OK- bees. Some good advice thus far. Do not bother with spraying during the day. Most will be out foraging. Any social insects you want to deal with at night when nearly 100% will be on the nest. IIRC, bumble bees (I believe that is what you have based on description), are semi social. They are male and female live in single or multiple holes, but all females are reproductives (unlike termites, honeybees and ants where all the workers are sterile females). Powders like Sevin and other available powerdered insecticides work best. The first thing that bees do when you douse them with powder is fan their wings which aids in spreading the fine dust throughout the colony. A more environmentally friendly approach is to use smoke from sulphur which kills the bees and helps the tree, of course it is not nearly as effective.
Please be very careful with the allergies. If possible, you may have a beekeeper that can assist you with this. I am a beekeeper and have developed a near complete immunity to stings. Since they don't hurt as bad, a beekeeper may be willing to do the job for much cheaper. You provide the dust, the duster and the $100.00 and almost any beekeeper would come do it. We don't have that high of margins on pollination jobs and honey!
Good luck.
