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Periodical Cicada

June 3, 2003
Periodical cicada is set to emerge in the Chicago area and should do so by early June. Periodical cicadas feed for years as nymphs on the sap of roots of trees and shrubs. From central Illinois south, they emerge aboveground on the 13th year, molt into adults, and reproduce. From central Illinois north, they emerge on the 17th year. This year’s is an unusual emergence pattern that started in 1969, when part of the northern Illinois brood emerged after 13 years in northeastern Illinois instead of 17 years. Since then, this group of cicadas has emerged every 17 years, so there was an emergence in 1986 and will be one again this year. In 2007, northeastern Illinois will experience the rest of the emergence of this brood, along with most of the rest of the northern third of Illinois.

We expect the periodical cicadas to emerge through much of the Cook County suburbs, the eastern half of DuPage County, southeastern Lake County, and northeastern Will County. The expected emergence is a curved band running from Deerfield on the northeast, arcing to Addison and Lisle on the west and Crete on the southeast. The inside of the band arcs across northwestern, western, and southwestern Chicago.

Full-grown nymphs are brown, humpbacked, and about 3/4 inch long. They commonly construct soil chimneys that extend from the ground up to 3 inches high and are about 1/2 inch in diameter. These chimneys have been reported in the last part of May this year in the expected emergence area. Chimneys are not always constructed. Within a few days, nymphs break through the top of the chimneys or soil surface to crawl up trees, shrubs, and other upright objects, where they molt into adults. Adult periodical cicadas are about 1-1/4-inch-long, black insects with red eyes and orange-veined, clear wings.

Males produce a high-pitched wavering song that sounds like a trill when many are singing together. They sing primarily during the sunny part of the day to attract females to them for mating. The males and the singing die after a couple of weeks, while females remain alive for 2 to 4 weeks longer to lay eggs. Eggs are inserted into tree and shrub stems that are up to 2 inches in diameter. Heavy egg-laying causes twigs to break, resulting in dead leaves at the end of branches. Small trees may have enough eggs laid into the trunk that it breaks off.

Control is directed at preventing egg-laying damage, as adult feeding is insignificant. Although pyrethroids and carbaryl (Sevin) kill large numbers of adults, treated plants commonly experience about as much injury as untreated plants in landscapes and small planting areas. In nurseries and other large planting areas, repeated applications can reduce the damage significantly. Individual trees can be protected with nylon netting or wire screening tied around the trunk and larger branches. Make sure that the netting or screening stands out from the trunk so that the cicadas cannot reach the stem with their ovipositors. Although damage to small branches is obvious, its long-term effect is to make the plant bushier and is not usually worth control efforts.

Eggs hatch within a few weeks into small nymphs that drop to the ground and tunnel down to find a root to feed on. Over the years, nymphs commonly move to different roots but do not migrate very far. Nymphs have little effect on tree health, although studies have shown reduced diameter growth in trees during the 2 to 3 years before adult emergence. Because larger insects eat more than smaller ones, the older, larger nymphs apparently eat enough sap to reduce growth.

We are interested in tracking this emergence. I would appreciate knowing where these cicadas are found. Contact me by e-mail, pnixon@uiuc.edu; phone, (217)333-6650; or mail, S-408 Turner Hall, 1102 S. Goodwin, Urbana, IL 61801.

Author: Phil Nixon


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