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Scouting Report, 7/22/98

July 22, 1998

Mimosa webworm second generation is present in central Illinois, although damage is not yet heavy. Insecticide application now should prevent heavier damage later. Treatment should be made anywhere in the state where the damage is present.

Fall webworm is present throughout the state. This is the only generation in the northern half of Illinois and the second generation in the southern half of the state. Because the larvae stay within their silk tents throughout the day and night, your can eliminate the infestation by pruning off the silk tents. If you use insecticides, direct the spray at the silk tents using high pressure to penetrate the tents and reach the caterpillars inside.

True white grubs have caused heavy damage in northeastern Illinois. Much of the damage has been caused by raccoons stripping back the sod to feed on the grubs. Raccoon, skunk, and bird damage may result from as few as three to five grubs per square foot. Ten to twelve grubs per square foot are likely to eat enough roots to cause turf damage directly. Grub treatment decisions need to be made based not only on the likelihood of root damage but also on the likelihood of mammal or bird damage. If mammal or bird damage is occurring, a short-acting insecticide such as trichlorfon (Dylox) or bendiocarb (Turcam) will provide immediate results.

Dog-day or annual cicadas have emerged throughout Illinois. Residents in the southern half of the state still may be nervous from the periodical cicada emergence this spring. The cicadas present now are the larger, greenish ones, which are less numerous and rarely cause noticeable damage. Treatment is not normally recommended.

Katydids are also present in trees. The males of these insects are singers, with some species having a tendency to sit at the top of trees and sing from about 10 p.m. until 2 a.m. or later, which can be a real annoyance to people trying to sleep in second-floor bedrooms with the windows open. For others, like myself, the sound tends to lull them to sleep. These insects are green with long hind legs for jumping. They have long antennae and are two to three inches long as adults. One species has wide, leaflike wings, but others have long, narrow wings. These insects do not cause any important damage, although Iíve heard of entire trees being sprayed to kill the one katydid that was causing insomnia.

Author: Bruce Spangenberg Phil Nixon


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