Should Illinois homeowners and gardeners be worried about the cicada emergence?

Despite their loud, aggressive-sounding buzzing and red-eyed, rather frightful appearance, the periodical cicadas due to emerge en masse this spring in Illinois do not pose a threat to humans, pets or mature, healthy trees. But their egg laying might put newly planted trees or shrubs at risk. Should homeowners or gardeners be concerned?

For the most part, no, said Kacie Athey, a specialty crops entomologist with the University of Illinois Extension. "Most plants in anyone's yard are probably not in danger from periodical cicadas," she said.

What is the egg-laying risk?

When periodical cicadas emerge in all their millions after spending years underground, the males sing their loud courtship song. After mating, the females lay their eggs.

The females generally create slits in twigs to hold the eggs, but will also deposit them elsewhere on a tree, according to the extension. A slit in a twig may cause the latter to dry and break off, but the damage is not harmful enough on an established tree to justify control measures. But small transplanted trees, especially fruit trees, might have small-enough trunks that egg slits made there may result in the tree snapping off. "The only way to protect small trees from serious damage in a heavy emergence area is to protect the trunk with screening or other material," the extension adds.

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How can homeowners protect young trees?

Athey recommended that, for any kind of young tree, homeowners put some mesh down to ensure that the damage from cicadas isn't too deep. But she cautioned, "I would never recommend that homeowners use insecticides against them." Additionally, using broad-spectrum pesticides to control cicadas may be harmful to other insects, she said.

Will cicadas eat my trees?

Adult periodical cicadas do feed on plants, contrary to popular belief. But they are particular about their food, reports USA TODAY, which adds they only drink sap from plants with woody stems and branches, the same places they lay their eggs. But they spend most of their time above ground reproducing, says the extension.

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Will cicadas eat my garden plants?

While they may swarm over your tomato vines and marigolds, they won’t harm your garden vegetables or flowers, adds USA TODAY. Cicadas also won't harm your lawn. You may find emergence holes and small mud “chimneys” — one East Peoria resident's property was described as "a swiss cheese" in a 1956 Peoria Journal Star article — but they won’t permanently damage your yard, and may provide helpful aeration. Indeed, the rotting adult bugs act as a nitrogen-rich fertilizer.

"Anything growing in your garden should be safe," confirms Athey.