Periodical cicadas

What is periodical cicadas?

Periodical cicadas are native insects in the genus Magicicada (NC State notes many cicada species are native to North America). Three 17-year species live in Pennsylvania. Nymphs spend 13 or 17 years underground feeding on root sap, then come out within a few weeks when the soil warms to about 64°F, usually late May or early June in Pennsylvania.

Adults live three to four weeks. Males sing loudly. Females cut slits in twigs 3/16 to 7/16 inch thick and lay eggs inside, 400 to 600 eggs per female. The slit twigs often turn brown and break, which is called flagging. Penn State says large, healthy trees usually recover, but small or stressed trees, including newly transplanted and balled-and-burlapped trees, can be badly damaged or killed.

That matters for anyone planting trees. Purdue and Penn State both advise against planting or transplanting trees in the fall or spring before an emergence in your area. If you must, cover small trees with netting until the cicadas are gone.

People and pets: Penn State says cicadas do not bite or sting and are not a threat to people or pets; they are mostly a noise nuisance.

Signs and damage

• Huge numbers of black, red-eyed cicadas and loud chorusing in late May and June
• Empty nymph shells on trunks, posts and other objects
• Rows of slits in twigs that look 'stitched'
• Twigs that turn brown, die back and sometimes break off (flagging)

Periodical cicadas identification: what to look for

• Adult: About 1 1/2 to 2 inches long, black with red-orange eyes, reddish legs and orange wing veins. Magicicada septendecim is largest with wide orange belly bands; M. septendecula and M. cassinii are smaller.
• Larva: Nymphs live 2 to 24 inches underground on tree roots and climb up trunks and posts to shed their skin when they emerge.
• Eggs: Laid in slits in twigs 3/16 to 7/16 inch thick; hatch in about 6 to 7 weeks.
• Damage: Stitched-looking slits in twigs, then brown, drooping or broken twig tips. Serious on young, small or newly planted trees.
• Timing: Late May into June in an emergence year; adults live 3 to 4 weeks.

Life cycle

Nymphs feed on root sap underground for 13 or 17 years. In April of the emergence year they dig up to about an inch below the surface, and they come out when the soil reaches about 64°F. They climb a tree or post, shed their skin and become adults, which live three to four weeks. About 10 days after emerging, females mate and lay eggs in twigs. Eggs hatch in six to seven weeks, and the tiny nymphs drop to the ground and burrow in to start the next 13- or 17-year cycle.

When to look: Only in emergence years for your brood, late May through June. Check a brood map before planting trees in the year before an emergence.

Periodical cicadas look-alikes

A few things get mixed up with it:

• Annual (dog-day) cicadas: Larger, with greenish wing veins, and they show up every year from July through September (Penn State).

How to control periodical cicadas

Cultural control

• Cover trees under 10 feet tall with netting before cicadas emerge and leave it on 4 to 6 weeks. Penn State and Purdue call for holes no bigger than 1/2 inch; NC State recommends 1/4 inch mesh or finer.
• Don't plant or transplant trees in the fall or spring before an emergence year in your area; NC State advises avoiding new plantings when a big emergence is expected within 2 to 3 years.
• NC State suggests pruning out damaged twigs after most eggs are laid but before they hatch; destroying those branches keeps many nymphs from reaching the roots.
• Large, healthy trees usually need nothing.

Biological control

• Birds and squirrels eat many cicadas, but Purdue says they can't keep up with a mass emergence.

Chemical control

Penn State says insecticides are not recommended for large, healthy trees. On small trees where netting isn't practical, sprays must be repeated every few days and can kill beneficial insects and mites, so netting is usually cheaper and works better for homeowners. Purdue calls pesticide use for cicadas controversial and recommends cultural controls. Use only products labeled for this use; the label is the law. For orchard or nursery situations, work with a licensed applicator; see our pesticide applicator license guide. Muthler Landscaping does not spray or apply pesticides.

Use only products labeled for this pest and this site; the label is the law. For trees, work with an ISA Certified Arborist. If you hire someone to apply pesticides, make sure they hold your state’s pesticide applicator license; the rules for each state are in our pesticide applicator license guide.

Prevention

• Look up your area's brood schedule before planning new tree plantings.
• Hold off on planting new trees until after an expected emergence, or net them.

When to call a pro

Usually not needed. Call an ISA Certified Arborist if a young or valuable tree was heavily flagged and needs corrective pruning after the cicadas are gone.

Related guides: Tree database: mature size and planting distance · Pennsylvania tree identification · Firewood rules by state · All pests and diseases

Questions about periodical cicadas

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