Periodical cicadas have arrived

By John Fulton         

[May 24, 2007]  Even though Logan County is not in the heart of the territory of the periodical 17-year cicada, there will be spots experiencing the problem. There are two types of cicadas. The first is the "dog-day" cicada, which occurs in the heat of summer each year. The second is the periodical type that hatches in late May, based on soil temperatures, every 13 or 17 years. The 17-year brood is up this year, and numbers may be impressive in some areas.

The emergence line for the brood goes from northern Iroquois County to the Quad Cities, but does dip down into Sangamon County. That puts us in the range. If you can remember back 17 years ago, you might have some idea of how many cicadas you can expect. Prime areas would be heavily wooded for a period of many years. Numbers can average over 130,000 per acre.

The adult cicada is about 1 1/2 inches long, dark in color, and has red or orange eyes. The female uses an ovipositor, like a saw, to make slits in small twigs of trees. She then lays eggs in the slit. When the eggs hatch, the nymphs fall to the ground. They then tunnel in the ground, where they find a tree root to suck sap from for 13 or 17 years. The root feeding activities are not the most damaging, but the egg laying slits can cause severe damage to young trees.

Young transplants up to 2 1/2 inches in diameter can have their main trunk damaged to the point it will snap. On mature trees, there is little danger of the tree dying from the damage, but many branch ends will break off in windstorms. The favored twig or trunk sizes are three-sixteenths of an inch to 1 1/2 inches.

To protect young trees, or valuable small trees, a mechanical barrier is the most effective. Something like screen wire wrapped around the trunk will prevent damage. Insecticides will also kill many of the cicadas, but it takes only one female to do the damage. Sevin, permethrin or bifenthrin should show some effectiveness.

The other phenomenon that will occur is a great increase in traditional predator numbers, such as cicada killer wasps. These are extremely large wasps that paralyze the cicada, bury it in the ground and lay eggs in it. The insecticides mentioned previously will also be effective against the wasps. Remember, though, that the wasps are actually beneficial. Control should be done only in very high-traffic areas and children's play areas when the wasps become a hazard.

[Text from file received from John Fulton, University of Illinois Extension, Logan County Unit]