By Anna Hughes | Photos courtesy of the The Morton Arboretum

A rare ecological event is happening this spring and summer, but it comes with lots of crawly legs and beady eyes.

For the first time in 221 years, two broods of cicadas (Brood XIX, which arrives every 13 years, and Brood XIII, which comes every 17 years) will be making their way above ground at the same time.

This is the first time this has happened since 1803, when Thomas Jefferson was president. In 2024, the United States will see a trillion cicadas, but what does that mean for us here in Illinois?

Illinois will experience both broods at the same time. The west suburbs of Chicago will experience Brood XIII, which inhabits the northern third of the state and parts of lower Wisconsin.

The southern parts of the state will see Brood XIX. While entomologists recommend enjoying this rare occurrence, they say to expect a lot of noise and a lot of bugs.

Warning: Potential Plant Damage

Cicadas, however, are more than just pesky. They can be very damaging to trees and plants during the spring and summer months. We spoke with Morton Arboretum Plant Health Care Leader Stephanie Adams, who offered some advice on how to protect against insect invasion.

1. Avoid planting new trees (if possible) until late summer or fall. This is best to prevent the young plants from experiencing too much damage in their early growth stages.

2. Grab some tulle or netting and wrap up your trees! Female cicadas inject their ovipositor, a sharp external organ, into a branch just underneath the bark to lay eggs so they’re protected. This cuts slits into the underside of small branches. Adams explained it’s not normally where people think about looking for insect damage because it’s actually on the underside of branches instead of the top. For people with manicured gardens, she suggests buying protective fabric sooner rather than later!

3. Pesticides are not necessarily the answer here. Studies have not proven that pesticides are helpful for large-scale problems like cicadas. As for contact insecticides, they should be avoided because they would likely be damaging more non-target organisms than cicadas.

4. Don’t cut off branches that seem to be damaged. Adams said that as long as the leaves are green on the trees, they are still photosynthesizing. It’s better to wait until the branch is fully dead to cut it off to avoid doing excess damage to the tree.

The good news is that cicadas are native insects, so native trees should not suffer too much from their emergence. Typical damage is no more than native pruning. It’s vital that other trees or plants you may have added to your lawns and gardens receive adequate protection, especially young ones.

For those wondering how to properly cover their plants, the Arboretum is a great place to see examples of proper netting.

Which trees do cicadas prefer?

The arboretum’s website says that preferred plants for egg-laying include apple, hickory, maple, and oaks. Members of the birch, dogwood, walnut, willow, linden, and elm plant families may also be used.

They may also lay eggs in introduced exotic ornamentals such as rose, cotoneaster, forsythia, ginkgo, pear, and lilac.

Cicadas tend to avoid plants whose sap or gum may prevent egg hatch or keep nymphs from escaping, such as conifers, sumac, cherries, peaches, plums, and persimmon (Brown and Zuefle, 2009).