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July 24, 2002

Bagworms cases are approaching 3/4 inch long in central Illinois--large enough that control may be inconsistent with Bacillus thuringiensis kurstaki; and little control is likely with carbaryl (Sevin), diazinon, and several other insecticides. For later-season bag-worms, cyfluthrin (Tempo), trichlorfon (Dylox), spinosad (Conserve), or one of the other pyrethroids should provide excellent control.

Annual white grub eggs should all be laid, with hatching expected by the end of July in southern Illi-nois and early August in northern Illinois. Japanese beetle grubs hatch about the same time. Imidacloprid (Merit) and halofenozide (Mach 2) can be applied through the end of July to provide excellent control.

Green June beetle adults have been reported. These 1-inch-long, stout beetles have light green wing covers with yellow markings along the side. They fly during the day with reckless abandon--crashing into people, buildings, and everything else, and becoming a nuisance. The larvae look like other white grubs but are bigger, straighter and have short legs. They live on dried grass and other vegetation, being common in piles of grass clippings, livestock manure piles, and some lawns. Making the grass and manure piles into compost piles eliminates most larvae. Carbaryl (Sevin) watered into the turf controls the larvae in August and September. Other insecticides labeled for white grubs also provide control.

Twospotted spider mites are being found throughout Illinois, particularly on herbaceous perennials such as daylily and sunflower, as well as on shrubs and trees. Spider mites are susceptible to fungal attack in damp conditions, being able to become very numerous with low humidity and soil moisture. Probably, the dry weather in the last few weeks has been a major factor in this pest's buildup. Plants sprayed regularly with insecticides are also more susceptible to mite attacks. Insecticide kills off mite predators, allowing quicker buildup of mites. Several pesticides are effective against mites, including insecticidal soap, summer spray oil, abamectin (Avid), bifenthrin (Talstar), and hexythiazox (Hexygon). Usually two weekly applications are needed for control.

Peachtree borer flight is still heavy in northern Illinois, and insecticide application to control these insects attacking the base of purpleleaf plum, flowering cherry, and other Prunus should still be effective throughout the state. Permethrin (Astro, Ambush, Pounce) is recommended.

Author: Morton Arboretum Phil Nixon


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