There are many ways to control stinging insects that nest in the ground, such as yellowjackets and bumble bees, but most are fairly “confrontational,” and the more time one spends interacting with a colony of stinging insects the greater the chances of getting stung.  One of the more effective and least confrontational methods is to use a disposable cup taped to a long stick to dump a tablespoon or so of insecticidal dust over the nest entrance and then just walk away and wait a day or two.  The bees or yellow jackets will track the insecticide into the nest as they come and go, eventually killing the colony.  Some of the more effective dusts to use for this treatment contain acephate (Ortho Fire Ant Killer  or Surrender Fire Ant Killer) or deltamethrin (Bengal UltraDust Fire Ant Killer, Terro Ant Dust or Delta Dust).
 
Before you can use this method you need to locate the nest entrance.  Spend time watching the insects come and go until you are sure you know where the entrance(s) is.  Of course, there is always a chance of getting stung when dealing with stinging insects.  You can reduce this by wearing protective equipment and/or by working at night.  Most stinging insects, including yellowjackets, are less likely to fly at night (European hornets are an exception), though they will fly toward a light if sufficiently agitated.  Set the light on some inanimate object so that it lights the entrance and then approach from some other angle to apply the dust.  So far, I have only used this method during the day and without protective clothing, by simply easing in from the side of the entrance (out of the flight path), dumping the insecticide over the entrance, and walking away before the insects sensed any disturbance.  So far it has worked beautifully, but there may come a day….; choose your own risk level.
 
Wait at least 24 hours before coming back to check for activity.  Usually there is none, but apply another treatment if you still see insects coming and going. In fact, it is a good idea to apply a second treatment anyway, just to be sure you have good kill.  Insects that are in the pupal stage when the nest is treated can continue to emerge for several days.  Bear this last point in mind if you decide to dig up the nest to see what it looks like inside.  It is surprising how many folks just have to see for themselves.  Better be really sure all the inhabitants are dead before attempting this.
 
Of course aerosol wasp and hornet sprays are also effective when used properly, and they can work faster.  These are the treatments to use when it is important to eliminate a nest as quickly as possible so that work or other activities can be resumed in the vicinity of the nest site.  But they are not quite as simple and non-confrontational as the insecticide dust treatment.