Vast populations of periodical cicadas will appear this spring in Ohio, West Virginia, Pennsylvania and Maryland after their 17-year underground life cycle comes to an end, said the U.S. Department of Agriculture in a report. To reduce cicada damage, homeowners have been advised to prune ornamentals and trees lightly.

The Forest Service calculates that this brood will be the largest occurring in those states since 1982. Periodical cicadas are different from annual cicadas, which appear by the end of summer. The Science Reference Services explains that the development of periodical cicadas is synchronized.

The US Department of Agriculture warned that a vast population of periodical cicadas will appear this spring in Ohio, West Virginia, Pennsylvania and Maryland. Credit: Daily Beast

“Almost all periodical cicadas grow and mature into adults at the same time, which is why we witness such huge groups of them every 17 or 13 years,” said the Science Reference Services from the Library of Congress.

Cicadas are recognized for a droning noise that they emit from early morning to late evening. According to the Department of Agriculture, males are responsible for that sound, as they try to attract mates. Charles Metz, from the Gardener Program in Maryland, said that the sound will begin in May and will last from 2 to 4 weeks.

It is not clear why periodical cicadas appear every 17 years. A theory proposes that it could be a survival strategy. If billions of these insects come out at the same time, their population would not be affected by birds and other predators.

How can cicadas survive during 17 years without even appearing in public?

Metz has explained that young cicadas called “nymphs” live underground, feeding on root fluids. They develop during 17 years in five different stages, growing from 5 millimeters (the size of an ant), to up to 50 millimeters.

When their life cycle turns 17 years old everything changes. The nymphs proceed to open an exit hole to the surface and show up at sunset, to find vegetation that allows them to molt into an adult, added Metz. A week after, they become “an active insect” and start singing and looking for mates.

Authorities have advised that people expecting to record an event during the cicada season, should be prepared for the background noise of billions of male cicadas singing at the same time, to keep their kind alive.

You should protect your trees

Periodical cicadas are not harmful to humans or other animals. Nonetheless, they can affect some trees like dogwoods, crabapple, oaks and maples since females lay eggs on its branches, said Metz from the Master Gardeners.

Branch undermined with cicada eggs are prone to die. However, most trees should recover after a few months. The Forest Service has recommended people to prune trees lightly, before the emergence of the insects.

“Small shade and ornamental trees can be protected by covering them with cheesecloth, finely woven netting or tobacco shade cloth. This physically prevents females from laying eggs in the twigs. Trees too large to cover may be sprayed with a contact insecticide,” said the Forest Service.

On the other hand, the Master Gardeners said that insect spray would make no sense since there are millions of cicadas. They recommend people to be patient since they only appear for a few weeks every 17 years and are “more annoying than dangerous.”

Source: U.S. Department of Agriculture