The entrance to the nest was dug under a railroad tie. I could see the hornets going in and out pretty regularly. My first attempt was to wait until dark and then spray the entrance with one of those wasp killers that shoot 20 feet. I tried to spray right down the hole. Unfortunately the next day proved that the nest was not dead. There were fewer hornets, but they were still coming in and out. Tonight it rained, which I hoped would be additionally calming to the stinging bugs. I scraped everything away from the entrance. Then I used a foaming wasp killer which is supposed to coat a nest. I’d spray the entrance until it was buried in foam, then use a shovel to dig it out a bit. The force of the spray was sufficient to loosen up the dirt quite a bit. I repeated as often as I dared, which was until I’d almost emptied the can. I definitely dug into a hollow space underneath the wood, but I’m still not sure I got a clear shot at the nest. This is particularly true if the nest us up into the wood rather than even or below the entrance. I didn’t see any bugs, which I’d expect if I killed the heart of it. I’ll see if there is activity tomorrow. If there is, I’ll repeat this process. The location of the activity will help me know where to focus the next spray and dig attack.
The whole thing was pretty nerve wracking. I do not like to dig where I think there might be a hundred angry stinging insects. On the other hand, they would have had to wade through poisonous foam to get to me, so I was pretty safe. I will exterminate this nest. It just may take a few days.
My father’s trick for dealing with a wasps nest was a pint or so of liquid nitrogen from the lab. Pour into nest; leave overnight; excavate dead nest.
(When transporting liquid nitrogen use a Thermos flask, but replace the top with a plug of cotton wool – it lets evaporating gas escape.)
This is exactly the method I would use…if I had a lab with access to liquid nitrogen.