Colony Collapse Disorder (CCD) was first reported in 2006. Beekeepers began reporting high colony losses where the adult honeybees simply disappeared from the hives, almost all at the same time. There were few, if any, dead bees found in or around the hives. The queen and immature bees (brood) were often found in the hives with plenty of food stores, inadequately attended by a few adult bees.

CCD is believed to be complex and a result of multiple factors. One study evaluated 61 factors, and found that no single stressor stood out as the primary cause of CCD. However, colonies affected by CCD had more pathogens and more types of pathogens than colonies without CCD. Pathogens are disease-causing organisms. A group of stakeholders that gathered in 2012 found a similar consensus, that a complex group of stressors and pathogens are associated with CCD.

The study of CCD has improved scientists' understanding that one or multiple stressors can lead to colony loss. In addition to CCD, parasites and pathogens, poor nutrition, pesticide exposure, lack of genetic diversity, and habitat loss can weaken or kill honeybee colonies. The number of colonies reported to be lost to CCD has been declining since 2008, but overall colony loss rate is still a major concern. For the past eight years, about 30% of colonies have been lost each winter, but that number dropped to 23% in 2013-14. In 2013, surveyors attributed about 30% of colony losses to CCD, compared to 60% of colony losses in 2008.