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John Fulton


John Fulton
Former County Extension Director



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In The Backyard

Horticulture columns and tips done on a timely basis
periodical cicada

Periodical Cicadas

Posted by John Fulton -

The hatch is on. Even though Logan County is not in the heart of the 17 year cicada territory, there are spots experiencing large numbers. Here is a news release from Martha Smith, Horticulture Educator in Macomb, that discusses cicadas in depth.

Periodical Cicadas in Illinois, But Where?

The word is out.... 2007 is the year of the periodical cicadas! But not every area of the state will be inundated with these noisy insects.

There are two types of cicadas commonly found in large numbers in Illinois, explains Martha Smith, University of Illinois Extension horticulture educator.

Dogday or annual cicadas emerge every year from the soil during the heat of the summer. Dogday cicadas are green and approximately 1½ inches long. The male "sings" to attract females, usually in late afternoon and early evening. Females do not have sound-producing membranes like the males.

Periodical cicadas are different. In the northern half of Illinois, they emerge every 17 years. In the southern half of the state, they emerge every 13 years.

This spring, the Northern Illinois Brood XIII of the 17-year periodical cicada is expected to emerge north of a line from northern Iroquois County on the east, dipping southward to northern Sangamon County in the center of the state, and then rising northward to Moline and other Quad Cities on the west. These guys haven't been seen since 1990. This brood has a reputation for the largest emergence of cicadas known anywhere. On average, the emergence numbers could total more than 133,000 cicadas per acre. In the past, some emergences have had as many as 1.5 million cicadas per acre. The south will be spared until the Great Southern Brood XIX emerges in 2011.

"The timing of emergence is determined by soil temperatures," says Smith. "The northern emergence should begin late May."

The periodical cicada adult is 1½ inches long and dark brown/black with red/orange eyes. Males will "sing" to attract females. The trilling is very loud and occurs during the sunny part of the day. The mating period lasts for two weeks; then the males die, and the singing ends.

The female lays eggs using her ovipositor to make a slit in small twigs of trees. Branches between 3/16 of an inch up to 1½ inches are preferred. The eggs hatch, and nymphs fall to the ground and tunnel down through the soil to feed on sap in a root until they emerge 13 or 17 years later. Dogday Cicadas emerge on a faster lifecycle, anywhere between two to five years.

Smith says the root-feeding damage impacts growth but does not cause enough damage to justify control. The egg-laying slit made in the twig may cause the twig to dry and break off. This damage, too, is not harmful enough on an established tree to warrant trying to control these insects. The danger for young trees is when their trunk diameters are small enough that slits made in the trunk may result in the trunk breaking.

Research has shown that insecticide applications will kill cicadas; but when analyzing overall egg-slit trunk/twig damage, there is little difference between treated and untreated test plots. The only way to protect small trees from serious damage is to protect the trunk with screening or other material. Trunks larger than 2½ inches in diameter tolerate the egg laying.

Birds and other predators feed on dogday cicadas. One noticeable predator is the cicada killer. This large wasp catches the cicada, stings the insect to paralyze it, and then buries it in an underground chamber where it lays eggs in the paralyzed cicada. When the eggs hatch, the wasp larvae feed on the paralyzed cicada.

If historical records are true, Southern Illinois will only have the usual dogday cicadas this summer. Northern Illinoisans will once again need snow shovels to scoop up dead cicadas, and they'll need earplugs to block out the cacophony of male cicadas. Residents along the boundary will have to wait and see what emerges. For some, the mass emergence of cicadas is one of nature's many wonders. For others, it is a nuisance that leaves streets and sidewalks slick and smelly with rotting carcasses. For more information on cicadas in Illinois visit http://web.extension.uiuc.edu/cicadas/13or17year.html



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