Issue 15, September 9, 2013

Potato Leafhopper

Potato leafhopper damage has become obvious during recent weeks. These leafhoppers attack oak, maple, red mulberry, red bud, cottonwood, birch, apple, dogwood, hawthorn, wafer ash, euonymus, black locust, and cherry.

Red maple is most severely damaged. The expanding leaves at branch tips are curled and stunted, and they are mottled with light green, red, and brown. Leaf edges and entire leaves may turn brown or black. Stem growth is greatly reduced. Overall, the damage looks similar to 2,4-D injury. Damage this fall is heaviest at the top of the tree rather than on side branches. On other host species, leaves may be misshapen, have brown areas, show early fall color, or have stippling (light dots).

Potato leafhopper damage to red maple.

Potato leafhopper adults are wedge-shaped, green, and about 1/8 inch long. They fly readily from foliage when approached and are very migratory, making it difficult to find the insects on damaged foliage. They are strongly attracted to lights at night and are small enough to go through the mesh of window screening. You'll probably recognize these pests as the little green bugs that fly around the newspaper or book you are trying to read during summer evenings indoors.

Potato leafhoppers

As nymphs, potato leafhoppers are similar in appearance to adults but are smaller and cannot fly. Even so, nymphs are quite active and will walk sideways to the other side of the leaf when it is inspected, making them difficult to see. Frequently, the only insect parts that can be found are the transparent, cast skins left behind by the molted nymphs.

Treatment at this time of year is probably not warranted. These insects start feeding in May in Illinois, and treatment at that time to prevent leaf damage and reduced growth through the growing season in nurseries is usually necessary. At this time of year, damage to landscape trees needs to be recognized for what it is rather than be misdiagnosed as herbicide or other injury. (Phil Nixon)

Phil Nixon

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