What caused colony collapse disorder, the abrupt disappearance of worker bees from managed hives reported at scale from 2006?
No single cause has been established despite nearly two decades of investigation. The leading candidates, Varroa mites and the viruses they carry, neonicotinoid and other pesticide exposures, poor nutrition from monoculture forage, pathogens such as Nosema, and interactions among all of these, each explain some collapses and fail to explain others, and the syndrome's defining sign, workers vanishing while brood and stores remain, resists a clean single-agent account.
What would resolve this Controlled studies able to reproduce the specific abandonment syndrome under defined combinations of stressors, or field epidemiology strong enough to assign relative weights to the candidate factors rather than merely listing them.
Entomology, Agroecology, ToxicologyColony Collapse Disorder (Wikipedia)