Chicagoans, get ready for an extraordinary entomological event that last happened over 200 years ago: The emergence of the 13- and 17-year broods of periodical cicadas starting in May 2024. The two broods will only overlap in North Central Illinois.
These broods will result in billions of relatively harmless insects that will gather on and in trees. Here’s everything you need to know to maintain a healthy landscape amidst a once in a lifetime dual emergence of periodical cicadas.
The Cicada Phenomenon
Cicadas are unique insects known for their loud buzzing sounds and striking red eyes. These periodical cicadas belong to the insect genus Magicicada and are often identified by the “Brood” number. Periodical cicadas emerge in massive numbers after spending 17 or 13 years underground as juvenile nymphs. Once above ground, they shed their exoskeletons, the winged adults, known as imago, move toward higher ground such as trees and shrubs, they mate, and females lay eggs in tree branches before the imago die off.
Are Cicadas the Same as Locusts?
Some people are feeling nervous about this dual emergence because they believe that like locusts, periodical cicadas will consume plants and crops. This is simply not true. Cicadas belong to the insect Family Cicadidae while locusts are members of the Acrididae Family – so, the two insects are not even closely related. Furthermore, adult periodical cicadas do not consume large amounts of plant material or move in swarms as often the case with locusts.
When to Expect Them
The periodical cicada emergence in Chicago is expected to begin in mid-May, last 4-6 weeks, with its conclusion by the end of June. Exact timing depends on soil temperature—emergence begins when the top approximately 12” of soil reaches 64 degrees Fahrenheit.
What to Expect
The emergence of periodical cicadas is truly a wonder of the natural world, but it can also bring some horticultural challenges. Here’s what you can expect during this period:
- Loud Buzzing Sounds: Male cicadas produce loud mating calls to attract females, resulting in a cacophony of buzzing that can be quite intense, especially in areas with dense cicada populations (typically where there is a dense cluster of older trees).
- Tree Damage: Female cicadas lay their eggs in tree branches, which can cause minor damage to small branches. Mature trees typically are quick to recover from this damage while very young trees or newly planted tree whips may require protection. Remember: Most landscape trees are already 3-5 years old when installed, so while the tree may be new to you it is far from a truly “new” tree.
- Cicada Nymphs: Cicada eggs will hatch 6 to 10 weeks after they are laid. The tiny cicada nymphs will drop from tree branches to the ground and begin feeding on turfgrass roots. This feeding action does not cause serious damage to turfgrass. Over time, the nymphs will burrow 8-12 inches into the soil and feed on tree roots for the next 13 or 17 years. Like so much about the lifecycle of the periodical cicada, the underground feeding activity of these nymphs does not cause significant harm to plants.
- Increased Wildlife Activity: The abundance of cicadas will likely attract various wildlife, including birds, squirrels, and even pets. It is not uncommon to see this wildlife indulging in this season’s emergence. Again, such cicada consumption is typical and harmless.
How to Prepare
Periodical cicadas represent little issue to humans, wildlife, and pets. If you are concerned about damage to young trees in your landscape, here are a few recommendations to minimize any impact:
- Protect Young Trees: Cover very young trees and newly planted tree whips with fine netting to prevent cicadas from laying eggs in their branches, and surround the trunks with screening to prevent egg-laying. Use a breathable covering to minimize the risk of causing fungal or bacterial outbreaks resulting from excess moisture being trapped near tree leaves.
- Wait to Plant: If you are planting this spring, wait to plant young trees and tree whips Remember: Fall is a great season for tree planting as well.
- Avoid Chemical Control: Pesticides are generally ineffective against periodical cicadas, and spraying plants puts humans, pets, and wildlife at risk. Allowing nature to take its course is the best option.
Periodical cicada emergences are rare and awe-inspiring events that provide an educational opportunity to observe, appreciate, and be part of an amazing cycle of nature. This year’s emergence should remind us all of our connectedness and place in the natural world.
The Illinois Landscape Contractors Association and the Illinois Department of Agriculture have both provided educational resources that we encourage you to review and share with your family, in schools and workplaces, and remember when celebrating this phenomenon in your local community: ILCA Infographic + IDOA Frequently Asked Questions.
Are you ready to experience the buzz of the periodical cicada? Stay tuned for updates and share with us your cicada sightings on social media using #ChicagoCicadas. Together, let’s welcome these fascinating insects to our city with open arms!
Want to know more about ways your outdoor environment can be enjoyed by you, your family, and the urban wildlife with which we share our great city? Read about our approach to design: Genus Loci: Working With Your Environment