Chicago, welcome to cicada season.
For the past 17 years, billions of periodical cicadas from Brood XIII have lived underground in the Chicago area, drawing on fluid from plant roots. And although they typically emerge in mid-May and June, some have started showing up early, according to the Morton Arboretum in Lisle, Illinois.
“The periodical cicadas have been emerging for the last week and a half,” Stephanie Adams, a plant pathologist at the Morton Arboretum in Lisle, said Tuesday of brood XIII, which will soon spread throughout the Chicago area. “We found them both here in our landscape and also in our eastern woods.”
Once they dig into the ground, they head to trees and wooded areas for about four to six weeks, where they mate, lay eggs and sing.
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According to Adams, the emergence of the first cicadas occurs about two weeks earlier than the historical average. This will continue to be sporadic, as soil temperature, mulch, and turf all impact cicadas differently. For example, the ground is warmer near sidewalks, so cicadas in those locations should emerge more quickly.
“Everything in biology always has a gradient,” Adams continued. “So you always have some early emergers and then others that will emerge a little late.”
Once they’re out in large numbers, there’s no escaping them – and that goes for your trees, too.
How to protect your trees from cicadas
Generally, cicadas are harmless, Adams said. They do not bite, do not have stings and are beneficial to the environment. But they can cause damage to small, vulnerable trees and shrubs, Adams said.
According to Adams, young plants, two to three years old, are most vulnerable, as are smaller plants, with branches less than two inches in diameter, which are at risk. They may not be able to recover from the damage caused by female cicadas laying eggs, Adams said.
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“This damage is caused when the female begins to lay her eggs,” Adams explained. “It has a specialized organ that cuts plants, trees and shrubs and lays its eggs inside the thin bark.”
According to the Arboretum, one way to protect your trees and shrubs would be to use tulle as a protective wrap and barrier. The tulle material is particularly recommended because it is breathable and allows sunlight to penetrate the plant.
“You’re looking for netting that’s no more than a quarter of an inch in diameter, the more the cicadas can climb and defeats the purpose of protecting them,” said Spencer Campbell, director of Plant Clinic.
Homeowners are encouraged to begin protecting their young plants as soon as possible and keep them wrapped until mid-June when emergence ends.
What types of trees are most vulnerable to cicadas?
According to the Arboretum, cicadas are “not peculiar,” meaning they use a variety of trees and shrubs as hosts.
“However, only very young trees or older trees in poor health or stress are at risk,” the Arboretum said.
The insects are known to lay eggs in oaks, maples, hickory, apple, birch, dogwood, basswood, willow, elm, ginkgo and pear trees, according to the Arboretum.
“Cicadas can also lay eggs in certain shrubs, such as rose bushes, lilacs and forsythia,” the Arboretum said. “They tend to avoid conifers like pine, spruce and fir.”
Arboretum records show that during the emergence 17 years ago, some of the plants most affected by the emergence were maples, cherries, ashes, hawthorns, willows, mountain ash, oaks, pear trees, rose bushes, privet, poplars, saskatoon berries and beeches.
Do pesticides work on cicadas?
A message from the city of Lake Forest advised residents to “avoid planting young trees less than 2 inches in diameter” and to cover young trees with netting. The city also advised residents not to use insecticides.
According to the Environmental Protection Agency, pesticides are “generally ineffective in repelling cicadas.”
“So many cicadas emerge at the same time that others will inevitably move in,” the agency said. “Spraying also doesn’t make sense because cicadas are generally harmless. Applying pesticides to control cicadas can harm other organisms, including animals that eat cicadas.”
Can you limit the number of cicadas in your garden?
Frank Meek, technical services manager for pest control company Orkin, said NBC Chicago exterminators generally don’t treat cicadas because they don’t pose a threat to humans, animals or property.
Additionally, chemical treatments are generally ineffective against cicadas due to their short lifespan, Meek added.
“Cicadas are an important part of the food chain and serve as meals for birds, moles, raccoons and some frogs,” Meek said. “It is important that humans leave cicadas alone so that other animals can benefit from this food source.”
Cicadas are not considered pests, Meek said. But they are known to enter homes without being invited.
“Cicadas fly strong but clumsily and can accidentally fly into homes if windows and doors are left open,” Meek said. “However, because cicadas cannot breed indoors, an indoor infestation cannot occur.”
According to Meek, cicadas found in yards and gardens can be “gently” removed by hand. And while Orkin doesn’t advise treating cicadas around homes, there is an extra layer of defense homeowners can adopt to keep cicadas away, the company says.
“Homeowners can also prevent cicadas from taking up residence in their trees and bushes by wrapping the base in foil or duct tape,” Meek said. “This prevents cicadas from climbing the tree or bush to feed or lay eggs.”
Still, experts say, it may not be worth it. After all, there will be billions of them.
“You absolutely should not try to eliminate them from an area that has billions of them,” said Allan Lawrance, associate curator of entomology at the Peggy Notebaert Nature Museum in Chicago.
Although this year’s emergence is only just beginning, it is expected to peak in the coming weeks.
“There’s no way to stop them,” said Allen Lawrance, associate curator of entomology at the Peggy Notebaert Nature Museum in Chicago. “They’re here. It’s temporary, and there’s really no way to escape them.”
NBC Chicago
