I am having an issue with them chewing on my wood deck, a couple snuck into my garage, and one started a hole on my wood trellis.
You can swat and stomp on the ones that you see getting in your face and crush them but that will not solve your problem. Those are most likely males. It is their job to run interference for the FEMALES, who are the ones busy boring tunnels into your wood to go deposit eggs. You can swat the females if you can catch them but they are only part of the problem. If this has been going on for awhile, they've probably excavated decent sized tunnels and deposited their eggs. Eventual the eggs hatch and the larvae mature into adult bugs that will come out to feed on pollen in August. Then they go back into the holes and hibernate there until next spring when they start a new mating and nesting cycle.
I sprayed WD40 in the holes and watched a bunch of them back out and die, but more kept coming. I had an exterminator come to my home and spray deltamethrin, an extremely popular insecticide that has become heavily used by exterminators for the last few years. It is safe for plants, animals, and humans, kills or repels a large variety of insects including carpenter bees, and when the liquid is formulated correctly it has a 90 day residual effect even against wind and rain. Then I was sitting there the other day at a gathering and I noticed the bees were back. They kept testing and probing the wood at various spots without drilling. The pesticide REPELLED them. However, because it was in liquid form it soaked into the wood. So even though they did not want to drill new holes in treated wood, they were not able to come in contact with the stuff and pick enough of it off the wood to kill them. Repelling them isn't good enough for me. My wood structures were not cheap to build and I do not want them looking like swiss cheese in a couple years, I want all of these things dead. Lesson: A liquid insecticide applied on wood surfaces will help prevent the damage, but will probably not kill them, and may redirect them to un-treated areas.
Further research showed that you absolutely have to squirt an insecticide specifically labeled or known to be effective on these things directly into the hole, as far as you possibly can. Everywhere I looked, SEVEN dust and DRIONE dust kept popping up as proven and effective options. A dust is recommended because it has a higher residual effect: If it is inside the holes it is protected from the elements such as rain and wind. And it will sit on top of the wood where it can come in contact with the bees rather than soaking into it where it becomes less effective. So what I did is I got a little handheld turkey-baster type-thingy with a tube on the end of it, and bought some SEVEN DUST from Home Depot. Then I went around jamming the tubes into the holes and puffing the dust in there. So now I have the liquid spray applied for a repellent and I have the SEVEN DUST inside the holes to kill the females who re-use them and the larvae in there.
For extra measure, I have two traps to use to catch any of the ones who avoid the poison.
This probably sounds like over-kill but I would rather this not become a multi-year battle where I helplessly watch my wood structures get eaten away to nothing. I hear when handled properly, the population dwindles within a couple weeks and it becomes much less of a problem in the following years. Time will tell.
