The cicada killer is one of the largest wasps in the eastern United States, and its size alone tends to produce alarm. A wasp the length of a thumb, hovering low over a lawn or dive-bombing passers-by near a garden bed, is hard to ignore. But the cicada killer is a solitary wasp, and the behavior that looks aggressive is not directed at people. Understanding what it is and what it is actually doing explains why most sightings require no treatment at all.
Identification
Adult cicada killers are large, typically one and a quarter to one and a half inches long, with females running larger than males. The body is black and rust-red, with yellow banding on the abdomen that is similar in patterning to a yellowjacket but much more spread out. The thorax has rust-red or brownish-orange coloring. The wings are amber-tinted.
The size is the clearest distinction from yellowjackets and paper wasps. A cicada killer is substantially bigger than any yellowjacket. It is also much larger than a bald-faced hornet. The body shape is different too: cicada killers have a markedly narrowed waist and a long, tapered abdomen where yellowjackets look stockier.
Females are the ones doing the digging and hunting. Males are smaller and spend their time patrolling territories near the nesting area, investigating anything that moves. A male cicada killer may fly directly toward a person, hover, and appear threatening. Males have no stinger and pose no physical danger.
Behavior and Habitat
Cicada killers are solitary wasps, not social insects. Each female digs and provisions her own burrow independently. There is no colony, no queen, and no shared defense of a nest site. The apparent “colony” people sometimes describe is actually multiple individual females digging in the same area independently, because the soil conditions there are suitable.
Females prefer bare or sparsely vegetated, well-drained soil for their burrows. Sunny lawns with thin turf, sandy garden beds, landscape edges, packed soil near sidewalks and driveways, and slopes with exposed ground are all common locations. A female digs a burrow roughly ten to twenty inches deep using her mandibles and hind legs, kicking out a characteristic U-shaped mound of loose soil at the entrance.
Once the burrow is prepared, the female hunts cicadas. She stings the cicada to paralyze it and carries it back to the burrow, flying awkwardly with a prey item that may equal or exceed her own weight. The paralyzed cicada is placed in a brood cell along with an egg. The larva hatches and consumes the cicada as it develops. Adults feed on flower nectar and plant sap, not the cicadas themselves.
Adults emerge in late June or July depending on location, are active through August, and die off by September or October. The next generation overwinters in the burrow as a larva and pupates in spring.
Signs of an Infestation
The primary sign is the burrow entrance itself, a round hole roughly the diameter of a finger, surrounded by a crescent or fan-shaped mound of excavated soil. In soft or sandy soil the mound is loose and distinctive. In harder soil it may be less obvious.
Multiple burrows in close proximity are common when suitable soil conditions are concentrated in one area. A heavily dug area of a lawn or garden bed may have a dozen or more burrows. The soil disruption is the main practical problem: the excavated mounds are noticeable in a lawn, and repeated digging in the same area over a few weeks can produce visible damage to thin turf or disturb mulch beds.
Female activity is most visible in July and August during the nesting and hunting period. Adult flight is low and focused; females returning to the burrow often carry paralyzed cicadas, which is a confirming sighting if seen.
Health and Property Risks
The risk to people from cicada killers is very low. Males, which are responsible for most alarming behavior toward people, cannot sting at all. Females are capable of stinging but are focused entirely on their hunting and nesting activity and have no interest in people. A female cicada killer will not sting a person unless she is physically grabbed or handled roughly. The sting is reportedly painful if it does occur, as with most large wasps, but it is not medically significant for most people under normal circumstances.
People with documented venom allergies should maintain appropriate caution around any stinging insect, including cicada killers.
The damage to property is limited to the burrows themselves. The soil disruption is cosmetic rather than structural. Cicada killers do not damage building foundations, wood, or plant roots. The burrows do not create pathways for water damage. They are a lawn nuisance more than a genuine structural problem.
Treatment Options
For a small number of burrows in an out-of-the-way location, the most defensible option is no treatment. The wasps are active for six to ten weeks and then gone. The burrows do not persist as habitat for other pests in any meaningful way.
For a heavier concentration in a lawn or garden bed, or in an area with regular foot traffic, treatment is reasonable.
The most effective targeted treatment is applying an insecticide dust, such as a pyrethroid or carbaryl dust, directly into the burrow entrance at night, when the female is inside. Use a squeeze duster to apply the dust into the hole. The female contacts it on her next exit or entry and carries it deeper into the burrow as she moves. Seal the entrance afterward with soil tamped in place. Repeat for active burrows.
Liquid insecticide drenches poured into the entrance are also used. Pour slowly to allow the liquid to soak in rather than running off, then seal the entrance.
Surface sprays applied around the nesting area have limited effectiveness compared to direct burrow treatment. The key is getting product into the burrow where the wasp will contact it.
A professional can treat multiple burrows efficiently using commercial dust applicators, inspect the area for additional active sites, and advise on turf conditions that attract cicada killers in the first place. For a large yard with many active burrows, professional treatment is faster and more thorough than treating each hole individually by hand.
Prevention
The most effective long-term prevention is improving the ground conditions that attract cicada killers. They strongly prefer bare, dry, compacted, or sparsely vegetated soil. A dense, healthy lawn with good turf coverage is much less attractive for nesting than a patchy, thin one.
Overseed thin areas of the lawn in fall to improve coverage. Improve soil moisture through regular watering during dry periods, as cicada killers prefer drier, more compacted soil. Mulch garden beds thickly, at three to four inches, to cover exposed soil.
For areas where repeated annual nesting occurs, consider covering the soil surface with a dense ground cover, pavers, or landscape fabric under mulch. Eliminating the bare ground removes the nesting opportunity.
None of these changes eliminate the problem immediately, but they shift the habitat in a direction that cicada killers find less appealing over successive seasons.
What It Costs
Professional treatment of cicada killer burrows is usually priced per visit rather than per burrow, typically $100 to $200 for a yard-wide treatment during the active season. Multiple visits may be needed if new females continue to establish burrows during the season. DIY dust application materials cost $15 to $30 at a hardware store. Lawn improvement for prevention, overseeding and soil amendment, runs $50 to $200 in materials for an average yard.
When to Call a Professional
The honest answer is that most cicada killer situations do not require professional pest control. A handful of burrows in a back corner of the yard, away from where children play, are best left alone until the season ends.
Call a professional if burrows are concentrated in a high-traffic area, such as a play area or a frequently used garden path, if the number of active burrows is large enough that individual treatment is impractical, or if someone in the household has a venom allergy that makes having stinging insects in the yard a genuine medical concern.
See also: Yellowjackets, Wasps & Hornets, Mosquito.