First determine if they are nesting in the structure or just a large tree. If they are in the tree, do nothing. The aggressive bees flying about the yard will be the males but they have no stinger. If they are nesting in the structure, at night getting any type of insecticide into the chamber, be it liquid, aerosol or dust will kill them. Paint/re-paint or varnish exposed wood that they will like to nest in.
Most college departments of entomology can find someone to identify exactly the species of your problem bees. This info may be helpful if you plan to remove them yourself.
Some college departments have wild bee specialists who might be interested in removing the nest for their own research.
Optionally you can take a tennis raquet and bat the hovering ones out of the air. Then use regular wasp/bee spray on the areas of wood they they are interested in. Keeping old wood maintained and painted will discourage them in the long run.
Hopefully they don't remove your facia boards or fences for this purpose.
Carpenter bees attack my cedar soffit boards. They seem to like horizontal boards better than vertical. They are easy to recognize by the perfectly round 3/8" or so diameter holes they make.
The most effective treatment is to dust the holes with a powdered insecticide labeled for carpenter bees, like Drione. The bees carry the dust deep into the burrows where it kills all the bees. After a few days, plug the holes and then paint. Supposedly a good coat or two of paint will deter them, but I've not found it completely effective; they love that cedar.
Here is a place that sells a complete treatment kit; there are many others online.
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I plan to replace the soffit boards with PVC, painted to match the siding. That should be a long term solution.
This is what I did, so just sharing my experiences, not a how-to:
Found the holes and plugged them up. Didn't work, since they would drill new holes. My deck was becoming swiss chees.
Then I heard they rather use 'old' holes than redrill so I changed my attack. I filled the existing holes, sometimes occupied, with carpenter ant/bee powder. Then watched. The females would come out, dust covered and try to flee. The the males would jump on here and become poisoned and fall to the ground. Soon another female would check out the hole, become poisoned and fly away. Get rid of the females, then you have no hovering males.
Not a fan of poisons, but my son, then 4 years old, was attacked. A male went into a head butting session on him, and he refused to go out for a while.
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