Periodical cicadas will emerge this year throughout most of the southern two-thirds of the state. Emergence should begin in early June and last about three weeks. Outside Illinois, this emergence of the Great Southern Brood will cover most of Missouri, western Kentucky, and much of the southeastern United States north of Florida and south of Kentucky and Virginia. Very small trees may be subject to heavy damage by this insectís egg-laying activities.
Periodical cicadas occur in most areas of the eastern half of the United States. In the northern half of the country, these insects have a 17-year life cycle; those in the southern half have a 13-year life cycle. Rumors floating around the state suggest that 13- and 17-year emergences will coincide this year, which would cause very heavy damage. Letís set the record straight. First, only a single brood of 13-year cicadas is expected to emerge this year. Also, there is apparently only one region in North America where 13- and 17-year broods emerge in the same area--and that is in a small area near Clinton, Illinois.
Nymphs that hatch from eggs inserted into stems drop to the ground, burrow into the soil, and find a root to feed upon. The nymphs suck sap from the roots until the last year of their life cycle, when they emerge from the soil in the late spring, climb a tree, and emerge as adults. The adults are black, about 1-1/4 inches long, and have red eyes. They have clear wings with orange veins. The adults do little feeding, spending most of the daylight hours involved in reproductive activities. Male cicadas sing during the day to attract females. Mated females select twigs and branches up to one inch or more in diameter and insert their eggs into slits made with their ovipositors. Very little egg-laying occurs in the first ten days after emergence. Eggs are laid mostly during the last ten days of the female cicadaís adult life.
We anticipate emergence of the 13-year cicadas this year from Hancock and eastern McDonough counties south to Morgan, Sangamon, and Macon counties and also from Ford, southern Livingston, and western Iroquois counties south. The rest of southern Illinois is included in this 13-year brood emergence, except Iroquois, Vermilion, Edgar, Clark, Crawford, Lawrence, and Wabash counties on the east and Alexander, Pulaski, Massac, Union, Jackson, Perry, and southern Randolph counties in southern Illinois.
Periodical cicadas are a threat to small trees with trunk diameters of two inches and smaller. Their egg- laying may cause trunks and branches to snap off in windy conditions. Avoid planting very small trees before an emergence in areas where cicadas are likely to appear. Realize, though, that even in the regions listed above, some areas will have few cicadas or none at all. If an area has been cleared of trees and shrubs within the last few hundred years or was orig-inally prairie, periodical cicadas are unlikely to be present. These insects do not fly very far from where they emerge. That fact, combined with their long generation times, means that the spread of periodical cicadas is very slow.
Insecticides are only marginally effective against cicada, with carbaryl (Sevin), bifenthrin (Talstar), permethrin (Astro), lambda-cyhalothrin (Scimitar), and cyfluthrin (Tempo) providing only a small amount of control. Young trees with small trunks should be protected with hardware cloth, screening, or tree wrap during the few weeks that the adult periodical cicadas are present.