The emergence of two broods of periodical cicadas in Illinois this spring will be an event that has not occurred since 1803 and will not happen again until 2245.

What does this rare event mean for Peoria-area farmers?

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Do cicadas destroy crops?

The short answer is, not much.

“Periodical cicadas don’t pose a risk to any of the major crops in Illinois,” said Illinois State Entomologist Christopher Dietrich. “They are restricted to areas with mature natural forest, and they don’t move around much so we’ll see few, if any, in areas dominated by row crops.”

The Peoria area’s corn and soybeans are safe from a dual emergence of the Northern Illinois Brood and the Great Southern Brood. But the billions of insects whose song will begin to fill Illinois evenings later this month can still pose an agricultural threat statewide.

Do cicadas destroy trees?

University of Illinois Extension horticulture educator Ken Johnson wrote female cicadas will cut open tree branches, resulting in a scar that can be several inches long. While the damage will not kill mature, healthy trees; it can kill small trees and shrubs.

“Newly-planted small trees and shrubs may have trunk diameters small enough for female cicadas to lay their eggs in,” Johnson wrote. “If this happens, the trees can be killed. These smaller plants also have fewer branches on them, and egg-laying can cause significant damage to the trees.”

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The female cicada’s affinity for trees means the primary risk is to commercial tree fruit growers. Richard Tanner, the father of Tanner’s Orchard owner Craig Tanner, still helps out at the Speer, Ill., farm, and said 3,000 new trees were planted there last spring. To make up losses from last year, Tanner’s also plans to replant trees this spring.

“Due to the warm and dry conditions of spring 2023, we lost about 15% of the trees and will be replanting them,” Tanner said.

How to protect young trees from cicadas

The Illinois Department of Agriculture said the best way to protect small trees from cicada damage is to surround the trunks with screening, which will curtail egg-laying. IDA said commercially available pesticides don’t work on cicadas and could negatively affect pets and wildlife that feed on them.

University of Illinois Extension assistant professor Kacie Athey wrote late in April that the best protection for vulnerable trees is protective fine-meshed netting. However, for growers with large numbers of fruit trees, there are insecticides available only to commercial fruit producers.

Athey provided a spraying guide for commercial growers, including a list of available insecticides and efficacy ratings for each. Of the eight products listed, five had ratings of “Unknown.” Asana XL and Danitol 2.4EC received scores of “Excellent,” and Athey gave Sevin XLR Plus a rating of “Good.”