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Scouting Watch

June 29, 2005

Cottony maple scale crawlers have hatched throughout the northern half of Illinois. Crawler sprays will be effective at this time, including acephate (Orthene), bifenthrin (Talstar), cyfluthrin (Tempo), insecticidal soap, malathion, and summer oil. Before treating, check for the twice-stabbed lady beetle larvae and adults. Adults will be about 1/8-inch in diameter, round, black beetles with two red spots on the back. Their larvae will be up to about 3/16-inch long grayish-white, fuzzy blobs that move slowly on the branches and leaves. If this beetle is present in fairly large numbers, the crawler spray will probably kill no more scale than these insects would eat if they were not killed by the spray, and it will probably cause the scale infestation to last longer than if spray was not used. Of the suggested crawler sprays, insecticidal soap and summer oil will be less damaging to the lady beetles.

Bagworms have just hatched in northern Illinois, but they have been out in central and southern Illinois for about 3 weeks. It is time to spray in central and southern Illinois for these insects, but in northern Illinois wait until the end of the first week of July. This allows the bagworms to finish their blowing from tree to tree so that one instead of two sprays provides control. In central and southern Illinois, one application of Bacillus thuringiensis kurstaki (Dipel, Thuricide), cyfluthrin (Tempo), spinosad (Conserve), trichlorfon (Dylox), or Steinernema carpocapsae insecticidal nematodes should provide control at this time. Cyfluthrin is not labeled for use in nurseries.

Flea weevil adults are out feeding on Siberian and other elms in northeastern Illinois. These weevils will feed on the leaves for a while, eating holes in them, before seeking overwintering sites. Sprays of acephate (Orthene), imidacloprid (Merit), carbaryl (Sevin), cyfluthrin (Tempo), or other labeled pyrethroids will reduce the numbers that emerge to feed next spring. Earlier this spring, we recommended only acephate and imidacloprid because the systemic action of these insecticides would have provided control on the leaf-mining larvae as well as control the adults. At this time, there should be no more larvae this year, so the contact insecticides carbaryl and cyfluthrin that will kill only the adults can be used.

Author: Morton Arboretum Phil Nixon


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