Colony collapse disorder (CCD) is a baffling detrimental condition in colonies of honeybees (Apis mellifera). It is characterized by a rapid loss of the adult bee population, with an absence of dead bees in and around affected colonies. No single cause of CCD has been identified, but numerous stressors, including compromised immune function, viral pathogens, and exposure to pesticides and insecticides (in particular, neonicotinoids), have been proposed as probable causes. Since the initial description of CCD in 2006, this disorder has resulted in significant reductions in the numbers of adult honeybees, which are the predominant pollinators of numerous economically important plants and crops. The decreases in honeybee populations explicitly due to CCD continued until at least 2015. However, entomologists are now noticing that the threat assigned to CCD seems to be decreasing dramatically. Some researchers even believe that CCD, as a specific phenomenon or disorder, has vanished (although it may be in a dormant state). Overall, bee colonies are still suffering losses, but researchers are less concerned about CCD and have shifted their attention to the general health of bees, trying to determine how nutrition, pesticides, pathogens, and parasites are affecting bee populations. See also: Colony collapse disorder; Economic entomology; Hymenoptera; Insect diseases; Insecticide; Parasitology; Pathogen; Pesticide; Pollination; Population ecology
The variableness of CCD has been troublesome for investigators studying the disorder. Previous attempts to pinpoint the cause of CCD to one specific culprit (or a combination of specific culprits) have been futile. The only common thread across all the cases of CCD was the absence of dead bee bodies near their hives. It is possible that a type of social behavior (based on a common evolved response to disease prevention in insect societies) occurred so that the infected bees would not pass on CCD to other members of their colony. See also: Social insects
Despite the possible elimination of CCD as a categorical cause of bee deaths, beekeepers remain vigilant against any or all of the aforementioned stressors affecting bee health. Under ideal conditions, beekeepers would prefer to lose less than 15–20% of their colony numbers to various ailments. However, even with the threat from CCD being diminished, beekeepers are suffering losses (due to other factors) of approximately 30–40%. This is less, though, than the situation in 2012 and 2013, when annual losses hovered near 45%. See also: Agricultural science (animal); Beekeeping