Scientists trying to figure out why so many bees are dying have not been able to find the single agent that would explain the deaths. In the past, widespread declines in bee populations were explained by pesticides, fungi, and parasites. This time, at least from what the scientists can see so far, the cause is simply stress. That is, it is a combination of factors making bees’ lives difficult, weakening their immune systems and making them susceptible to disease.
Researchers conducting autopsies of bees in declining hives are finding every disease known to bees. As one put it, “Their bodies are broken down and every little thing that comes into their system causes them problems.” Efforts to identify a disease that might be the primary cause of stress have been inconclusive. Instead, environmental studies of bees are providing clearer insight — indicating that the mysterious bee problems are largely the result of a stressful environment. For example, bees living near greenhouses are more likely to fall ill, apparently the result of one or more properties of greenhouses or their commercial bee populations.
Efforts to breed bees that are more disease-resistant are in the very early stages, but have not produced anything useful so far, and this also is consistent with the idea that it is not any specific disease, but an accumulation of stress, that is killing bees.
Winter is the toughest time for bees, as weather is unfavorable and there is little food for them for a few months, so it is the time of year when bee colonies are most likely to die off. The problems may be solved only when we can find ways to make things easier for bees, especially commercial bees, which seem to be having the worst problems. But that is the opposite of the way farmers are used to thinking about bees, so it is a change that may not come easily or quickly.