bees, whose colonies can be moved from crop to crop as needed, and will visit many plants in large numbers. The commercial viability of these crops is therefore strongly tied to the beekeeping industry.

See also

• Bees and toxic chemicals
• Endangered arthropod
• Pesticide toxicity to bees
• Imidacloprid effects on bee population (This pesticide, while banned in France, has been rapidly increasing in usage in the USA)

External links

• John Finnerty, Agriculture: Disease Killing Bees, February 9, 2007
• February 5, 2007: NHB Funds Research for “Colony Collapse Disorder”