Watch out for the cicada-killer!
Natural Resources Extension Agent
Forsyth County Cooperative Extension
It’s that time of year when you’ll see large numbers of huge cicada-killer wasps (nearly 2 inches) skimming around your yard, shrubs and trees. Many people are afraid of wasps in general and really large wasps, like cicada-killers, can be threatening. These wasps are erratic fliers that do not seem to notice humans are different than trees. If you watch them long enough you may see a male clumsily slam into the side of building.
What do they look like? Eastern cicada-killers have a rusty red head and thorax, amber-colored wings, and a black- and yellow-striped abdomen. Females are usually larger than males; cicada-killers range in size from 1 ¼ inches to 2 inches. Cicada-killers are most commonly confused with European hornets. European hornets are yellowish-orange colored insects almost an inch long, build large paper nests, are attracted to lights, and tend to occur in natural areas.
How dangerous are cicada-killer wasps? Cicada-killers are actually quite harmless. Usually the cicada-killers you see zooming around are the males, which cannot sting. A male stinger is a modified ovipositor (egg-laying organ); no male ants, bees, or wasps can sting. To be stung by a female cicada-killer you need to either step barefoot on her or grab her with bare hands.
Cicada-killers are present in the eastern U.S. from July – September. Cicada-killers, as their name implies, seek out cicadas or locusts. Cicadas damage deciduous trees (ex. maple, oak, birch) by laying eggs under the soft bark of new branch growth. Young cicadas drop to the ground, burrow, and spend the next couple years feeding on roots. Currently human attempts to control cicadas have not been practical or effective.
The cicada-killer males live for two weeks or so of intense patrolling, fighting and mating and then they die. Females live about four weeks, but they work even harder than the males, digging many burrows and hunting. In a typical season 100 female cicada-killers will clear over 16,000 cicadas from the surrounding area.
Cicada-killer females use their sting to paralyze cicadas to feed and rear their young. A cicada-killer grub will hatch from the egg in a few days, feed on the cicada and over-winter underground in a hard cocoon. It will hatch in early to mid July, dig its way to the surface and live above ground for 2-6 weeks; all adults die annually.
After emerging and mating, female wasps spend about two weeks searching for ideal areas to dig their u-shaped mound and burrows. Cicada-killers choose southeast facing, full sun areas with sparse vegetation, well-drained slopes and large deciduous trees nearby. They prefer sandy soils to loose clay in bare or grass covered banks, berms, hills, raised sidewalks, driveways and patio slabs. Some may nest under shrubs, in planters, window boxes, and flower beds, and occasionally in golf course sand traps. They do not nest in hydric soils.
How do you control them? The most economical control is to whack them with a badminton racket. Secondly you can irrigate the infested area. Try keeping the areas where they dig nests much wetter than usual – fill the burrows with water and wash away the piles of dirt surrounding them. This is a great reason for saving rainwater with a rain barrel.
You can also apply carbaryl (Sevin) or pyrethroids (ex. Advanced Lawn, Bug-B-Gone, Deltaguard, Scimitar, Talstar, Tempo) dust onto each nest entrance. Do not disturb the burrow as the female must walk through the dust to get a good dose. If there are more than 20 burrows in your lawn, it may be more practical to spray with the liquid version. Most likely you will need to repeat treatments for 2-3 weeks if new wasps move into the area. At close range, adults can be killed with a wasp aerosol as they light on foliage or enter the nest burrow. If you do not feel comfortable treating the area, contact a licensed pest control operator. Before using any insecticide, always read the label directions to confirm current listing of pests, and follow safety precautions.
Just remember that if you spray the burrows you will only kill the female, but not necessarily all her offspring since they are walled off in chambers underground. To prevent an infestation in the following year, you will need to spray the burrow early on, before many cicadas have been sequestered.
To help prevent cicada-killer nesting: plant dense, tall vegetation; mow your lawn on the highest setting during the nesting period; and in garden beds make sure you have a three-inch layer of hardwood mulch.
Finally, time is on your side. If you’ve tried all these suggestions and cannot get rid of the cicada-killers, be patient. The wasps don’t live very long, so at most they will be a pest about two months out of the year.
Managing Yard Pests is a principle of the Carolina Yards and Neighborhoods program. Contact the NC Cooperative Extension offices of Forsyth, Guilford, Davidson, Alamance and Randolph counties for a free copy of the Piedmont Yardstick Workbook. As you learn to incorporate these nine simple principles into your landscape, not only will you be able to manage vegetation more effectively and minimize the use of pesticides and fertilizers but you will save yourself time, energy and money in the process.
North Carolina Cooperative Extension
University of Kentucky
Prof. Chuck Holliday, Lafayette University, Easton, PA
Prof. Joseph R. Coelho, Quincy University, Quincy, IL