Dave is right in his comments on spraying at night or late evening as being fairly safe to bees. The reason is that, as he says, most sprayed insecticides have a half life such that they will be fairly, but not completely, benign the next day. Also, since they are sprayed, their primary kill mechanism is contact. Bees gathering nectar will be minimally affected the next day as they will have little contact with what is left of the insecticide. The same for hives sprayed during the day. Foraging bees will be killed but the hive bees will be relatively safe, depending on the spray. But, if powder, and even worse encapsulated powder, is used, then it does not matter when the insecticide is applied. You will have bee kill. The reason is the bees do not die in the field but bring the encapsulated powder back to the hive as if it were pollen. Then the colony either dies or comes close to it. Sevin is often applied by backyard gardeners as a powder and is an efficient bee killer. But mix it with water and spray it and it loses most of its wallop since it sticks to leaves and is not easily, if at all, picked up by the bees. I like to keep my neighbors informed about Sevin and how it affects bees. I do not tell them not to use it, only how to use it, especially since I use it myself to combat cucumber beetles. I would be careful on imposing too stringent requirements on a grower. We ask them to read the label. So should we. Bill Truesdell Bath, ME