What can central Ohio gardeners expect from the once-in-a-generation emergence of Brood X of the periodical cicada in the next couple of weeks? To answer that question we must understand what the periodical cicada is, what it feeds on, where in the landscape we can expect to find them and its life cycle.
The periodical cicada, or 17-year cicada, is an insect with a very long life cycle that takes 17 years to get from the egg stage to the adult stage. Many times the periodical cicada is mistakenly referred to as a locust but is not related to and bears no resemblance to locusts, which are a type of grasshopper.
The periodical cicada spends 17 years underground in the nymph stage feeding on the roots of many different species of trees. This feeding causes no known damage to the host.
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After 17 years feeding underground, periodical cicadas emerge once the soil temperature reaches 64 degrees (it’s about 60 degrees right now) and then sing loudly in search of a mate before completing mating, laying eggs for the next generation and then dying.
Potential for damage
Adult periodical cicadas lay their eggs in small branches of trees by inserting a sharp egg-laying structure called an ovipositor by slitting the branch in order to deposit their eggs. Once these eggs hatch, the nymphs fall to the ground and burrow into the soil to feed for 17 years.
The scars caused by these slits often weaken the small branches, which then break and hang on the tree causing damage called flagging — owing to the hanging branch tips which flutter in the wind. These dead branch tips rarely cause harm to the long-term health of the tree. Young and newly planted trees, including fruit trees, however, are most at risk for damage because of their size. Small trees might lose entire branches because of damage from large numbers of eggs deposited by periodical cicadas.
Periodical cicadas do not seem to lay their eggs in shrubs and other woody ornamental plants. Vegetable plants, flowers and other perennial plants also are safe from the periodical cicada. Periodical cicadas do no sting or bite and are not poisonous if consumed by pets or kids engaged in double-dog dares.
Mature trees are hosts
Unless your property contains or is located close to trees that are at least 20 years old, you likely will not be visited by the periodical cicada, as they do not spread far from their food source.
Gardeners who live in older homes with lots of older, well-established trees in the landscape are likely to see the greatest number of periodical cicadas. The greatest numbers of the insects will be found near parks, cemeteries, forests and other wooded areas with older, well-established trees.
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Protecting young trees
Gardeners with young or small trees in close proximity to stands of older trees may choose to protect the young trees from egg-laying by the periodical cicada by wrapping the foliage with netting.
Only netting made of nylon with mesh no larger than one-half inch will provide adequate protection. The netting must cover the foliage of the entire tree and be tied at the trunk of the tree to prevent the cicadas from gaining access to the branches of the tree. The netting should not be tight enough to constrict normal growth of the tree.
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If, however, you discover cicadas in trees, it’s best to leave them alone. They really are more of a nuisance or oddity than an actual threat to the health of 99% of trees in the environment.
So relax, besides being an oddity of nature, periodical cicadas cause very little, if any, damage. And mark your calendars for May 2038 when this year’s crop of nymphs will emerge from the ground as adults.
Mike Hogan is an associate professor at Ohio State University and an educator at the OSU Extension.