Eastern tent caterpillar is very numerous in southern Illinois from I-70 south but is very uncommon so far in the northern two-thirds of the state. This pattern is a common one for this insect in Illinois; but usually, when it is numerous in southern Illinois, the rest of the state has at least a noticeable population. Although the caterpillars primarily attack trees and shrubs in the rose family, such as crabapple, hawthorn, wild black cherry, and pyracantha, they crawl to and feed on a wide variety of other plants once the caterpillars have stripped the foliage of the original host. Be watchful for feeding on birch, elm, maple, oak, poplar, willow, and other nearby trees. Large caterpillars may not be controlled very well by Bacillus thuringiensis kurstaki (Dipel, Thuricide), but spinosad (Conserve) and pyrethroids should be effective. Realize that fully grown caterpillars over 1-1/2 inches long are not likely to be controlled by anything other than a boot on concrete.
Honeylocust plant bug is present throughout the state. This insect is usually found in far northern Illinois only along the shore of Lake Michigan, but is being found this year at Morton Arboretum, so watch for it in other areas of northern Illinois as well. Acephate (Orthene), bifenthrin (Talstar), cyfluthrin (Tempo), and summer spray oil are effective controls.
Euonymus caterpillar has been found feeding at the Morton Arboretum on Euonymus obovatus. This 1-inch-long, whitish caterpillar with black spots feeds in groups on leaves inside of a web that they spin. It is most common on Euonymus europaea, being found in Illinois from about Kankakee on north. It is known to feed on Euonymus alatus (burning bush), but this has not been reported in Illinois. Euonymus caterpillar is controlled with a variety of insecticides, including Bacillus thuringiensis kurstaki (Dipel, Thuricide), as long as high-pressure spray is used to penetrate the silk web. Scout closely for this insect because it tends to cause heavy damage before it is noticed.