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Scouting Watch

June 14, 2002

Potato leafhoppers are common throughout the state. These elongate, 1/8-inch, green, jumping insects cause heavy damage to red maple, as well as injure sugar maple, redbud, wafer ash, and winged euonymus. Damage to red maple appears as malformed leaves with red, brown, black, and various shades of green mottling at the branch tips. The damage looks similar to that of 2,4-D and other phenoxy herbicides. On other hosts, the damage is much less evident, usually puckered leaves or early fall leaf color. In landscapes, treatment is normally not needed, but it is important to let clientele know that it is not herbicide injury. Treatment with pyrethroids is commonly used in nurseries because potato leafhopper feeding results in greatly reduced stem elongation and overall plant growth. Most pyrethroids provide control for about 2 weeks, but treatment is usually needed only monthly because it takes a couple of weeks more for leafhopper numbers to build up.

Bagworms have hatched in Illinois but are still ballooning from plant to plant in central Illinois. Treatment is appropriate in southern Illinois; it will be most effective through the end of June. Delay treatment in central Illinois until early July. If treatable infestations are found in northern Illinois, treat in mid-July.

Black vine weevil treatment should still be effective in northern Illinois. Reduced control will likely be seen in central and southern Illinois if treated now because eggs are probably already being laid. It only takes a few weeks of feeding for the females' ovaries to mature. However, treatment now should still reduce the amount of leaf-feeding by adults this year.

Earwigs are noticeable in central Illinois and should become so in about a week in northern Illinois. These insects are about 5/8 inch long, brown, and slender, with pincers on the back end. They hide during the day in cracks and crevices, being commonly found under loose bark, in mulches, and under door thresholds. When earwigs are found on a dead or dying tree, clientele may blame them for the tree's death. The earwigs are blameless; they are only taking advantage of the hiding place. Reducing bark mulch and fallen leaves next to the foundation, making sure that door thresholds fit tightly, and caulking cracks in the foundation reduce their numbers indoors. Permethrin sprays along the outside foundation also help keep them out. Earwigs will be present for about a month.

Author: Phil Nixon staff at The Morton Arboretum


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