Theories on Colony Collapse Disorder

A Brief History

Colony Collapse Disorder (CCD), is a phenomenon in which large numbers of adult worker bees simply abandon their hives, leaving them to collapse. It was first noticed by beekeepers during the winter months of 2006. Although winter losses are not uncommon to some degree, reports of 30 to 90 percent losses were suddenly being reported throughout the world. Some beekeepers lost most of their colonies, with the surviving few left almost too weak to pollinate or produce honey. In essence, it is the adult worker bees that are disappearing, leaving behind the queen and the young. Without the adults to provide food and maintain the hive, the colony will eventually collapse. Although reports of similar, limited occurrences go back as far as 1869, it is unknown if they are related to what we now call CCD. While beekeepers have been thus far able to meet the world’s pollination needs with the remaining colonies, CCD remains a potential threat to the pollination and agricultural industries.

Chemical Pesticides

One of many possible causes for CCD is the widespread use of pesticides in the agricultural industry. A survey in 2010 turned up evidence of up to 98 different pesticides and metabolites in samples of bee pollen. While there is evidence of negative effects upon the health and longevity of exposed bees, there is still no direct evidence linking any particular pesticide or combination of pesticides to CCD, itself. Another issue that makes it difficult to solely blame the use of pesticides is that many of the affected colonies are mobile, often traveling great distances over which they would be exposed to a wide variety of such chemicals. This variety makes it difficult to test for all possible pesticides at any one time. Bees are also known to store their pollen and honey, meaning that months could go by before any contaminates are fed to the rest of the colony. Thus, linking any actual pesticide exposure to the onset of symptoms is quite difficult.

Viruses, Disease, and Immunodeficiency

Sickness due to some unknown virus is another possibility currently being looked into. Viruses such as Acute Bee Paralysis and Deformed Wing Virus have been looked at as possible culprits. Both of these viruses are known to be carried by the Varroa mite. Interestingly, affliction with these mites has also been known to weaken bees’ immune systems. But while a good number of hives have been victims of these mites, they can’t be attributed to all cases of CCD. Israel Acute Paralysis Virus is another possible culprit often transmitted by the Varroa mite that has also been studied and a similar association has been found in a great many cases of CCD. But like the other viruses, it cannot be attributed to all known cases.

Deadly Fungi

Nosema Ceranae is a microsporidian fungus that has been known to wipe out entire bee colonies in the past within a matter of days. One theory that has been suggested is that beekeepers may have neglected to identify the symptoms associated with sickness from fungi such as Nosema and others. Fumagillin is an antifungal agent that has been used against Nosema Ceranae in the past, with positive results. Claims have also been made that some bee colonies were cured, due to its use. But although Nosema has been identified in a great many instances of CCD, it has also been found in healthy colonies. Because of the inconsistencies in these results, researchers today are more inclined to lean towards the possibility of a combination of both a virus or a fungi like Nosema and other stress factors working together.

Other Possible Causes

Among the other possible culprits that have drawn the attention of researchers are inadequate forage or poor nutrition, genetically modified crops, antibiotics and miticides used by beekeepers, changing weather patterns, scarcity of pollen or nectar, contaminated water, migratory stress, cell phones, and even electromagnetic radiation. Many of these, such as cell phones, have already been eliminated by most researchers as possible causes through past studies.

Recent Findings

In 2010, a group of biologists conducted another study using mass spectrometry techniques to identify various proteins in both collapsed, as well as healthy bee colonies. A virus known as Invertebrate Iridescent Virus, or IIV, was found to be present in 100 percent of the collapsed colonies, as well as some of the healthy ones. In addition to IIV, Nosema was found to be present also in the collapsed colonies, as well as some healthy ones. What drew the attention of researchers is that neither one of the two culprits could be solely blamed because the failing colonies all showed evidence of both IIV and Nosema, whereas bees that were infected by only one of these faired much better. While there is still reluctance in the scientific community to accept the findings of this one study as a final explanation for CCD, there is now a greater sense of hope that the ongoing research is finally on the right track and new colony management practices can now be developed to reduce future losses.

“Questions and Answers: Colony Collapse Disorder,” United States Department of Agriculture

“Colony collapse disorder – Wikipedia, the free encyclopedia,” Wikipedia, the free encyclopedia

“Honeybee colony collapse disorder | Pesticides | US EPA,” U.S. Environmental Protection Agency

Ian Douglas, “Study finds causes of Colony Collapse Disorder in bees – Telegraph,” The Telegraph

Jerry J. Bromenshenk, Colin B. Henderson, Charles H. Wick, et al.,”Iridovirus and Microsporidian Linked to Honey Bee Colony Decline,” PLoS ONE

“Colony Collapse Disorder, Bureau of Plant and Apiary Inspection, DPI – FDACS,” Florida Department of Agriculture & Consumer Services