URBANA, Ill. - The long-awaited 2024 cicada emergence is finally underway in parts of Illinois and the Midwest. Two broods of periodical cicadas (known as Brood XII and Brood XIX) had been reported in both central and southern Illinois as of Friday, May 17, according to University of Illinois Extension horticulture educator Ken Johnson.

“I’ve also seen people posting pictures of them emerging in the Chicago area,” Johnson told Farm World. “They have been singing in southern Illinois and have started singing in Jacksonville.”

The dual-brood emergence, which Johnson said is a once-in-a-multi-generation event, will occur in 17 states. Such a co-emergence has not occurred in 221 years and won’t happen again until 2245, according to entomologists. A few places in central Illinois, such as Springfield, may host both emerging broods. However, the broods are not expected to overlap to any great extent.

Cicada emergence no threat to crops or livestock

Thankfully, cicadas do not pose a general threat to crops, garden plants or animals — although your newly planted tree or shrub may be a different story. 

“As female periodical cicadas lay their eggs, they will cut open branches with their ovipositor. This will result in a scar that can be several inches long. These damaged areas may sometimes break, which will cause everything past this damaged area to die. This is often referred to as flagging. Fortunately, this will not kill healthy, mature trees. The same can’t be said for small trees and shrubs, though,” Johnson explained in a recent blog. 

“Newly planted small trees and shrubs may have trunk diameters small enough for female cicadas to lay their eggs in; 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.”

Now that cicadas are emerging, Johnson recommends the following measures to prevent damage to fledgling trees and shrubbery:

Place netting around small trees and shrubs (up to 10 feet tall), making sure it is secured around the base of the plant to prevent cicadas from crawling up the plant from the ground. The opening should be no larger than ¼ inch. It may be helpful to build a frame around the plants, cicadas may still be able to lay eggs on branches that are touching the netting. 

Twigs and branches that have had eggs laid in them can be pruned off to prevent the nymphs from reaching the ground and feeding. However, feeding by cicada nymphs does not seem to be harmful to the trees they feed on.

Insecticides are not recommended to manage periodical cicadas in home landscapes. Large, healthy trees are able to survive egg-laying with no long-term impacts (this has been happening for thousands of years). Insecticides are not as effective in protecting smaller trees and shrubs from cicadas as netting. Additionally, applying pesticides to control cicadas may harm other organisms, including animals that eat cicadas.

Johnson noted that periodical cicadas will lay their eggs in just about any woody plant that is up to 0.5 inches in diameter. “That being said, they do have some plants that they prefer to lay their eggs in, like oak, maple, hickory, apple, birch, dogwood, linden, willow, elm, ginkgo, and pears. They tend to avoid plants that produce a lot of sap or gum, like conifers, cherries, peaches, and plums, because this could prevent eggs from hatching and nymphs from reaching the ground,” he said. 

What to expect next

A few weeks after emergence, female cicadas will spend most of their time above ground reproducing. Each female will lay around 500-600 eggs.

“After about a month, the adult cicadas will begin to die. Large piles of cicadas can accumulate under trees and can smell rather unpleasant (similar to roadkill). However, their decaying bodies will serve as fertilizer for plants,” according to Johnson. “Six to ten weeks after they are laid, the eggs will begin to hatch. The tiny cicada nymphs will drop to the ground and begin feeding, often on grass roots. Over time, they will dig down into the soil, 8-12 inches deep, and feed on tree roots for the next 13 or 17 years.”

Though the emergence of the broods is expected to be somewhat noisy and potentially messy, Johnson is among the people who are excited and fascinated to witness the rare event. In his blog, Johnson called attention to the benefits of the cicada explosion:

As they dig their tunnels to the surface, they help aerate the soil and improve water infiltration into the ground.

Their egg-laying can provide some natural pruning to trees. This pruning can lead to a flush of growth and increased flowering and fruit production the following year.

When cicadas die and begin to decompose, they release nutrients into the soil, particularly nitrogen. This natural fertilizer can lead to increased growth of plants and an increase in soil microbes. Studies have found that sycamore trees grew 10 percent more than trees that were not fertilized by dead cicadas, and American bellflowers grew 61 percent larger and produced seeds that were 9% larger than unfertilized plants.

Periodical cicadas will serve as a food source for a wide range of animals. A variety of birds, including grackles, robins, blue jays, red-winged blackbirds, sparrows, and woodpeckers, will feed on them. In emergence years, birds will often have more offspring, and more of them will survive.

In addition, mammals like squirrels, raccoons, and skunks, as well as insects, cats and dogs will readily feed on periodical cicadas. 

“While this mass emergence may seem overwhelming or disgusting to some, it is important to remember that periodical cicadas are not poisonous or venomous, nor do they bite or sting, and don’t pose a threat to humans or animals,” Johnson said in his May 17 Extension blog: “Periodical cicadas are here…now what?” (www.Illinois.extension.edu)