A few years ago, another colony collapse occurred. Though it has happened more times than recorded history has been able to log, the concern was that new pesticides, which replaced the old pesticides blamed for the last colony collapse, might be the cause.
Since then, bees have rebounded nicely. The collapse was limited to one geography, rather than everywhere the newer pesticides - neonicotinoids - were used, so researchers have been scrambling to find out why it happened and therefore make it predictable.
A new study says it could just be stress - young bees are sometimes pressured to grow up too fast.