Last I saw was a suspicion that systemic insecticides could be to blame. I didn't read enough of it to see if they were even talking about what used to be called colony or hive collapse - also not sure when systemics gained widespread use - but it seems reasonable on the face of it that systemics might cause longterm effects.
My father kept several hives when I was a kid and I learned that: either bees aren't keen on the noise of yard equipment or they simply don't care for some people using it. That and I'm allergic to them.
We had some very nice days in April, here in the PNW. However, there are very few to none honey bees. Our fruit trees, hedges, and bushes should have been humming with wild bees but not a bee in sight. As a past commercial farmer-use pesticides conservatively, at the proper time, and in amounts less recommended. I will tell you that it is a awesome feeling to be in the cherry, apple, plum, orchard and feel the buzz of the bees working away flower to flower; Looking around in all directions nothing but the white of blossoms-DC Cherry Blossoms show was boring.
Your food supply is in endanger and unfortunately your Government is essentially powerless.