Are the leaves on your ash tree looking brown and curled? This may be the work of the ash plant bug. While they usually don't kill trees, infested trees look unsightly, grow more slowly and may exhibit dieback of small branches.

Adult plant bugs are slightly less than 1/4 inch long, varying in color from pale yellow marked with brown to almost black. They are extremely active insects which scurry undercover or fly away when disturbed. Because of their shyness and quickness, plant bugs are often overlooked, but their feeding damage always signals their presence.

Ash plant bugs are sucking insects which pierce plant tissue and feed on all liquids. Their saliva is toxic to the plant cells and a small area around each feeding puncture becomes white because of the loss of chlorophyll. Extensive damage causes brown, curled area on leaves which appear burned. To distinguish ash plant bug damage from various leaf diseases, look for the small varnish-like, brown or black excrement spots left on the underside of leaves.

They over winter as eggs on small twigs and branches. The eggs hatch shortly after the bugs open in the spring. Immature bugs start feeding immediately on new shoots, petioles and developing leaves. Within 3 - 4 weeks the insects mature, mate and begin laying eggs. These eggs hatch in 7 to 10 days. The second generation feeds from mid-summer until the first heavy frost.

Control of the ash plant bugs may be necessary for young trees or trees which have been weakened by repeat infestations. The insecticides Malathion, Sevin or Diazanon will give good control. If the leaves are rolled from insect feeding, a systemic insecticide such as Orthene will give better control. Other insecticides labeled for plant bugs such as Tempo can also be used. The active ingredient in Tempo is available in Bayer Advanced Garden Multi-Insect Killer.  When using insecticide, mix and apply according to label directions.

This page was last updated April 2003

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