Honeybees have been declining for years, in part due to infestations of tracheal mites, which cause a dysentery-like disease in bees, and Varroa mites, which are external parasites.
Late in 2006, beekeepers noticed bees were leaving the hive and not returning. Larvae were present in the hives, but there were no adult worker bees to care for them. In all other bee disorders, there are dead bees in the hive that can be used to help determine the cause. Not with this new disease, called Colony Collapse Disorder. The bees simply disappear, as though they had lost their way and couldn’t find their way back to the hive.
Scientists have made only slight progress in determining the cause of Colony Collapse Disorder. Researchers at Penn State University have linked the disorder to the presence of Israeli acute paralysis virus. This new pathogen is a prime suspect in the disorder. However, it is not by itself the cause. Other factors, such as exposure of the bees to pesticides in the fields or treatment for mites, may make them more susceptible to infection with the virus. Unfortunately, U.S. beekeepers reported losses of 36% of their hives over the past winter. About a third of those losses were due to Colony Collapse Disorder.