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Plant Bugs

Ash plant bugs are active and feeding throughout the state, causing light spots on ash leaflets. This damage, along with additional stippling damage, will be present on the leaves throughout the summer.

Honeylocust plant bugs have hatched in southern and central Illinois and will soon hatch in northern Illinois. Be particularly watchful in northern Illinois because this insect caused heavy damage in that part of the state the last time we had a mild winter.

Both of these plant bugs are slender, flat-topped, long-legged insects that feed on the sap of leaves and stems. Honeylocust plant bugs are green and about 1/8 inch long as adults. Ash plant bugs are brownish and about 3/16 inch long as adults. Nymphs of both species are similarly colored and smaller.

Honeylocust plant bugs are present only in the spring. They feed on the expanding leaflets, causing them to be distorted and twisted. These leaflets usually stay on the tree, marring its appearance for the entire growing season. Heavy infestation will cause leaves to drop from the tree during June, but damaged trees will refoliate with undamaged leaves. As few as one nymph per compound leaf will cause obvious damage.

Control these plant bugs with synthetic pyrethroids such as bifenthrin (Talstar) or cyfluthrin (Tempo) or other labeled insecticides such as acephate (Orthene). Insecticidal soap is also effective.

(Other contributors to this article: staff at The Morton Arboretum)

Author: Fredric Miller Phil Nixon


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