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Scouting Watch

June 12, 2002

Bagworms have hatched in central Illinois. They are about 1/4-inch long and still blowing from tree to tree. Treatment should be delayed for at least 2 weeks more in central Illinois. In southern Illinois, treatment can begin now, particularly if scouting shows feeding rather than ballooning. When ballooning, bagworms crawl to the top of the tree and drop on 2- to 3-foot silk strands. Treatment during this ballooning is ineffi-cient because it will probably be needed again later. Waiting allows control with one application.

Bronze birch borer should be treated now in north-ern Illinois. If dimethoate (Cygon) or imidacloprid (Merit, Pointer, Imicide) was used, only one treatment is needed. For permethrin (Astro, Ambush, Pounce), a second application after 2 to 3 weeks is suggested.

Black vine weevil adults are susceptible to insecticidal control during the first 2 weeks after emergence, when their ovaries are maturing. This corresponds to blooming of catalpa, which is occurring in southern and central Illinois and will soon occur farther north. Verify the existence of the weevils by looking for characteristic notching of leaf margins on yew, euonymus, rhododendron, and other hosts. Spray the foliage heavily, allowing runoff beneath the plant. Adults are on the foliage at night and hide in debris beneath the plant during the day. Acephate (Orthene), cyfluthrin (Tempo), and other insecticides are effective.

Euonymus scale crawlers should also be out in southern and central Illinois. They appear as tiny yel-low dots on the stems and foliage. Scout by wrapping black electricians' tape, sticky side out, on the stems. The crawlers get stuck on the tape and are easily seen against the black background. Many labeled insecticides are effective against these crawlers.

Author: Phil Nixon Bill Sullivan


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