Ground bees come in all shapes and sizes. Some are great in number and some live by themselves. Ground bees can incorporate wasps, bumble bees, yellow jackets, cicada killers, and digger wasps. Some are dangerous and some not so bad. So what's a person to do?
If you encounter a swarm of low flying black wasps or bees in your garden then you have an infestation of digger wasps or ground digging bees. They are not very aggressive and most cases you can walk through them without getting stung. As always, if you are or suspect that you are allergic then stay clear of all bees and wasps.
If you encounter large bees a few inches long then you have a case of cicada killers. Again, not very aggressive.
Yellow jackets and bumble bees can attack so be careful.
The best way to handle most of these ground bees is to dust their holes with a good insecticide dust. These dusts can be bought online at do it yourself pest control products stores. A good dust to look for is apicide, tempo, or delta dust. If dealing with yellow jackets or bumble bees use extreme caution, dust in the evening, or call a professional exterminator.