EUREKA – Cicada Killers (Sphecius speciosus) are out and the inquiries at the Master Gardener plant clinics have been numerous, says Kelly Allsup, University of Illinois Extension Horticulture Educator. Cicada killers are solitary wasps that look like big black hornets with yellow banding on their abdomens appearing in late July and early August.

These insects are considered beneficial because they exert a form of biological control on the annual cicada (Tibicen spp.) population. The excavating and burrowing in open dry ground for nest construction can be a nuisance for most gardeners and homeowners. Cicada killers are considered non-aggressive. However, if you invade their territory a male may approach you to investigate and rule out that you are not another male cicada killer. The males are unable to sting. The females can sting but only when handled or disturbed because they lack the instinct to guard their nest like the honey bee.
The singing of the annual cicadas causes the adults to come above ground and out of hibernation. On their search for annual cicadas they will stop and drink nectar and water from your garden. Once the female cicada killer has found and paralyzed an annual cicada she will carry it back to her underground nest. The female places her prize in a nest cell, lays her eggs on it and seals up the cell. The larvae hatch in a few days and begin to feed upon the annual cicada before they form a cocoon to pupate for the winter and early spring.
University of Illinois Extension suggests planting ground covers and grass to avoid bare spots, add mulch and use irrigation to deter nesting around your home. It is highly discouraged to kill this beneficial insect unless safety of children and pets are an issue. An application of a carbamate based chemical product to the nest will kill cicada killer adults and their larvae. Please visit the Flowers, Fruits and Frass Horticulture blog at http://web.extension.illinois.edu/lmw/eb255/ for more garden insect information from the University of Illinois Extension office serving Livingston, McLean and Woodford Counties.