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Scouting Report, 8/12/98

August 12, 1998
Asian longhorned beetle stories are numerous in the news (see "Beetlemania 98" coverage on the Chicago Tribune Web site). You've probably been asked to identify more longhorned and other beetles than you wish. In addition to the original Ravenswood infestation in Chicago, beetles have been found in Wheeling, Addison, and Summit--all in northeastern Illinois. The Wheeling situation appears to be only a stray adult beetle find and probably does not indicate infestation. The Addison and Summit locations have infested trees, but the areas of infestation appear smaller than the Ravenswood location.

White grubs have hatched throughout the state. Scout irrigated turf and locations in turf where grubs have previously been a problem: Cut through the turf and pull it back to count the grubs in the root zone. Ten or more grubs per square foot will cause damage. Three or more per square foot may attract raccoons and skunks if they are numerous in the area. Damage will be more likely if nonirrigated turf was brownish in late June through early July. If grubs are numerous, use quick-acting insecticides such as trichlorfon (Dylox), bendiocarb (Turcam, Intercept), and diazinon.

Banded whitefly becomes numerous in flower beds this time of year. These 1/16-inch, white, gnat-like insects have grayish bands across the wings. They feed and build up on the field weed velvetleaf. Banded whiteflies tend to migrate to other plants as their numbers become massive and the velvetleaf starts to decline with the coming end of the season. A white fog of these insects will fly up from infested plants that are disturbed. Whiteflies sit on leaf undersides and feed by sucking out the sap. Heavy numbers can cause leaf distortion and brownish areas. Although the white, flying adults will feed on many plant species, the transparent, oval, 1/16-inch nymphs are usually found in high numbers only on the undersides of the leaves of velvetleaf and flowering maple, a close relative of velvetleaf. Feeding by even large numbers of the adults is unlikely to cause serious damage. Sprays of insecticidal soap or summer spray oil will provide control, if needed.

Fall webworm, yellow-necked caterpillars, and other caterpillars being found on trees and shrubs. Although these caterpillars may strip the leaves off fairly large branches, the branches will releaf next year. Damage of this type occurring late in the growing season does not seriously affect plant health. Various insecticides are effective, if needed.

Author: Phil Nixon


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