This spring and summer, the buzz around town will be the sound of hundreds of thousands of cicadas which are due to emerge in 2021 after a 17-year hibernation underground.
Howard Russell, an entomologist (insect scientist) at Michigan State University says, “The end of May through June, it can get pretty loud – if you are in an area where they are numerous, there can be hundreds of thousands, or millions, of them.”
While there are thousands of varieties of cicadas around the world, the periodical Brood X (there are fifteen in this particular class identified by Roman numerals) remains one of nature’s greatest mysteries and most prevalent in the United States.
The Brood X, with their black-bodies and red-eyes, have been hibernating since 2004 – living approximately one to two feet underground while wingless (referred to as nymphs) where they feed upon the sap excreted from tree roots.
It’s worth noting that their feeding habit does not damage the tree, but aerates the soil and brings important nutrients and nitrogen to the surface, which benefits plants.
According to John Cooley, an entomologist at the University of Connecticut who studies periodical cicadas, “There are perhaps 3,000 to 4,000 species of cicadas around the world, but the 17-year periodical cicadas of the eastern U.S. appear to be unique in combining long juvenile development times with synchronized, mass adult emergences.”
No one knows why after 17 years underground, on a perfect spring day when the soil temperature reaches 64 degrees Fahrenheit, the nymphs collectively burrow to the surface of the soil and molt for the final time.
According to Russell, “At that time they are white – their exoskeleton hasn’t hardened yet. That takes five or six days. Then the adult is ready to look for a mate.”
Why Brood X cicadas do not emerge on the 14th, 15th, or 16th year is not fully understood, but they do use some natural triggers to signal their mass emergence. Scientists believe that Brood X cicadas have a method for counting the number of times a deciduous tree regrows its leaves. They will even postpone their emergence if the weather is rainy or unpleasant.
Russell says, “The cicadas come out after the ‘right’ number. Whatever the specific change is, the cicadas can detect that.”
After the cicadas have mated, the female lays her eggs in soft, new twigs she cuts open using a sharp knife-like organ known as an ovipositor. While not harmful to mature trees, younger trees, shrubs, and ornamentals can be at risk. Weak and broken branches can result in flagging and tip die-back.
So how do you protect young trees from the female cicadas?
There is no preventive treatment to keep cicadas from invading your property. But there are precautionary steps you can take to help strengthen the health of your trees in the event of cicada infestation such as applying bio-stimulants like ArborKelp®. Pruning is also recommended to clean up any broken branches after an infestation has occurred.
The Brood X cicadas will emerge in the spring of 2021 in 15 states: Delaware, Georgia, Illinois, Indiana, Kentucky, Maryland, Michigan, North Carolina, New Jersey, New York, Ohio, Pennsylvania, Tennessee, Virginia, West Virginia, as well as Washington, D.C.
While it’s difficult to pinpoint the date of their exact emergence, the states mentioned above will almost simultaneously begin seeing (and hearing) cicadas around early to mid-May until around late June.
Reference the map above to identify the proximity of Brood X cicadas in your area.
For questions about caring for your trees, contact SavATree today!