DUANE SHERRILL
Contributor
Here we go again. Just when you thought it was safe to go outside without the shrill sounds of cicadas ringing in your ears – they’re back.
Brood XIV (14) is emerging from the ground, rising up after 17 years of dormancy right beneath our feet. The coming invasion comes just a year after Middle Tennessee was treated to the drone of Brood XIX which was a 13-year brood.
“This year we will see the 17-year cicada brood XIV (14) emerge in Tennessee,” Dr. Karla Addesso, Entomologist and Director of the Tennessee State University Nursery Research Station in McMinnville revealed. “Emergence will start in May when the ground temperatures warm up.”
The brood is also expected to extend to mid-state counties such as Lincoln, Warren, Grundy, Marion and Cannon.
According to information provided by Dr. Addesso, cicadas usually emerge in early May. Their numbers can differ greatly in density across the emergence area. After five days or longer and depending on temperature, adult cicada activities begin, both in flight and song, as they gain strength in their muscles. Adult males usually produce characteristic sounds in chorus trees during courtship to attract females. This high-pitched, shrill call is produced by two drum-like membranes on the side of the abdomen.
Adult periodical cicadas are medium-size insects. The body is black, while the legs, eyes and wing veins are reddish-orange. Mature nymphs are commonly found within the top few inches of soil. When soil temperatures reach 64 degrees nymphs will begin digging to the surface. Following mating, the female cicada uses her knife-like ovipositor to deposit eggs into slits made on twigs. The female can lay 24 to 28 eggs in each slit and will repeat this procedure, cutting numerous slits along the same branch and depositing more eggs. Each female can lay approximately 400 to 600 eggs during her lifetime, which can be four to five weeks.
Egg laying is the major cause of cicada damage in nurseries and newly planted orchards. Egg laying punctures causes the twig tips to wilt and leaves to turn brown; a condition referred to as “flagging”. Also, egg-laying wounds can serve as entry routes for other insects and diseases. After about a month, eggs hatch into wingless white nymphs with an ant-like appearance. These nymphs fall from tree branches and dig into the moist soil using modified front legs until a suitable root is found. Cicadas have piercing-sucking mouthparts, and nymphs feed by sucking xylem sap from the roots. The nymphs continue to feed and develop for 13 or 17 years, depending on the species. In their final year, the mature nymphs will emerge from the ground shortly after sunset and crawl onto a vertical surface, which is often the bark of young trees or neighboring vegetation. At this stage, they molt for the last time and metamorphose into fully-winged adults on young trees during nighttime hours between 6 p.m. and 9 p.m. During this process, the old empty exoskeleton is left behind. Over a few hours, the wings expand fully, and the body obtains its natural pigmentation. Once the adult is fully hardened, it will fly into a nearby tree canopy and the life cycle repeats.
Egg-laying damage by female cicadas have been observed on over 200 woody tree species. Woody trees with the most noticeable symptoms include American hop hornbeam, American hornbeam apple, ash, cherry, cypress, dogwood, elm, grapevines, hickory, maple, oak, peach, pear, redbud, serviceberry, and willow.
During insurance appraisal of egg-laying damage in 2011 by Brood XIX (13-yr cycle) at seven Middle Tennessee nurseries, those trees determined to be “Damaged Beyond Repair” included: seven species of oak, four species of maple and cherry, three species of redbud and peach/plum, and two species of elm, dogwood, and willow; single species included golden raintree, holly, honey locust, London plane tree, serviceberry, sourwood, sugarberry, and tulip poplar.
Small trees can be protected by enclosing them in cheesecloth, tobacco canvas, mesh screenings (<1/2-inch or 3/8-inch openings, and polypropylene fabric. Ahern reported netting gave the best protection and cost less than chemical control. Covering protection should be applied just before emergence until adults are gone 6–8 weeks later. Protect ponds in ornamental plant facilities with screen or plastic mesh to avoid any buildup and decay of periodical cicadas (oxygen depletion of water has been observed when decaying cicadas are present); and regularly clean irrigation pond skimmers or filters during periodical cicada emergence to avoid any blockage.
