I have come across a line of thinking that puts the blame squarly on Electro Mangentic Freq pollution, particulary ELF. Similar thing that causes dolphins and whales to un-explicably die.
The women that taught me this is rather learned, and instrumental in bringing awareness to the the european community on the pandora's box that is being opened as a result of us messing with ELF and EMP in general.
Killing off the bee's heralds changes afoot for the food chain. This is not good.