Colony collapse disorder

Colony collapse disorder (CCD) is a phenomenon that has been affecting both wild and domesticated honeybee hives in recent years. Scientific studies of the disorder have suggested that the probable causes are the spread of mite, viral, and parasite infestations such as the Varroa destructor mite, Israel acute paralysis virus, and parasitic infection by the fungus Nosema apis. It has also been suggested that other causes could be new diseases, pesticide poisoning through exposure to pesticides applied to crops or for in-hive insect or mite control, and climate change.

Neonicotinoids
Neonicotinoid and pyrethroid, two pesticides forbidden by USDA organic standards, have been tagged as potentially harmful to bee colony health and a possible contributing factor in colony collapse disorder. Organic and anti-GMO groups are known to blame pesticides used on GMO crops as a cause for CCD, but this overlooks the fact that organic farms use pesticides too, particularly ones known to have effects on bees. Pyrethrins, copper sulfate and Spinosad insecticides are approved for and used by organic farms, thus organic farms may also be contributing to CCD. The pyrethrum insecticide approved for use on organic farms is also highly toxic to bees. There is currently no clear link between any of them and CCD, but all have negative effects on bees.

In April of 2013, the EU implemented a 2-year ban on neonicotinoid (chemicals related to nicotine) pesticides which are suspected to be one of the leading factors in CCD. This didn't prevent CCD from hitting northern Europe and the UK a year later, though.

Feeding
Another suspected cause is the diet that beekeepers feed to their hives during the off season. During autumn and winter, bees naturally feed off of surplus honey that they have stored. However, because honey is the product that creates profits for beekeepers, they have traditionally taken the surplus honey and fed the bees with regular sugar. In recent years, however, as the price of high-fructose corn syrup has fallen below that of sugar, beekeepers have started feeding HFCS to their hives. Forcing bees to eat sugars other than their own honey may be a factor in their inability to survive certain pathogens and pesticides that they are regularly exposed to. HFCS can also break down into hydroxymethylfurfural if stored at high temperatures, which isn't toxic to humans but is deadly to bees; so if there were beekeepers who weren't careful about how their HFCS was stored and handled it could also contribute to bee deaths.

Big picture effect
Despite the appearance of CCD, the total number of beehives in the world has been on the increase: between 1995 and 2013, it increased from 66 million to 81 million. The decline in bee numbers in the U.S. actually occurred long before CCD was first observed, between 1945 and 1995; since 2007, the number of beehives grew by about 300,000. Therefore, although it is a serious problem that may ruin individual beekeepers, CCD is not currently a doomsday scenario for honey bees as a species.

Woo
A widespread belief persists that the spread of the disorder is due to either cell phone towers or GM crops. These beliefs are still clung to by hard greens, by those who believe cell phone signals pose a threat to health, and by conspiracy theorists who believe GMOs are part of a corporate conspiracy (usually attributed to Monsanto) to control the food supply.