Get ready -- 17-year cicadas preparing to emerge in northern Illinois

Some people may have noticed cicada-like creatures in the ground while gardening or after flipping over a log recently.

That’s because the brood of cicadas that emerge from the ground every 17 years in northern Illinois is preparing to make its appearance in the coming weeks.

The nymphs — the immature stage of life in which cicadas spend about 17 years underground — are beginning to dig tunnels to reach the ground’s surface.

“They are preparing to emerge. I have not seen any reports, nor have I myself seen any adults yet; the soil is not warm enough yet for that,” said Negin Almassi, a resource management training specialist with the Cook County Forest Preserve. The periodical cicadas should appear once the soil reaches 64 degrees, which is expected by late May.

“It’s a fun wait-and-see game right now to see when the firsts start to emerge, so they’re getting ready, and they generally do that about three weeks before they start coming out,” Almassi said.

Months after the 17-year cicadas have come and gone, people across northern Illinois will again hear the buzzing of the male annual cicadas that fill trees in the area in the late summer every year. The annual cicadas, which arrive in August and September, aren’t expected to overlap with the 17-year cicadas.

In central and southern Illinois, another breeding group of cicadas that arrive every 13 years are expected to emerge in the next couple of weeks. Some areas of central Illinois could see a mix of the 13-year and 17-year cicadas — a phenomenon not seen in 221 years.

Almassi, who helps run the forest preserve’s singing insect monitoring program, is heading a forest preserve initiative for this year’s cicada event to encourage people to record videos of cicadas using the iNaturalist phone app. Monitors also will be installed throughout Cook County forests to measure their sound. She said the project will “give us a better sense of how numerous they are in different places.”

“The really interesting thing about recording is that when scientists like myself go to listen to them we can tell, is it a chorus, is it just one individual male singing or is it a pulsating chorus where you have a number of males that are now generating enough noise to attract females,” Almassi said.

This year’s cicada phenomenon also presents scientists with opportunities to learn about soil environments, as well as help determine how past land management has impacted the ecosystem where cicadas may not emerge.

Cicadas "tell us about what’s happening in the soil,” Almassi said, likening them to a “window” into the soil environment. “So, if we have a healthy population of cicadas emerging … that tells us that that habitat has been healthy enough for the last 17 years to sustain their population.”

The periodical cicadas, like the annual cicadas, are not invasive and do not negatively impact the ecosystem. But their egg-laying process can cause damage to some trees and plants, prompting the Morton Arboretum in Lisle to protect hundreds of its trees with netting.

“The female cicada has a specialized organ called an ovipositor that will cut into branches like a pocket knife and deposit her eggs inside of the bark, and that can cause branch death or dieback,” said Stephanie Adams, plant health care leader at the Morton Arboretum.

Young or especially small trees are most preferred for cicadas to lay eggs in, as well as wooded shrubs. The twigs impacted by the egg laying are between one-eighth and about half an inch in diameter.

“If you have a preferred host that you just planted in the last few years and it’s still a pretty small tree, you might want to consider protecting it,” Adams said.

Recommendations to protect trees from being damaged throughout the cicada egg-laying process include wrapping the tree with a mesh netting with holes that are a quarter of an inch or less wide. The tree should be wrapped by early May, after leaves develop and before the cicadas arrive, and the netting should be left on for about six weeks.

“With enough branch damage, that basically cuts off sap and water movement within the tree, which prevents photosynthesis, and if there’s not enough photosynthesis for the tree to maintain its leaves, then it will die,” Adams said.

Almassi also urged people to not spray pesticides on cicadas or lawns.

“This is a really cool natural phenomenon, and you don’t want to poison yourself or the many things, from dogs to birds, that eat the cicadas,” she said. “It’s only going to do them and the ecosystem more harm than good.”