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
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)