P&PDL Picture of the Week for
July 20, 2009

Cicada Killers: A Nuisance or a Danger?

Timothy Gibb and Terri Hoctor
Department of Entomology
Purdue University

A number of solitary bees and wasps reside in turfgrass and landscapes. Because of their ability to harm humans, these insects often evoke a great deal of anxiety. However, in reality they very rarely sting. Education is the single best strategy to help people deal with cicada killers.

Cicada killers are one of the largest wasps that burrow into the ground in this area.  At first glance, they are a very large, ominous looking wasp resembling a hornet or yellow jacket and evoke a good deal of fear. However, most of the wasps encountered are males, patrolling the nesting area. They may fly about, dive bomb, or even hover in front of, but they cannot sting people.

Females do not defend their burrows, and will sting only if handled. They are often mistaken for social wasps, particularly due to the fact that they nest in aggregations that may consist of a few to several hundred burrows. However, the cicada killer is a solitary wasp, not a social wasp, which means it is not associated with a large nest; in fact, typically there is only one individual in each nest or burrow.

Female cicada killers dig burrows in well drained, light textured soil, typically in an area with full sunlight. The 1½ inch diameter opening leads into an oblique tunnel that runs for 12-18 inches and reaches a depth of 6-10 inches. The female completes and stocks up to four cells, each containing from one to three paralyzed cicadas on which eggs are laid. When eggs hatch the larvae bore into and feed on the cicada. Secondary tunnels are often built off the primary tunnel; thus each female may rear up to 16 larvae in a burrow.

The larvae overwinter in their burrows, emerging the next July as adults. Between late July and mid August, these new adults emerge, mate and the female digs new soil burrows, stocks them with cicadas, and the cycle is repeated. Adults die by mid September. A large nesting aggregation results in unsightly mounds of soil that are characteristic of cicada killer activity.

Control of cicada killers is safely and most effectively done by placing a small amount of 5% carbaryl (Sevin) dust down into the soil tunnel. For a large nesting aggregation, the area can be sprayed. In both cases, the tunnel entrances should be left open.

 

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Cicada Killer

Purdue Plant & Pest Diagnostic Lab Purdue Cooperative Extension Service