As I write this, I’ve just started receiving reports that the 13-year cicada has begun to emerge. By the time you read this, most parts of the Tri-State should be seeing these noisy critters.
The periodical cicada, also sometimes called a locust, is a fascinating insect. Depending on the type, or brood, these insects spend either 13 or 17 years underground, feeding on the roots of trees. At maturity, the cicada nymph will emerge from the ground. They’ll crawl up tree trunks, fence posts, or other objects, shed their exoskeleton, and become winged adults.
The adult periodical cicada is about 1 and 5/ 8 inch long. They have black bodies; their legs, wing margins, and eyes are red. The adults live for about a month, usually emerging in late May and through June. We last saw this brood (Brood XXIII) in 1989.
The "dog-day" or annual cicadas appear during the long summer days of July and August. These cicadas have two to five-year life cycles but their broods overlap and some appear every summer. Dog-day cicadas are larger than periodical cicadas and have green to brown bodies with black markings and a whitish bloom. Their wings have green veins. Annual cicadas do not ordinarily cause much damage.
Male cicadas make a high-pitched, shrill mating call. This can get quite deafening, especially when numerous males all congregate in the same tree. They make this noise by vibrating a membrane on their abdomen. The females have no sound-producing organs, and are silent.
Cicadas can do quite a bit of damage to trees, but not in an obvious way. The adults don’t feed on the tree, but the nymphs suck the sap out of the tree roots. Large numbers of cicadas can do enough feeding over the years to seriously weaken a tree.
The females can lay up to 400 to 600 eggs. She uses a knife-like organ, called an ovipositor, to slit or puncture the twigs of woody plants to lay her eggs. Infested branches appear as if the eggs have been stitched in by a sewing machine. This damage causes twigs to split, wither, and die, causing a symptom called "flagging." Sometimes these twigs break off, littering the yard with numerous broken limbs. About 6 weeks after the eggs are laid, the nymphs hatch out and drop to the ground, where they dig into the soil in search of tree roots to feed on.
Female cicadas prefer to lay their eggs on maple, oak, hickory, and flowering trees; they also can attack Rose of Sharon, rose, raspberry, grape, hollies, rhododendron, and other shrubs.
Adult cicadas do not bite, nor do they sting. They are not poisonous or otherwise dangerous. The worst thing about them is their noise; although in some areas, heavy infestations can make the sidewalks and roads slick with dead insect carcasses.
Periodical cicada emergence is very spotty in the Midwest. They are abundant only in areas where trees harbored the eggs of the previous generation. They can be very numerous in some areas and absent in nearby woodlots. Areas that historically had heavy infestations may not have them this year, especially if the woodlots have been paved over for development (OK, finally a good use for strip malls: cicada control!).
Cicada control is very difficult, partly due to the huge numbers that suddenly appear. Birds, squirrels, and cicada-killer wasps will feed on them, but there are far too many insects for these animals to adequately control.
Chemical control is not warranted in most home situations: the adults are not feeding, so they are unlikely to be killed by residual products. Since they are strong (but clumsy) fliers, even if you knock a bunch out of your tree with a contact insecticide, more will be there the next day. Also, a study in 1990 by the University of Illinois compared trees that had been sprayed with those that hadn’t. Both had about the same amount of egg-laying damage, showing that there’s no benefit to spraying.
Despite this, if you feel you MUST spray your trees, you can use carbaryl (Sevin) every 5 to 7 days. A better choice might be any insecticide with pyrethrum or permethrin as the active ingredient, as these products are reported to have a slight repellant action. Nursery and fruit tree growers have other commercial products they can use.
Your best option is to cover small ornamental trees and susceptible shrubs with cheesecloth or mosquito netting. Be sure to seal it carefully at the base of the trunk. This prevents the females from climbing or flying into the tree to lay their eggs.
For more information on periodical cicadas, or to report a local emergence (we are trying to track them for future outbreaks), contact the Purdue Extension Service at (812) 435-5287, or e-mail me at Larry.Caplan@ces.purdue.edu.
Periodical and "Dog-Day" Cicadas -- from Ohio State University
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