DUANE SHERRILLContributor

Brood XIX is about to make its first appearance since 2011 bringing ear-splitting noise and potential for plant damage as billions or even trillions of the cicadas will make themselves known pretty soon for just over a month before disappearing for another 13 years.

Middle Tennessee appears to be in the cross-hairs of this year’s emergence. Brood XIX is only one of the broods that impact this area. Brood XIV, for instance, will return next year after last being seen in 2008, making them a 17-year cicada.

According to information provided by Dr. Karla Addesso, Entomologist and Director of the Tennessee State University Nursery Research Station in McMinnville, 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.

As for their numbers, Dr. Addesso said that Cicada scientists believe that emerging every 13 or 17 years in huge numbers is their defense. It is referred to as the ‘predator satiation hypothesis.’ Since the insects have no physical defenses, they overwhelm predators by emerging in such high numbers that the predators can’t eat them all. That allows the survivors to mate and lay eggs safely after the predators in the area are full. They can be as dense as one million per acre.

Dr. Addesso noted that one thing that is sometimes overlooked about the outbreak is that they often can make meals for not just animals but also people.

“You can think of cicadas as ‘land shrimp’. Eating them is safe as long as you are not allergic to shellfish,” she said. “There are a number of free recipe books online. The newly emerging cicadas are the best to eat because their shells have not yet hardened. To collect these, wait until 9 pm, grab a headlamp, find a large tree and look for cicadas hanging upside down, emerging from their nymph skins. They will be a creamy white color.”