Cicada killers are, in fact, quite harmless. You can watch their antics for a long time. You can turn them into a lesson for your children. They're great subjects to photograph because you can get fairly close to them (a macro lens is still ideal). There's nothing more fascinating than seeing a female dragging a huge cicada to her burrow. So if you have them, enjoy them.
Cicada killers are most commonly confused with European hornets. Here is a really good European hornet web site. European hornets are introduced species that build large paper nests. The hornets are attracted to lights in large numbers, especially at night. They tend to occur in natural areas more than cicada killers, which like disturbed habitats. In the image below, a European hornet is on the left and a female cicada killer on the right (click to enlarge). The hornet is about an inch long, the cicada killer is an inch and one half. A male cicada killer would be about the same size as the hornet. Look carefully at the pattern on the back. Those of hornets have characteristic black tear-drop shapes (sorry for the poor image quality. Will try to upgrade later).
Other species easily confused with cicada killers (judging by how frequently I receive photos of them) are as follows: 1) horntails 2) great golden digger wasps 3) yellowjackets.
The most visible individuals are males, which cannot sting. A stinger is a modified ovipositor (egg-laying organ); therefore, no male ants, bees, or wasps can sting. Just 20 male cicada killers flying around an average-sized yard can seem like 100. In fact, a city park in central Illinois was closed in 1996 due to a major infestation. Another park in Florida was closed in 2007. Read article here. Males are about half the size of females, but otherwise hard to tell apart from them. They will even buzz and fake attempts to sting if you catch them. But they can't even break the skin with their false stinger. Although they may appear to be aggressive or chase you, they are probably just trying to orient themselves--you are a new, large object in their habitat. If you approach slowly and carefully you can get quite close to them while they perch. If you don't believe how harmless they are, check out Chuck Holliday's photo of a male perched on his finger. Few people believe me on this point, and everyone has an excuse to kill them--"I have kids," dogs, etc.
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 ¼"-diameter painless white bump surrounded by a 1"-diameter 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. I suspect that the few reported painful cicada killer stings were actually delivered by European hornets, which they resemble, or other mimics; 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 (actually, they've been moved to the Crabronidae now), 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.
Rank 0. No pain.Stinger unable to penetrate skin. Examples: Horntail, many ants.
Rank 1. Pain so slight as to cause no real deterrent.Examples: Sweat bee, sphecids such as the Great Golden Digger Wasp (Sphex ichneumoneus), many ants. Many people have been stung by sweat bees; a cicada killer hurts less.
Rank 2. Painful.Examples: Honey bees, yellowjackets, bumble bees, carpenter bees, hornets, most paper wasps. These are the most commonly encountered stingers, but their greatest danger is the potential for allergic reaction.
Rank 3. Sharply and seriously painful.More painful than a honeybee sting. Example: Velvet ant (Cow killer).
Rank 4. Traumatically painful, often medically serious.Examples: Tarantula hawk (Pepsis)--common in the American southwest. You will cry if stung. Bullet ant (Paraponera clavata): found in the American tropics. So painful you may fall to the ground, writhe and scream.
More on Justin Schmidt's sting pain index at Wikipedia.
Cicada killers may be considered turf grass pests for aesthetic reasons, but the effects of their burrows and dirt piles are short-lived, and will disappear with normal weathering. One reader recommends using a leaf blower to blast away the dirt piles. The digging may even provide aeration to the lawn. Although they often dig under and between the cracks of sidewalks, they probably don't move enough dirt to undermine them. The animals themselves are short-lived, and won't be around much more than a month.
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 (though I'm not sure about the western species). 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.
OK, muggles, if you've read this far and still want to kill these animals, I have a few suggestions. First, let me say that all the methods I know for killing cicada killers are here. I will no longer answer emails from those asking for my supposed "secret" method. 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. It takes some coordination, however. Modifications to this method include using a plastic baseball bat or a Racquet Zapper (electrified racquet). Other recent suggestions are to push them to the ground with a jet of water (set at about a 1" diameter) from a hose or a blast of air from a leaf blower and stomp them. A new trick is to leave a dead female on the ground, then kill the males that come over to check her out.
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. One alert reader claims success in killing flying adult cicada killers with Sysco (the nationwide quality food purveyors) Institutional Contact Insecticide, which produces a fog. The active ingredients are Pyrethrins, 0.04%; Piperonyl Butoxide, 2.00%. Sysco products are generally available to restaurants. Similar products are probably available from other insecticide manufacturers.
If your yard is infested and you want to stop them from nesting, there are few 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. Since we humans often have homes and yards, these conditions are common. In fact, there are probably more eastern 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. An excellent idea would be to plant a prairie. Or 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). An old remedy suggested by an alert reader was to wait until dark and pour boiling water down the burrow (avoid spilling it on yourself!). This method should kill the female, her larvae and pupae. I have also learned that diatomaceous earth can be a cheap and otherwise harmless insecticide. I think sprinkling it down the burrow would ultimately kill the female (by dehydration). Borax should act similarly, but it is NOT harmless. I'm told it's toxic to plants. 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 insecticide 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 method was kindly submitted by alert reader Brian Gwynne: "I have a labor intensive solution to suggest. In the early stages of emergence when the wasps are still young I staked out the burrowing areas with a can of SpectracidePRO Wasp and Hornet Killer in my hand, stalking them like a Navy Seal. Made for Spectrum Group, a division of United Industries Corp. (800-917-5438) SpectracidePRO has Tetramethrin (0.10%), Permethrin (0.25%), Pipernyl Butoxide (0.50%) and various carriers including petroleum distillates. ... A slight dusting doesn't seem to do much so you really have to dose the ones you hit. Knock them down with a decent hit then soak 'em. It killed the grass, true, but since this year the wasps decided to nest under and around our deck it was only a little grass and inconspicuous at that. After five days of stalking, spraying then leaving the area to let them emerge and gather again and repeating the process, I went through 8 cans at $3.95 per can. I wasted a lot of the stuff at first but my aim and anticipation of their flight patterns improved over time. I found that just before dusk, as the temperature has just started to dip and on very slightly breezy days when the wasps have a slight air current to fight, which slows them down and makes them occasionally fly in a stationary back and forth movement (sitting ducks) were the best times to launch the ambush.
...So for about a $30.00 investment there are only 3 or 4 of the buggers left....
I counted up the dead ones I could still find and they numbered 326. At roughly $.10 per wasp and a total of about 4 hours of work spread out over a week, I think this tactic was a success for this season."
Even with all these suggestions and possible methods, total control of cicada killers can be extremely difficult to achieve. Many correspondents have reported extreme frustration. 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 vacuum. 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 wasn't for your article. Thanks, Deb"
Another recent contributor paid an exterminator, which did not eliminate the wasps, then had to pay thousands to a veterinarian after her dogs got into the sprayed grass.
We have just learned of a highly effective way to get rid of cicada-killers in your lawn. The photo at left shows an area that had several thousand burrows (brown spots) in it last year. It was covered with six inches of crushed stone this spring (right) and the wasps have not returned.
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.
If you have read all available information (especially the "Life Cycle" page linked above), and still have comments or questions, IMPORTANT! EVERYTHING I know about how to kill cicada killers is here on this page. Really. I don't mind answering emails from people genuinely interested in cicada killers, but if I get one more asking for my secret method for killing them off, I'm going to scream!