In NJ there is a program where beekeepers can register their beeyard locations and pesticide applicators are required to check the lists and if there is a hive within a few miles distance they are supposed to notify the beekeeper in advance of spraying. I don't know how many do, though. The idea is that the beekeeper can then keep the bees boxed up for a day or two when spraying is being done. Many pesticides have residual effects for 3 to 7 days afterwards, though.
We spray a lot on our farm, pesticides, herbicides and fungicides. We try to do it in the evening when the bees are inside and try to keep overspray to a minimum. Also, we never spray anything that is in bloom. But we do have apple and pear trees located 60 or 70 feet from the front of the hives. When we spray them we get considerable drift of pesticide. So before we spray, in the evening after all the bees have returned to the hives, I cover the lot of them with a big blue plastic tarp that drapes down and lays across the ground on all sides. Then I leave it there after the spraying is done and remove the tarp the next morning. We also try to spray when the wind is still, or at least blowing the other way. The bees don't go to the trees because there are no blossoms, and the drift has settled. Oh, and we make sure the grass under and around the trees is cut so there are no blooming weeds that would take up the persticide for the bees to get.