YOUR GARDEN — Plant Information

Pests, Problems, and Diseases

Periodical Cicada (17-year)

(Magicicada sp.)

Click here to hear the cicada!

Annual cicada and exoskeleton

17-year Magicicada sp.

Magicicada exoskeleton

Cicadas are often mistakenly referred to as locusts. Locusts are members of the grasshopper family. Grasshoppers chew for nutrition, while cicadas have sucking mouthparts that do not chew. Periodical cicadas will not bite. They have been known to land on people, however, they cause no harm. Even though adult cicadas suck on plants for nutrition, they feed very little as adults.

The 17-year life cycle of cicadas is a mystery to entomologists. Periodical, or 17-year cicadas (Magicicada genus), require this time in the nymph stage, developing underground, and mature very slowly.
Most fascinating is the fact that they are all synchronized to emerge together, every seventeen years. Their 17-year life span makes them the longest-lived insect known. There are two races of periodical cicadas (Cicadidae family) that are distinguished by the time required to develop into adulthood: the 17-year cicadas, which appear in the north, and the 13-year cicadas, which appear in the south.

Cicada exoskeletons on tree trunk

PHOTO: cicada scarring on tree limbs

Tree damage from female egg-laying

17-year periodical cicadas are scheduled to emerge in the spring of 2007. Nymphs emerge from the ground when soil temperatures warm to approximately 64 F, usually sometime in May. They usually emerge from the ground after sunset, leaving behind very visible exit holes, and quickly crawl to any nearby vertical structure, preferably a tree or shrub. They shed their skins as they molt into adults, leaving behind their empty shells. Shortly after molting, their wings unfurl and their yellow-white skin darkens as their exoskeleton completely hardens.

Adults begin mating after they have completely matured, usually within a few days, and remain alive for approximately 3-4 weeks. Shortly after mating, females climb to living trunks, branches, and twigs, where they split the bark and deposit approximately 24-48 eggs. Adult females mate many times and are capable of laying up to 600 eggs during their lifetimes. Approximately six to ten weeks after egg laying, called oviposition, eggs hatch into ant-like insects, then drop to the ground where they burrow anywhere from a few inches to over a foot in the soil. They remain underground as nymphs, feeding on tree and shrub roots, for seventeen years.

Male cicadas will call females to mate, as well as other males into chorus, by vibrating their tymbals, which are two, rigid, drum-like membranes, located on the undersides of their abdomens. Different species produce different songs. Oftentimes, large groups of singing male cicadas can be deafening. Females do not have tymbals, therefore are incapable of producing the same sounds.

Periodical cicadas are not the same species as the annual cicadas. Even though annual cicada nymph development cycles are also very long and variable, they are not synchronized like the periodical cicadas. Annual cicadas mature at different times, explaining why we see them each year. Annual cicadas are green with black and are also larger than periodical cicadas, approximately 1.5-2.5” in length, and appear July to September. Periodical cicadas are black with orange wing veins, red eyes, approximately .75-1.5” in length, and appear from May to July.

Susceptible Plants
Damage to woody plants occurs primarily when females split the bark on small diameter limbs and branches for egg-laying. Healthy and larger diameter trees and shrubs can easily heal the half inch to one inch slits; smaller ones often wilt and die.

Developing nymphs feed on plant roots underground, which can damage trees and shrubs by producing reduced plant growth.

Newly planted and small diameter trees and shrubs can be protected with a fine netting, cheesecloth, or row cover fabric tied securely at the base, to keep nymphs from crawling up the trunks upon emergence, as well as, preventing females from slitting bark for egg-laying.

Remove small, damaged branches to keep eggs from hatching and future populations low. Also, delay planting new trees and shrubs until adult periodical cicadas are gone, usually by mid-July.

Damage
(See above.)

Treatment & Solutions
The use of chemical sprays to kill adult periodical cicadas is not recommended. Using insecticides will also kill beneficial insects that feed on harmful insects and can injure natural predators, such as birds, raccoons, skunks and moles.

Cicadas are edible; they're even considered a delicacy in many countries, as well as in different parts of the United States. Some claim that cicadas are high in protein, but recent research conducted at the University of Cincinnati’s College of Engineering has determined that cicadas may contain high levels of mercury. Diners therefore are cautioned to limit their ingestion of these "delicacies" to just a few.

For additional information, call the Plant Information Hotline at (847) 835-0972.