Cicadas are an annual “sound of summer” across many parts of the Midwest and East Coast but the chorus will be even louder than usual in some areas this year. Folks in Virginia, North Carolina, and West Virginia will see far more of the bugs this summer as Brood IX emerges from the ground after 17 long years.
Science has learned that cicadas begin to emerge when soil temperatures eight inches deep reach 64 degrees Fahrenheit. I should note, warm rain has been known to often trigger an emergence. In addition, these cicadas will emerge after the trees have grown leaves and around the same time Iris flowers bloom.
The life cycle of a cicada is unlike any other creature on the planet. Surviving females will lay as many as 600 eggs each which are deposited into slits they’ve cut into tree branches. About 6 to 8 weeks later the eggs hatch and the nymphs fall to the ground. Those that don’t get eaten burrow into the ground, down past the frost line until they find roots to feed on. There they spend up to 17 years underground where they will molt four times. Somehow, they know precisely when they are supposed to emerge, and millions – maybe billions – begin swarming up out of the ground. They then molt one more time, leaving behind a hard brown exoskeleton on tree branches usually. Essentially, they spend their very brief life above ground looking for a mate. Males start their deafening singing, females respond, mating begins, and after about two weeks, it’s all over for the adults.
Believe it or not, scientists actually warn that cicada calls are loud enough to cause “physical and psychological strain ” in humans. Entymologists estimate that Tibicen walkeri, a North American cicada, can emit sounds hitting 108.9 decibels. According to a loudness scale, that’s noisier than a jet during takeoff, a power lawnmower, and a jackhammer. The U.S. Occupational Safety and Health Administration rules say that 8 hours of exposure to noises reaching 90 decibels, or two hours of exposure to 100 decibels, are the maximum permissible levels for noise safety. In addition, many experts estimate the number of cicadas at 1.5 million per acre, so you can imagine how loud they are. The only way to really get any peace and quiet is to go inside and shut the windows. It will all be over in about five to six weeks!
Some species of cicadas maintain what’s known as “brood cycles”, only emerging every 13 or 17 years. There are 15 known cicada broods that scientists track. This summer’s appearance will be made by Brood IX, which literally hasn’t seen the light of day for 17 years.
Cicadas from other broods will also emerge this year in small numbers. When cicadas emerge early or late, they’re called stragglers. Members of Brood XIX (19) are emerging in parts of North Carolina and Georgia, where Brood XIX is know to exist. You might see them in Alabama, Arkansas, Georgia, Illinois, Indiana, Kansas, Kentucky, Lousiana, Missouri, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee, and Virginia. The rest of Brood XIX will emerge in 2024.
They are sometimes called the 17-year locust but cicadas are very different creatures. Locusts are a type of grasshopper that swarms in from other areas, devouring every inch of vegetation in their path. Cicadas can cause crop damage but not anywhere close to locust-level devastation.
Cicadas are a particular threat to fruit trees as the adult females cut slits in the soft new growth of twigs on woody plants to lay their eggs. This is called “flagging” and is most damaging to small young trees. Large, established trees can often have large amounts of flagging but rarely suffer severe damage. Cicadas can also spread pathogens with outbreaks of some diseases, like fire blight for instance, following the egg-laying of periodical cicadas
Another form of damage inflicted by cicadas might be caused by their hatchlings feeding on tree roots. The full extent of the damage this can do to tree growth doesn’t seem to be fully understood, though. A study of one group of trees during an emergence in the Hudson Valley in N.Y found that trees that had the ground protected beneath them when the nymphs dropped down grew more than the others but scientists haven’t determined if the effect is important or not.
Entomologists actually recommend growers not plant fruit-bearing trees for a couple of years before an emergence as it’s extremely difficult if not impossible to entirely avoid cicada damage during a brood emergence. That’s something to keep in mind because 2021 will see one of the biggest cicada invasions we’ve witnessed in a long time.
Billions of cicadas will appear in Delaware, Georgia, Illinois, Indiana, Kentucky, Maryland, Michigan, North Carolina, New Jersey, New York, Ohio, Pennsylvania, Tennessee, Virginia, West Virginia, and Washington D.C. when Brood X emerges next spring. Interestingly, after that, the next brood won’t emerge until 2024, which is expected to be a doozy as that will be Brood XIX, arguably the largest by geographic extent of all the broods, with records along the east coast from Maryland to Georgia and in the Midwest from Iowa to Oklahoma. Mark your calender…
Gene Kritski, the dean of behavioral and natural sciences at Mount St. Joseph University in Cincinnati, developed the Cicada Safari app to help track the invading swarm. When a cicada is spotted, users can use the app to take a photo and submit the pictures for inclusion on the map, which will help everyone know when the emergence is near you. Click HERE to view the most up to date maps! (Sources: CicadaMania, Magicicada, Charlotte Observer)