first get an exterminator out to saturate the house exterior and INSIDE the holes. once the bees are all dead and gone, fill the holes with wood putty and repaint. in some extreme cases you may may even have to replace a couple boards, but the posts are usually fine unless they have really been eat up.

Thanks. Sounds like good advice to me.

Wasp and bee spray won't even touch the darn things. I've sprayed it thick on them and then watched them fly off, but there is a spider spray that will kill the adult ones. I don't know if it works on the larvae they are laying in the holes. The only other method I know that works on the adults is to beat them with a fly swatter.

I had the same problem. Just this week I sprayed wasp spray directly in the holes at night. This killed them. When I sprayed them in the air, it didn't seem to phase them.

I have these things too! They just invaded my new cedar porch. They have eaten a perfectly round hole in the kneewall next to my steps, and you can hear it buzzing with life :(
I see that a previous post had recommended filling the hole with wood putty and repainting after they were sprayed with bug killer. Well, my porch hasn't been painted or stained yet though I was planning to stain it or seal it. Would this happen (bees invading/eating a hole in it) if the wood had been sealed?

Laura

Sevin dust in the holes will kill all the bees and larva in that hole within a few days. Then the hole can be plugged.

We spray them with a solution of water and dish soap. The soap suffocates them, and you don't have to worry about toxins. We have caulked some of our holes, and they ate through the caulk.