Unless you find their nests completely intolerable, destroying highly beneficial dirt daubers isn't warranted. And if you don't like spiders, think twice before harming the daubers that adore them. (They particularly like black widows.) Sceliphron caementarium, solitary hunting wasps, don't congregate in paper nests or swarm like more dangerous wasps. They're not aggressive and rarely sting, unless they're handled. You can actually stand close by, unmolested, and observe interesting behavior as a busy dauber builds mud cocoons to lay her eggs in. Larvae hatch during the winter and feed on live spiders that their mother stuffs the chambers with before depositing the eggs.
Check for dirt dauber mud nests during the summer months, when adults are most active, if the nests' somewhat untidy appearance disturbs you. Look in warm, dry, protected areas, such as inside your garage or the undersides of your home's eaves. Try to catch them early in the season, before the mud cylinders are completely formed and egg-laying begins. The mud cylinders will still be open at this time, and if you chase the adults away while they're building, you won't be harming the potential young of highly beneficial insects.
Remove nests after dark, when adults have retired for the evening. Use a paint knife or wide putty knife to scrape the dried mud away. A healthy spray from a garden hose or pressure washer works well, too. If the nest is already sealed, live spiders might fall out of it as it crumbles. Don't worry; they've been paralyzed by the mother dauber and can't bite you. Live wasp larvae might fall out, too.
Treat the cleared area with insecticide if it makes you feel better, but there's really no reason to do so. Nothing has been proven to repel daubers from attractive areas. Besides, once the adult has finished laying her eggs and sealed the chambers with mud, her work there is done. She will leave immediately afterward, whether the nest remains intact or not. Daubers are unlike their more dangerous wasp relatives, which are highly territorial and aggressively guard nests and incubating eggs.
Repeat Steps 2 and 3 if you see returning dirt wasp construction if necessary. If you keep tearing the nests down as soon as they appear, daubers will often seek more peaceful nesting locations.