Perhaps the UK's carpenter bees are less damaging to structures than those in the US? Just as your nectar flow and "best" hive strength differ. The carpenter bees that have from time to time inhabited my deck make new tunnels each year, evidenced by the large sawdust piles under their holes in the spring. Since I was not poisoning the holes, that was not a cause of their tunneling. Left unchecked, they can seriously affect the integrity of a structure. However, it is only slightly more trouble to close up their holes when not in use and treat the wood to discourage their return -- they are welcome to tunnel tin any of the trees around, just not the railings that keep us from falling from the deck. In other locations, I've seen them become a real pest, buzzing people coming in and out of downstairs apartments. No real danger from the bees, but anxiety can cause it's own damage. Karen Oland -----Original Message----- From: Dave Green The stories about them "riddling" boards are from those who kept poisoning the holes so the bees had to drill new ones.