how to get rid of yellow jacket nest underground ?
Typically yellow jackets have a single hole in the nest through which they enter and exit. They will all return to the nest for the evening, so the best treatment is to spray a hornet and wasp spray (which you can get just about anywhere they sell pesticides) directly into the hole right around sundown. Most sprays have a pretty strong stream and will travel 10 feet or more. The yellow jackets will die immediately after being sprayed. Soak the hole as thoroughly as possible for about 20-30 seconds. This will likely kill about 95% of the yellow jackets, so you may have to repeat the process the following evening to finish off any that survived.