Researchers have sifted through the list of possible Colony Collapse Disorder causes extensively during the past few years and haven't come up with one definitive answer. They have a few promising leads, however, and several factors yet to study.
At this point, the evidence seems to be leaning to the theory that CCD is caused by a couple of factors working in tandem. Here are some of the suspects who might share responsibility for Colony Collapse Disorder.
- Israeli acute paralysis virus (IAPV): This virus, first discovered by Israeli scientists in 2002, causes trembling, paralysis and death in bees. The virus has been found in many of the colonies abandoned by bees, but is also, on rare occasion, present in healthy colonies. As such, it's being considered a possible trigger or marker of CCD, but perhaps not its overriding cause. Recently, a study introduced IAPV into a healthy beehive that was enclosed in a greenhouse. Bees began dying within a week. Interestingly, researchers saw some of the functioning bees hauling the paralyzed bees out of the hive, as far away as the greenhouse would allow. The study's lead researcher said the results don't substantiate the theory that IAPV is the sole cause, but they do break promising ground.
- Neonicotinoid pesticides: These pesticides -- including clothianidin -- are neurotoxins used to protect crops against pests. But, these chemicals may also be harming helpful pollinators. The EPA has noted clothianidin as highly toxic to honeybees, and many beekeepers in Germany are blaming it for the massive die-off rates that struck their colonies in May 2008. Scientists say early results aren't conclusive; tests on the dead bees found fairly low-level traces of the pesticide in nearly every instance. In theory, however, the insecticide could paralyze the bees while they're out collecting nectar.
- Stress: Modern life may be more than some bees can handle. Researchers are looking to see if the pressures of being a 21st-century bee might be taking its toll. Many beekeepers are stretching the pollination season, giving their bees less time off to recuperate in the winter before hauling them to a new crop. Recent droughts can make finding an adequate amount of nectar a challenge for overworked foragers. These stressors, combined with factors like poor nutrition, could disrupt the bees' immune systems, making them more susceptible to disease.
- Varroa mites: These parasitic creatures suck the bees' blood, leaving open wounds that can then become infected. The mites deprive bees of nutrition, as well as open the door for other pathogens to enter. Varroa mites, as well as other nasty mites, pathogens and fungi, can invade a hive and give the bees a run for their money.
Other factors under the magnifying glass include the chance that other (possibly unknown) pathogens or microorganisms are involved, or that honeybees might be lacking in genetic diversity. Some people have proposed that genetically modified crops are to blame, but this idea isn't high on the list of likely causes. One theory -- that cell phone and cell tower radiation are the culprits -- has been ruled out.
While it seems like there's a perfect storm of dangerous elements descending on bees, what makes matters worse is that bee populations frequently come into contact with one another. Some beekeepers try to keep their colonies isolated from other hives during pollination events to prevent any dangerous exposure from ailing hives.
So now that we've looked at some of the factors that could be causing Colony Collapse Disorder, let's take a look at what's being done to find some answers.