The great Cicada emergence is quickly approaching here in northern Illinois. This remarkable event occurs once every seventeen years (17 yrs.) 2007 was the last time Brood XIII (Brood 13), also known as the “Northern Illinois Brood” popped out of the ground in our area.
The term “brood” refers to the geographical area where different cicada species emerge. Some broods are small and emerge in limited areas. Others are very large and pop up across many states at about the same time. Regardless, there is a brood emerging somewhere every year. This spring will be an outstanding year for cicada emergence as both the 13-year and 17-year broods will emerge, bringing cicadas to most of Illinois during May and June. The central portion of the state (Springfield and south) will welcome Brood XIX of 13-year periodical cicadas. North of Springfield, including the Chicago region and far southern Wisconsin, will experience Brood XIII of 17-year cicadas. The emergence of these two broods rarely lines up in the same year, happening only every two hundred and twenty-one years (221 yrs)!
This event showcases the remarkable resilience and adaptability of these fascinating insects. These periodical cicadas have spent the past seventeen years (17 yrs.) in an underground nymphal stage. Contrary to what most believe, these cicadas do not spend their years underground in hibernation. Rather they are active, excavating tunnels and feeding on the sap from tree roots. As the soil temperature reaches around 64 degrees Fahrenheit, signaling the arrival of spring, these nymphs emerge in synchrony.
This phenomenon is natural and has been happening for centuries, but always seems to stir up excitement and wonderment during the years it occurs. Below is a short list of useful facts and recommendations to keep in mind during the period of cicada activity.
- This event does not last all summer. The cicadas will be here for only four to six weeks (4 – 6 wks.) The time of emergence is dependent on weather and soil temperature, anticipated to be sometime in May/early-June.
- Adult cicadas do not have much of an appetite and feed very little. The limited feeding is sucking sap from young twigs.
- The main damage Cicadas cause is to trees and shrubs by the adult female laying her eggs. The female cicada uses her long, knife-like ovipositor to make elongated slits to deposit her numerous eggs into small branches. The damage is limited mainly twigs and branches measuring one-eighth inch to just under one-half inch (1/8” – 7/16” dia.) The trunk will not be damaged. Smaller, younger trees and shrubs are more likely to suffer damage.
- The small twigs and branches that were a host to the cicada eggs may wilt and break off. With mature and healthy trees, the small branch tips will wilt later in the season, closer to August-September. High wind events often lead to branch breakage. This can occur the first year, or during the following year of cicada emergence. Consider this “natural pruning” and keep in mind, it is not harmful to the health of the tree or plant.
- A wide range of trees and shrubs can be used for the egg-laying process; cicadas are considered generalists. They do seem to favor certain trees which include apple, hickory, maple, and oaks. Birch, dogwood, walnut, willow, linden, and elms are candidates to be used as well. Additional plant material observed to host cicada eggs include rose, cotoneaster, forsythia, ginkgo, pear, and lilac.
- Conifer trees (cone-bearing) are not a preferred egg-laying host. Cicadas avoid plants whose sap or gum may prevent egg hatching. Other trees falling into this category include cherries, peaches, plum and persimmon.
- Chemical control (insecticides) is NOT recommended for control of cicadas. Not only have studies shown contact insecticides are not effective in controlling cicada populations, but they can be harmful to our beneficial insects which are necessary in keeping other insect and mite outbreaks in check throughout our growing season.
- Wounds resulting from the cicada egg laying typically are callused over by the tree within one to two years (1 – 2 yrs.) A handful of tree species may take at least three years (3 yrs.) to recover. Overall tree health, growing conditions, and level of injury all affect wound recovery rates.
- Planting trees and shrubs this year is an option. If you plan to plant small trees and shrubs during this year of cicada emergence, protective measures may want to be considered. Cover the branches of shrubs and canopies of small trees with fine netting, such as tulle, bird netting or insect netting during the egg-laying period. Mesh size should be no bigger than one-quarter inch (1/4” or smaller). Be sure there are no gaps in the netting and secure the netting to the trunk to prevent the cicadas from getting inside the covering. When securing the netting to the trunk, make it snug, but not so tight it will choke the tree; this is the time of the year when the tree trunk diameter is increasing in size. Whatever protective material is chosen, it needs to allow air and sunlight to get to the foliage of the plant and it needs to dry out after rain events. Avoid burlap, landscape fabric, frost covers and other solid fabrics. Wrapping material likely can be purchased from local hardware stores, fabric stores or purchased online.
Once the cicada emergence is complete, remove the netting.
Although the sound of the cicadas can be quite annoying and disruptive, and where cicada emergence occurs in high numbers may be off-putting for those that don’t like bugs, it is important to take some time to appreciate this rare phenomenon and recognize its ecological importance. The emergence is not only a visual spectacle but a fascinating interaction between cicadas and nature. The cicadas play a crucial role in nutrient cycling as they feed on xylem sap, and their exoskeletons they shed upon emergence contribute valuable nutrients back to the soil. In addition, their tunneling helps to aerate our soils. One intriguing aspect of the cicada emergence is the phenomenon of predator satiation. By emerging in such massive numbers, cicadas overwhelm their predators, ensuring that enough individuals survive to reproduce. While the noise of millions of cicadas may seem overwhelming, it is a festival of nature’s intricate design.
