We have received several calls from people asking if periodical cicadas are due to emerge this year in Illinois. Marlatt's Brood XXIII, the Lower Mississippi River Valley Brood, is expected to emerge this year. This 13-year brood touches only small portions of Illinois, emerging in western Kentucky and Tennessee, southeastern Missouri, eastern Arkansas, most of Mississippi, and the eastern half of Louisiana. It is expected in southeastern Illinois in Crawford, Lawrence, and Wabash counties; in southwestern Illinois, in Alexander, Pulaski, Union, Jackson, southeastern Perry, and the western edges of Williamson, Johnson, and Massac counties. This brood should emerge in early to mid-May and be present for 4 to 6 weeks.

Adult cicadas insert their eggs through slits they make in stems up to 2 inches in diameter. In high-emergence areas, enough egg-laying occurs to weaken stems, causing them to wilt and snap in windy conditions. On established trees and shrubs, this causes aesthetic damage but no real threat to overall plant health. However, oviposition into trunks up to 2 inches in diameter can cause the trunk to snap off, severely damaging or killing young trees.

We recommend against planting small transplants the year before emergence to avoid damage. Trunks of susceptible trees can be wrapped or caged to reduce egg-laying damage. Emergence will not be heavy in housing developments and other areas where the trees and shrubs were removed within the past 50 to 100 years. Such activity kills the root systems and thus the cicada nymphs feeding on them. Periodical cicadas are slow to invade new areas, primarily because they get the chance only every 13 or 17 years when the adults are out.

Several insecticides are labeled and effective in killing large numbers of adults. However, in heavily infested areas, insecticide spraying causes little or no reduction in egg-laying damage.