you will have to spray into each of the holes to kill them AND basically paint your wood with insecticide. we had the same problem last year and the exterminator only charged about 80 bucks to kill them. after he was there i only saw 1 more bee, and that was only once.

you need to kill them and the larvae first, as woodpeckers will destroy the new wood to get to the larvae.

Are they perhaps German yellow jackets? You really need to find a way to make them gone!! I can tell more tales about them....their destruction and their nasty stings.....my son landed in the ER last summer with a bad reactrion to a huge amount of stings....never been stung before....but this was over the top!
Call a pro!
Linda C

Here is a link that might be useful: German yellow jacket wasps

I used wasp/hornet spray - the one that comes with a straw to spray through. I put the straw into the holes and sprayed.

I had dead bees falling on the patio for weeks afterwards - very rewarding.

We had them in a wall in our house years ago...they drove me nuts at night. We did not really know how to get rid of them...so hubby got a can of that expnding insulation foam and squirted it in the hole....smooshed them babies dead. When we took the siding off the following summer you could see where they were but no smell...worked for us.
Karen L