My first attempt at dealing with the yellow jacket nests failed. I tried two natural methods of killing off the nest, which you can read about here, neither of which worked. For a while I toyed with the idea of simply waiting it out, and letting the cold weather take care of the yellow jackets for me. In the end, however, we decided that we really needed to be able to get in that area of the garden and work, so that we could plant cover crops.
After considering a few more natural methods, I finally decided to go with something more potent. I ordered some Pyrethrin Dust, which is a botanical insecticide, made from crushed chrysanthemums. I had looked into Pyrethrin Dust before, but its fairly expensive, and I also had concerns about the dogs getting into it. I managed to find a company selling Pyrethrin Dust under a no longer used product name, Pyganic Dust, which I was able to purchase for quite a bit less than the same product labelled as Pyrethrin Dust, so decided to try it.
I've read mixed information regarding whether or not Pyrethrin Dust is harmful to pets. I didn't want to take any chances, so had Andrea feed Jack and Luke to keep them occupied while I applied the dust. I wore long sleeves and gloves, although I'm not sure that was entirely necessary. Again, however, I figured I should play it safe. Applying the dust was very simple, I just poured a bit down the hole and applied some extra around the opening. With that done I just had to wait and see if the product was effective.
After a few days I went back over to the garden and checked for yellow jacket activity. I didn't see any flying out of the holes, but wanted to be a bit more certain. I poked a long stick around the opening, and eventually into the holes, with no reaction. Finally I pounded on the ground near the opening, in hopes that the vibration would cause any remaining yellow jackets to show themselves. When this didn't cause any reaction either I decided that the job was done.
I've been back over there working a couple of times since then and haven't seen any more of the yellow jackets. At this point I'm satisfied that they have been dealt with. I would have preferred finding a more natural method of dealing with the problem. However, I feel like the Pyrethrin Dust was a good compromise between completely natural methods and some of the more toxic methods I've seen suggested such as using a bug bomb, or the very common suggestion of pouring gasoline down the hole. I still have plenty of the dust left, so will likely be using it again next year.