If you've been noticing increased activity of flying insects around your lawn or in your garden, chances are you have a case of sand bees or wasps. The two are often easily confused and labelled as one and the same. If they're bees, they might be bumble bees who have taken over an old burrow in the ground to build their hive and store honey. Wasps demand more caution, as some of them can be particularly aggressive. According to GardensAlive.com, if the insects are two inches long, they're most likely cicada killers--a non-aggressive wasp that hunts the ground-dwelling insects as food (see references 1). However, if they're less than an inch in length, you're probably dealing with the very aggressive yellowjacket. Whether they're bees or wasps, you should get rid of a ground hive if it's located near a home or a heavily trafficked area.
Gather a large amount of ice cubes or shavings (about a wheelbarrow's worth) and dump it down and on top of the entrance hole to an underground nest.
Cover the ice mound with a tarp or heavy plastic sheeting.
Weigh down the tarp or plastic sheet with bricks, plywood, or anything else heavy that will stop any surviving insects from escaping.
You can also eliminate sand bees or wasps by setting baited traps around the vicinity of the nest. Traps can be bought in most hardware stores. Put some old meat or fruit inside the trap to attract the insects. Another alternative is to use a bug zapper. Place the zapper near the entrance to the ground nest during the evening and turn it on. The bees or wasps will go out to attack the zapper and be killed. This works best with yellowjackets.
To be safe, approach the site of a ground nest on cool evenings. The insects will be resting inside, as it is harder for them to fly in cooler temperatures. Yellowjacket nests grow especially large in the late summer and should be approached with extreme caution. If the activity seems too intense, call in a professional to do the job.