Periodical cicadas should emerge in Vermilion, Clark, Edgar, and the northeastern portion of Champaign counties during the last week of May. Emergence will also occur at the same time throughout Indiana. Although the singing of the cicada males will be very noticeable, egg-laying damage to plants will not begin until about the middle of June; so there is still time to protect young trees. Loosely wrap the trunks of trees with trunk diameters of less than 1-1/2 inches with window screening or nylon netting to keep the insects from laying eggs into the trunk. Numerous twigs will be damaged on mature trees and shrubs, but no control is recommended as the damage is temporary.

Gypsy moth caterpillars are being treated during the third and fourth weeks of May in northeastern Illinois. This is part of the “Slow the Spread” program conducted by the Illinois Department of Agriculture and USDA–APHIS. Two treatments are applied, typically by helicopter, about one week apart to attempt local eradication of these insects. This is also an excellent time to treat to prevent damage in Lake County and other locations where this state and federal program is not treating gypsy moth infestations.

Lilac/ash borer male moth catches in pheromone traps at the Morton Arboretum in northeastern Illinois appear to be nearing their peak. Once peak moth catch occurs, treatment with permethrin is recommended 2 weeks later to obtain the most effective control of young larvae before they can enter the tree.

Euonymus scale crawlers and eastern tent caterpillar have also been found at the Morton Arboretum. So this is the time to control these two pests in northern Illinois.

Roseslug is feeding on roses throughout the state. These sawfly larvae are covered in their early larval stages with a slime that makes them look similar to slugs. They are usually 1/4 to 1/2 inch long. Young larvae eat through the epidermis and mesophyll of the leaf, leaving one epidermis intact that is initially whitish but soon turns brown. Older larvae eat holes through the leaves and feed from the edges. These insects are effectively controlled by acephate (Orthene), cyfluthrin (Tempo), permethrin (Astro), and other insecticides labeled for roses.