foiling carpenter bees

We've always had fat bees around. They don't bother anyone so I always told the kids to leave them alone- I knew they were great pollinators. They buzz around our deck in early spring and I assumed were looking for holes to lay their eggs. I thought this was one little hole per female bee, not a big deal.

Then one day I saw one bee atop another, with vigorous action. I'm used to seeing insects just sit still or the female crawling around while the male rides along, when they mate. So at first I thought they were fighting over a nesting site and one bee was attacking the other? I looked some stuff up and it turns out they were mating. Carpenter bees. Closer look and yep, the ones I've been seeing have the black shiny abdomen.

They don't just chew one hole. They gnaw extensive tunnels in old wood, laying rows and rows of larvae. After I knew what to look for I went around inspecting under our deck. I found over twenty holes, three or four which looked active- scatterings of sawdust underneath, and if I listened close I could hear them chewing. My husband thinks they haven't done any structural damage yet, but I know the colony has been here at least four years, if not longer, so.... they have to go.

This was my arsenal- tea tree oil and steel wool.

I put a tablespoon of tea tree oil with a cup of water in a spray bottle and doused all the areas with holes, three different times over the past five days. Actually, the first day I found the holes I stuffed them with citrus geranium leaves- supposedly the bees don't like any citrus scent- and sprayed lemon juice/water/veg oil mix. The bees just removed the leaves from some holes and kept at it. Tea tree oil is a lot stronger (in fact, the scent of it bothers me). Then I sprayed the tea tree oil and plugged all the holes I could with steel wool. They can't chew through that. We also played music outside, the speaker on the beam where the bees had their nest (they don't like vibrations apparently).

The number of bees I see hovering around the deck suddenly dropped from eight or ten, to three or four. These last few were really persistent. I could see fresh indentations near the plugged holes where they were trying to chew back in. I don't hear any more constant gnawing inside the wood though, or see fresh sawdust anymore. This morning I found a bee in my coldframe house, and I smashed it. Two more, their legs laden with pollen, kept coming back to the nest area. I felt kind of bad- they were just trying to return and feed their trapped larvae, probably. I waited until they landed on the beam and hit them with a towel. I killed three, the others haven't come back.

I feel rather bad about that- because I like pollinators- so I propped a few old, weathered boards in trees and shrubs on the other side of the garden, away from the house, hoping they might change quarters. Haven't seen any sign of that, though. (If that worked, can even relocate the entire colony, I've read- by carrying the board out into the woods in late fall/early winter when they bees are hibernating inside it. Leave it there and in spring they will wake up and live out there, instead of on your property).

Well. I think my nasturtium pot below the deck edge where the bee holes were, suffered a bit from my applications. Many of the leaves are suddenly speckled with yellow spots, I wonder if affected where the spray landed on them.