I think the decline in be number has a lot to do with poor pollination, I heard quite recently the bee populations are actually doing better in inner city areas as opposed to the country side.
bee hives are becoming a common sight now on high-rise rooftops and its apparently due to a richer diversity of plants grow in urban gardens.
Bees being the chief pollinators of apples, I'm sure must be having an impact on harvests.
Although apple varieties like Jonagold may be claimed to be "self fertile", they still do better it they can cross pollinate with different varieties near by, providing of course that the pollinator flowers at the same time.
Bees, I'm told can travel several miles between trees, but I guess it needs to abundant blossoms for it to be worth their while.
I've not tried hand pollination, but it may be interesting to experiment with, after all this is what plant breeders do, to develop new varieties, but I think you might be a busy little bee. :-)