It has almost been a year since the last emergence of cicadas in Tennessee. Now, brood XIV is set to reemerge in the Eastern United States in the coming months when the underground soil reaches optimal temperatures.
According to USA Today, Brood XIV is a massive group of 17-year periodical cicadas last seen in 2008. After nearly two decades below ground, billions will rise again.
USA Today also states that Tennessee is expected to have one of the largest concentrations of these cicadas, alongside parts of Kentucky and Georgia.
“They’ll be there for four to six weeks maximum — so, starting when the temperature is around 64 degrees is when they start coming, so somewhere closer to May,” Midhula Gireesh, assistant professor in the Department of Entomology and Plant Pathology at the UT Institute of Agriculture, said. “So if you want to time anything according to that, that’s probably the timeframe they’d be here.”
While cicadas are not particularly harmful — they do not bite, sting or carry disease — the primary concern is for ornamental plants and young trees. These plants can suffer damage when cicadas lay eggs on small branches, according to the University of Tennessee Institute of Agriculture.
UTIA explained that valuable shrubs, small trees and ornamental plants can be shielded with cheesecloth or tobacco canvas while cicadas are active. According to UTIA’s Periodical Cicadas report, insecticide spray is not recommended to prevent cicadas from laying their eggs and damaging plants.
Ivey Woolf, a senior studying plant sciences, elaborated on the damage this brood of cicadas could have on plant life in Tennessee.
“Cicadas are herbivores, meaning they feed on plant material — these insects don’t have a specific focus like other insects, such as leafminers, they instead attack all parts of the plant,” Woolf said. “The immature stages of the insect will feed around the roots and stem of the plant, while the adults will consume the leaves.”
The cicadas’ mass appearance is a fascinating natural event — after emerging, the cicadas will mate, lay eggs and die within four to six weeks. Gireesh explained the life cycle of these cicadas.
“They have a life cycle that’s either 17 years or 13 years — so this is the time that they will be spending underground in immature form,” Gireesh said. “It starts by making small holes, and then they come out and they need an upright structure. Once they climb, they change from immature forms to adults — they shed their exoskeleton.”
For students at UT, Brood XIV could become an audible and visual part of campus life, affecting outdoor sports and spring events later this semester.
According to Gireesh, cicadas can reach 92 to 100 decibels with the males’ mating calls — this can be as loud as a jet taking off at 305 meters.
Woolf explained that Brood XIV could affect not only plant life and disturb audio levels but also local businesses.
“Economically speaking, the agricultural and green industry will most likely take a hit as well,” Woolf said. “With the majority of the green industry having operations outdoors, their plant stock may take a major hit.”
Gireesh explained that despite the potential for impairment, cicadas can bring many ecological benefits.
“Them coming in this many numbers is food to a lot of predators,” Gireesh said. “They also act as natural aerators from making those holes and then once they die off, all their dead bodies are like a natural fertilizer.”
As Tennessee prepares for the arrival of Brood XIV, city planners, arborists and farmers should be advised to take preventive steps to ensure the health of Knoxville’s green spaces.
“The problem mainly lies with the management of this event, especially since we know that it is coming,” Woolf said. “Questions regarding the use of pesticides, biological control and preservation of stock must be addressed in order to prepare fully for the emergence of Brood XIV cicadas.”
