Ground nesting bees are solitary and hence not aggressive and rarely sting. However, they do nest in groups, just because the soil/area is suitable for them to build their burrows--usually a bare spot in a lawn, etc. There are many different species of ground nesting bees, but their behavior is similar. Some species are happy to nest in bare level areas of soil, while others prefer to nest in the sides of dirt banks. Usually their activity is short-lived. Many species are only active for a few weeks each year, passing the inactive stages in the burrows/nest chambers dug by the females of the previous generation.
It is usually not worthwhile to worry about trying to control the bees-they usually disappear on their own after completing a generation or two. They will probably go away on their own by late spring to early summer. Also, these solitary bees are not aggressive and rarely sting-unless they accidentally fly up your pants leg, etc. And, these bees are important pollinators, so it is good to keep them around/tolerate them if possible.
The best way to obtain permanent control is to till the soil and amend or manage as necessary to get some grass or other ground cover established. Because these bees prefer to nest in areas where the soil is bare, or at least where grass is sparse, they will usually quit using a site once densely growing grass is established on it. On the other hand, once they find a spot they like, they will return year after year-unless something is done to make the spot unsuitable, as discussed above.
If you just have to kill the bees that are there now, you can do so by treating with Sevin (the ready-to-use Garden Tech product that comes in its own hose-end sprayer is an easy way to do so) according to the label directions for treating white grubs. Or you could use bifenthrin, Ortho sells a bifenthrin product that comes in a ready to use hose end sprayer. But, just spraying often provides incomplete control and it does not make the area unattractive to bees in future years.
