Down the Garden Path
Richard Hentschel, Extension Educator
There has been some recent press covering cicadas in Illinois this summer. While we can have a few cicadas every year, the brood of concern will be invading northwestern Illinois in the summer of 2014. According to the experts that follow cicadas, this is known as the Iowa brood (also called the Marlatt's Brood III) and will emerge in most of the southern two thirds of Iowa. The brood will also get into Illinois covering about four counties.
When we do get our turn with a major brood 2024, the concern will be the same as homeowners west of here. After the cicadas emerge from their 13 or 17-year cycles of feeding on tree roots, they will be found climbing up tree trunks, shrubs and any other structure that affords them a place to change forms to become the flying singing cicadas we are familiar with already. We should feel lucky because only the males sing and once they have mated, they die. This leaves us the females which are the ones that as they lay their eggs, cause damage to our trees. The female cicada favors branches on the small side, around a quarter of an inch, while egg-laying damage can be found on branches far bigger.
For large trees, we see damage around the outer edges of the canopy where the branches are small. The female cicada cuts into the small branches where she lays her eggs. This typically will weaken that small branch and often results in that portion of the branch dying the next year, so you see "flagging" of young branches. Larger, older trees can tolerate this damage; it is the younger trees that have more of the favored branch diameters. On a young tree, much of the entire tree can be damaged. Some pro-active measures can be taken. When you hear the song of the cicada, it is time to take action. You can cover young trees with shade cloth, nylon screening, or a light fabric of your choosing works the best against the egg laying activity of the cicada. The protection should extend from the soil line up and tied tightly to the base of the tree.
You will know when it is safe to remove the covering, as you begin to see the females dead on the ground. The expert's note that the worst of the egg laying happens very close to where the cicadas emerge and diminishes very quickly the farther you move away from the emergence site.
As bothersome as the cicadas can be, there are no recommended control measures. The idea that they can survive years underground is quite astonishing really, so let them have their time in the sun because soon enough they will be underground for another 13 or 17 years!