Mud wasps, or mud dauber wasps, construct their nests on the walls of homes, sheds, barns and other structures. At best, these nests are unsightly. At worst, they can damage equipment and stain walls. Despite all of this, you may want to think twice before you take action against mud wasps. They not like other wasps and are worth the small nuisance they might be causing.
Mud wasps are about an inch long and vary in color from dull black to iridescent blue-black. The name comes from the way they build their nests out of mud rather than paper like other wasps. Mud daubers roll mud into a ball and then mold it into place, creating finger-sized tubes along walls. Once completed, a wasp will lay a single egg into the nest and line it with insects. Once a nest is completed, the wasp moves on to repeat the procedure. It will not defend a nest once it completes one.
Mud dauber wasps are one of the few wasps you don’t want to repel, even when they are around your home. They are solitary, nonaggressive wasps that rarely sting, even to defend their nest. Instead, they use their stingers to immobilize flies, caterpillars, cicadas and spiders to put in their nests. One mud wasp, the iridescent-blue mud dauber (Chalybion californicum), is especially partial to black widow spiders. So, while mud wasps may a visual nuisance, they are getting rid of a less visible and more dangerous problem.
No effective means of repelling or preventing mud wasps from building their nests on a structure has been developed, according to entomologists at the University of Oklahoma. It is generally believed, but not scientifically proven, that mud wasps will not build under ceilings painted sky blue. If you do decide to paint, add an insecticidal paint additive to the paint for even more control. Screening vents, keeping garage and shed doors closed, and sealing crevices can also help prevent mud daubers from building nests in undesirable places.
Unlike other wasps, controlling mud wasps rarely requires the use of chemicals. You can kill adult wasps with a fly swatter if they become a nuisance. You can scrape wasp nests off of areas using a putty knife. Removing nests quickly and frequently may encourage wasps to use other locations. However, you may want to leave nests up whenever possible. The iridescent-blue mud dauber, known for killing black widow spiders, does not create its own. Instead, it uses abandoned nests created by other mud wasps.