It has been about six months now since the initial media frenzy about Colony Collapse Disorder (CCD), hit the nation’s headlines. There has been lots of discussion, congressional testimony, and lots of speculation about the potential causes and consequences of dying honey bees.
 
For those of you who may not have heard about CCD, it is largely unknown problem that honey bee colonies have been experiencing where the entire adult population seemingly disappears. What is left behind in the hive is sometimes a small fist-sized cluster of young bees with the queen (but not always), a large area of brood (suggesting that the colony collapse occurs in a short time interval) and ample food stores of honey and pollen. For a single colony, this collection of symptoms may be curious but not all that alarming. When it happens to hundreds of colonies in the same area, at the same time, it means something strange is happening.

Given the honeybee's crucial importance to agriculture, scientists are hard at work trying to improve bee health. This year's devastation is worrisome in part because its cause is still unknown. In many hives, large numbers of adult bees simply disappeared without a trace, leaving larvae and pupae but no dead bodies to be examined for disease, pesticide residues or other agents. And, unfortunately, the list of factors that can afflict bees is long.

Parasites and diseases: These threats come from parasitic mites, especially Varroa mites, which live on the external surfaces of both larval and adult bees. Mites, as well as bacterial and fungal diseases, spread easily among bee colonies concentrated in a small area, such as is the case during pollination season in agricultural areas. Some of these diseases may have only infected European honey bees as a new host recently and/or only recently arrived in North America.

Other candidates that may be responsible include:
Environmental contaminants: possibilities include in-hive chemicals such as those used to control varroa mites, or agricultural insecticides that bees may encounter while foraging.

Nutritional stress: changes in how bees are managed, such as frequent transportation and placement near nutritionally poor crops.
 
Genetically modified crops: though questions about the insecticidal proteins are still asked, work completed prior to the current problem found little if any negative effects.
 
Lack of genetic diversity: there is evidence that the overall genetic pool for honey bees in the United States is not as deep as it once was. Reduced numbers of feral bees and lack of genetic diversity in commercial, mated queens may make colonies more vulnerable to disease.
 
Cool brood: researchers have shown that bees which develop at sub-optimal temperatures have difficulty learning and foraging. Chilled colonies may produce workers that fly from the hive and not return, a symptom that is similar to what happens with CCD. This is a new hypothesis that has yet to be considered, but should be testable.

edited by Phillip Glogoza
Regional Extension Educator - Crops