Prof. Joseph R. Coelho, Dept. of Biology, Quincy University, Quincy, IL 62301
Female cicada killers can sting, but seldom do. After working closely with them since 1991, I have never been stung in the field. Note that I have netted them, put them in vials, dug up their burrows, grabbed them with pliers, and performed other unspeakable acts upon them with impunity. Most people are not interested in becoming that intimate with them. Unless you step barefoot on a female or grab her with bare hands, you are extremely unlikely to be stung. With just a little awareness, you should easily avoid being stung.
I had to grab one and hold it to my arm to be stung. It felt like the tiniest pin prick. A 1/4" painless white bump surrounded by a 1" red spot developed, but they went away within an hour. I have repeated this many times, and it's always the same. A graduate student volunteer had the exact same experience. (Note: some reliable sources differ with me on this point, describing intense pain. The question requires more research, but volunteers are not forthcoming. I suspect many of the reported painful cicada killer stings were actually delivered by European hornets, which they resemble, see above.) In spite of their large size, loud buzz and bright coloration, cicada killers are wimps. These effects are all part of their big bluff. If they sting you, they call their own bluff, so they avoid it as much as possible. I've tried to get them to bite me, too, but their mandibles cannot get a grip on my skin.
One caveat: for a susceptible (allergic) individual, a single hymenopteran sting may cause serious illness or death from shock. I had one alert reader e-mail an account of a severe allergic reaction. Such events are bound to be extremely rare.
Cicada killers belong to the family Sphecidae, all of which appear to have very weak stings. Their venom is adapted to paralyzing their insect prey, not to causing pain and damage to vertebrates. In comparison to other wasp, bee, and ant venoms, cicada killer venom has a relatively high LD50. In other words, it takes a lot of it to kill a mouse.
There is a scale of sting pain developed by biologists for rating the intensity of Hymenopteran stings. The scale ranges from 0 to 4. Although the scale does not allow for half-ranks, I'd rate the cicada killer a 0.5 (one half). Let's put that into perspective.
Let's take a broader perspective. Cicada killers only inhabit disturbed environments. Since humans have provided so much more habitat for them, there are probably more cicada killers now than ever before. Killing off a few will not drive the the species to extinction. Although I have argued that it's best to leave them alone, you needn't feel guilty about it if you have decided to get rid of your backyard population.
If you've read this far and still want to kill these animals, I have a few suggestions. The most natural and organic method would be to whack them--literally. Obtain a cheap tennis or badminton racket and swing away. Remember, there are always fewer than there appear to be. You'll be surprised at how rapidly your infestation becomes depleted.
The only published method of chemical control involves spraying pyrethroids down into the burrow entrance. This will kill the female, but not necessarily all her offspring because they are walled off in little chambers underground. To prevent an infestation in the following year, you'd have to spray the burrow early on, before many prey have been sequestered. You could probably also spray males while they are perching if you use one of those jet-squirting cans of "wasp and hornet killer," which are usually composed of pyrethroids. Several alert readers have informed me that such sprays have no effect, but one reports that starter fluid (available at automotive supply stores everywhere) is highly effective. Warning: starter fluid is highly flammable and will kill your grass on contact.
If your yard is infested and you want to stop them from nesting, there are no published remedies. I have some suggestions based on experience and science. Cicada killers inhabit disturbed environments; they require bare soil or very short grass in order to nest. These would be rare in a natural environment, but since we humans all have homes and yards, they are common. In fact, there are probably more cicada killers than ever because of the presence of modern human cultural practices. It should be possible to prevent their nesting by planting dense, tall vegetation. You could try mowing your lawn on the highest setting during the nesting period. In flower beds, try using a thick layer of wood chip mulch (that seems to have put them off of one of my field sites, but some respondents report that it does not work). One pest control professional mentions that a ground cotton hull mulch will stop the nesting. Cicada killers do not nest in hydric soils. Although wasting water is a crime, irrigate the infested area heavily (another good study site was destroyed this way, but, again, respondents' results have differed). I would appreciate feedback as to how well these work.
The following method was kindly submitted by alert reader Bill Nilsen: "I work for a company that does landscape maintenance for condominium associations, apartment complexes, H.O.A.'s, etc. We occasionally get requests to control cicada killers. I try to discourage it, but sometimes people insist on having it done. One technique I read about many years ago and tried seemed to work. However, it is rather labor intensive and, therefore, costly if you hire someone to do it. Because of the cost, I have only been requested to do it a couple of times during years when the populations seemed to boom. In the evening, after the cicada killers stop flying, you would sprinkle an insectide in a dust formulation around the areas where the holes are. You would then cover the area with a sheet of clear plastic. In the morning the cicada killers would come out & try to fly around. In the process, they would cover themselves with the dust. You had to make sure you took the plastic off before it got too hot & killed the grass. Although, after reading your article, it seems I was just killing the females. But since the females were no longer available, maybe the males left for better breeding grounds." I'm guessing the edges of the plastic would be weighted or held down somehow to prevent the wasps from escaping.
The following testimonial was provided (and reprinted with permission) by Deb Gendron. "I've had the giant wasps for about 5 years. They live in my front yard, mostly near the edge of the street. Last year the population of wasps became so large that my friends and relatives stopped coming over. I paid an exterminator to get rid of them and it didn't work. This year the mailman stopped delivering my mail because of the infestation. It was your information that helped me to gain confidence in controlling the population through (unfortunately) eliminating most of them. I must tell you that I spent about $30.00 in RAID, $60.00 in (something like) Diazinon, $45.00 in water and let's not forget the $125.00 for the exterminator. Guess what? It was all a big waste because the only thing that really killed them was to squash them. I figure that for the past 4 weeks the total of wasps that I've killed is at least 100 (way too many to inhabit my tiny 30x100 ft lawn). It is a daily and time-consuming mission. I compare it to trying to get rid of fleas in your carpet with flea powder and a vaccum. It's a one-wasp-at-a-time project. I'm hoping that by next year I'll maybe only have to kill 50 or 60 because I'm sure that some of them have already laid their eggs. I convinced my mailman to deliver my mail today; I'm going to print a copy of the information on your site and give it to him along with a tip$ from me for braving the wasps. It may sound kind of queer but I wouldn't have had the courage to handle this myself if it was't for your article. Thanks, Deb"
Finally, time is on your side. If you've tried all these suggestions and cannot get rid of your infestation, take heart. The wasps don't live very long, so at most you should have them only about two months out of the year.