COLONY COLLAPSE DISORDER
Colony collapse disorder (CCD), disorder affecting honeybee colonies that are characterized by sudden colony death, with a lack of healthy adult bees inside the hive. Although the cause is not known, researchers suspect that multiple factors may be involved. The disorder appears to affect adult bees’ ability to navigate. They leave the hive to find pollen and never return. Honey and pollen are usually present in the hive, and there is often evidence of recent brood rearing. In some cases the queen and a small number of survivor bees may remain in the brood nest. CCD is also characterized by delayed robbing of the honey in the dead colonies by other, healthy bee colonies in the immediate area, as well as slower than normal invasion by common pests, such as wax moths and small hive beetles. The disorder appears to affect only the European honeybee (Apis mellifera).
Through the years, U.S. beekeepers have faced obstacles to healthy bee management. Now, colony collapse disorder (CCD) threatens honey bees.
Since 2006, beekeepers have reported higher-than-normal colony losses, which are called colony collapse disorder.
Bee colonies affected by CCD can appear healthy, but then the adult bees disappear from the colonies.
Contain no adult bees, with few to no dead bees around the colony
Contain capped brood
Contain food stores that are not taken by neighboring bees or colony pests
Do not have enough bees to maintain colony brood
Have a workforce that consists of younger adult bees
Contain a queen
Are reluctant to eat food provided by the beekeeper
In past decades, colonies have died in connection with symptoms similar to those of CCD. These historic occurrences may not share a common cause with modern-day CCD, but they do share its symptoms.
The cause of CCD has not been determined, and every realistic cause remains a possibility. The following list of causes, which is not in a particular order, is not comprehensive—it may change based on new research.
For more detailed information about each possible cause, see the original publication, “Colony Collapse Disorder (CCD) in Honey Bees.”
Traditional bee pests and diseases.
While these are most likely not responsible for CCD— because they do not produce the symptoms—they may intensify the problem.
Hive management varies among beekeepers, but poor management can make any colony problem worse.
Queens affect genetic diversity and bee lineage. Across the nation, only a few breeder queens are used to produce queen bees (and therefore, all U.S. honey bees), which leads to poor genetic diversity.
Chemical use in bee colonies.
Chemicals used to treat bee diseases and pests have been found to have sub-lethal effects—even when used according to the label and management recommendations.
Chemical toxins in the environment.
Bees can be exposed to toxins while foraging, drinking contaminated water, or by inhaling them directly.
Varroa mites and associated pathogens.
Varroa mites remain the world’s most destructive honey bee killer. The mites, the viruses they transmit, and the chemical treatment they require are considered possible causes of CCD.
Malnutrition causes stress to bees, possibly weakening their immune systems.
Undiscovered or new pests and diseases.Unidentified or recently introduced pests and pathogens are considered possible causes of CCD.
Many scientists believe that CCD is caused by a combination of the above factors. This combination effect makes CCD more difficult to study.
WHAT DOES CCD MEAN FOR US?
Most people recognize the importance of honey bees and associate them with honey production. However, honey production is of minor importance compared to bees’ role in pollination.
EFFECTS ON INDUSTRY & CONSUMERS
Beekeepers who keep bees for pollination load their colonies on trucks and move them around the country to pollinate crops.
Growers pay beekeepers to bring honey bees to their fields to ensure adequate pollination of their crops. In return, the growers benefit through higher crop production per acre, larger size and better product shape, and even enhanced product taste.
US agriculture depends on honey bee pollination. No one expects bees to disappear altogether, but if bees continue to die at the current rates, we may experience increased food prices and decreased food availability.
SIGNS OF ENVIRONMENTAL PROBLEMS
Honey bees are biological indicators, meaning that honey bee health reflects the general health of the environment. Bee losses are possibly a symptom of a much greater environmental problem.
Although the causes of colony collapse disorder are not yet known, the following recommendations may provide beekeepers with some options:
Do not combine collapsing colonies with healthy ones.
If you find abandoned hive equipment, and the cause of bee death is suspicious, store the equipment so other bees cannot live in it. Do not reuse this equipment.
Use an integrated pest management (IPM) approach for varroa control in honey bee colonies. This will minimize bee exposure to potentially toxic chemicals.
Keep colonies strong by practicing best management practices.
CCD is believed to be complex and a result of multiple factors. One study evaluated 61 factors, and found that no single stressor stood out as the primary cause of CCD. However, colonies affected by CCD had more pathogens and more types of pathogens than colonies without CCD. Pathogens are disease-causing organisms. A group of stakeholders that gathered in 2012 found a similar consensus, that a complex group of stressors and pathogens are associated with CCD.
The Agricultural Research Service of the U.S. Department of Agriculture organized efforts to address the CCD crisis through surveys and data collection, samples analysis, and mitigation and preventive measures. A variety of possible causes of CCD were suggested. They included chemical contamination of colony food stores or beeswax; poisoning from pesticides, including nicotine-based insecticides known as neonicotinoids (the use of which has been restricted in some countries); possible lack of genetic diversity in colonies; and infection of colonies by pathogens or parasites, including known honeybee parasites such as the single-celled microsporidians (parasitic fungus) Nosema ceranae and N. apis and the invasive varroa mite (Varroa destructor).
Multiple studies have suggested that CCD might be the result of simultaneous exposure to a combination of two or more pathogens or stressors, in which the combination of stressors has a synergistic effect. Bee colonies are commonly found to be infested with pathogens and parasites, and the investigation of the interactions of all the possible causative agents has proved to be a challenge for bee researchers.
Pathogens that have been implicated in CCD include acute bee paralysis virus, Ascosphaera apis (chalkbrood disease), black queen cell virus, chronic bee paralysis virus, deformed wing virus, invertebrate iridescent virus, Israeli acute paralysis virus, Kashmir bee virus, Nosema species, Paenibacillus larvae (American foulbrood), and sacbrood virus. Many of those pathogens are present in increased abundance in hives affected by CCD, and varroa mites are capable of transmitting deadly honeybee viruses, including black queen cell virus and deformed wing virus. However, no pathogens have been found definitively to cause the disorder. Another parasite that may play a role in CCD is the phorid fly Apocephalus borealis. A known parasite of bumblebees, A. borealis has been identified as an emerging threat to honeybees. It was first reported to infect honeybees in 2012, when it was found to be associated with hive abandonment. Honeybees from parasitized hives often are infected with Nosema species and deformed wing virus. Many phorid larvae that emerge from dead bees also are infected with those pathogens, suggesting that phorid flies may serve as a reservoir for the agents, transmitting them to bees upon parasitization.