Cottony maple scale has hatched in DuPage County in northeastern Illinois. These appear as gray specks on the leaves and stems. Many will be found along leaf veins, particularly on leaf undersides. Before spraying, check for twice-stabbed lady beetle larvae or adults. If these predators of the scale are numerous, insecticide use will be self-defeating.
Lecanium scale should be hatching in southern and central Illinois. A report during the week of June 12 indicated these insects were still in the egg stage. Sprays during the crawler stage or shortly after the reddish crawlers settle down should be effective.
Bagworms should be treated now. If the bags are over 1/2 inch long, use Bacillus thuringiensis kurstaki (Btk), trichlorfon, or a synthetic pyrethroid insecticide. Smaller larvae can be controlled with these and several other insecticides.
Peach tree borer adults are being picked up in pheromone traps at The Morton Arboretum. Treatment should be effective now in southern and central Illinois and can probably begin in about two weeks in northern Illinois. Peach tree borer attacks trees in the genus Prunus, such as flowering cherry and purpleleaf plum.