With 100's of theory's... the reality is that there a few common facts that disorientate BEE colonies. And it has been a fact by bee keepers for decades that higher levels of air pollution and pesticides have the highest impact on hive disruption.
Timothy H. Tear, "We know that ozone levels continue to be high and go well beyond EPA standards for public health," Tear said. "What's been pretty consistent is the more we look at air pollution's impacts on natural resources, the more we find those impacts to be."
Why we need to spend millions in further studies is very confusing... Bees are just the Canaries