Cicada Killer wasps are an eastern U.S. phenomenon, although out here in the western U.S. we enjoy some equally big wasps called Tarantula Hawks. They are not related, but all of these wasps, including the cicada killer, are "solitary" wasps that do not have a social colony. Instead, the female wasp creates a living chamber for her offspring, provides a stash of food in that chamber for her soon-to-be larva, and deposits an egg on it. She then seals the chamber, leaves, and does not return. Because of this these wasps have no instinct to protect a colony of queen and larvae, and stings by solitary wasps are extremely rare. Given the benefit we receive by their predation of cicadas or spiders or other insects the benefit far outweighs the risk in having them around.
The problems are there, though, and primarily it is a problem of educating the homeowners to understand what these wasps are and what they do. All the typical person knows it that it is an enormous wasp that "could" sting and therefore they want them eliminated. Killing these predatory wasp is actually counter-productive to the garden and the best protocol to have in place is to appreciate them and leave them alone. They will do their thing and be gone in a short time, as it usually is a single generation of these large wasps each year.
Another problem with cicada killers is the dirt piles they create while digging their tunnels and chambers in the soil. If this occurs in a nice lawn it disrupts the even appearance of that lawn and upsets the homeowner. In reality, that dirt pile can easily be raked flat and will disappear with the next watering. If the soil piles are on bare dirt areas there is no problem at all other than the fear the homeowner has for these large wasps, that may be nearly 2 inches long. Cicada killers specialize in cicadas, while many other kinds of solitary wasps go after crickets, grasshoppers, caterpillars, spiders, and other arthropods. The size of the populations likely coincides with the availability of food, so when lots of other insects are available the wasps can create larger populations of offspring. The hot weather in the U.S. this year seems to be leading to plenty of bugs.
While I understand that many people are "terrified of bugs" (a term I heard just yesterday) we should make the effort, at least, to educate them so they understand the benefits of most bugs in their landscape. We can dramatically reduce our unnecessary use of insecticides if we can avoid spraying for bugs that do not need to be killed. If you absolutely MUST try to eliminate these wasps on a property the most effective treatment is to directly spray or dust into the hole the female wasp is creating, and to do so after the sun goes down so you can be relatively sure the wasp is in that tunnel.
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Please note, Mr. Pest Control is answering questions supplied by PMP customers across North America. His answers are generated from industry and manufacturer-provided information. The answer may not be specific to the laws and regulations for your State, Province, Territory or Country. In addition, products mentioned may not be registered and or available in all areas. Always check with your local Univar office for specific information to your area. Always read and follow label directions.