Friday, August 1, 2008

Pestering Cicada Killers

During the warmest days of summer, we will be joined by a rather large insect, known as the cicada killer. Cicada killers are active during late July and August, coinciding with the appearance of cicadas which they sting and paralyze. Cicadas are large insects that “sing” in the trees during late summer. The female cicada killer will search tree trunks and lower limbs for cicadas, which she will sting and drag back into her burrow.

The female cicada killers usually dig burrows in areas that are sandy, bare, and exposed to full sunlight. They prefer to nest in areas of little vegetation, compared to thick areas of turf. Each female captures at least one cicada (some collect two or three) and a single egg is laid in the cicada before being sealed off. Even though an area may contain many burrows, female cicada killers are solitary. This means that each female constructs a burrow and captures her own cicadas to serve as food for her developing young.

The cicada killer develop through complete metamorphosis, with four life stages: egg, larva, pupae and adult. In two to three days, the eggs will hatch. Depending on the number of cicadas in its burrow, the cicada killer larvae can feed for 4 to 10 days. Then the larvae will pupate and the adults will emerge from July to August. This insect only has one generation a year.

Adult cicada killers feed on flower nectar and sap. The female wasps are non-aggressive and rarely sting unless touched or disturbed. Male cicada killers are usually aggressive and tend to defend nesting sites. However males lack a stinger, so they are harmless.

Some Control Options

Non-Chemical Control Options:
1) Apply fertilizers and water turfgrass to promote growth.
2) Also place mulch in flowerbeds and around shrubs to cover sandy soil to help reduce cicada populations.

Chemical Control Options:
Control is usually not recommended, since this is considered a beneficial insect. However these wasps can become a problem in high traffic areas around homes and in commercial areas such as around swimming pools, flower beds, and golf course greens.

If control is necessary, first the nests should be located during the daylight hours, while the female is foraging. Then at night or before dawn, sprinkle a round 1 tablespoon of carbaryl dust into the burrow and then close the entrance of the burrow. Other suggestions for spray treatments that are labeled for wasp control include acephate, allethrin, cyfluthrin, cypermethrin, permethrin, and resmethrin. Repeat treatments may be needed for two to three weeks as new wasps move into the area.

Cicada killer, Sphecius speciosus (Hymenoptera: Sphecidae). Photo by Bart Drees, Professor and Extension Entomologist, Texas A&M University.