Folklore has it that every 17 years, cicadas—also known as 17-year locusts—emerge and inundate an area.

This is the year for the Northeast, including Connecticut, Maryland, North Carolina, New Jersey, New York, Pennsylvania and Virginia.

Known generically as periodical cicadas, the insects in different regions are not synchronized and may emerge in different years, according to a University of Michigan website.

Cicadas also are patchy, so they won't be found in large numbers throughout each state.

Although the insects prefer wooded areas, they can do significant damage to orchards and vineyards—especially newly planted ones, according to Virginia Tech entomologists.

Periodical cicada actually refers to three species of seventeen-year cicadas and three species of the more southerly thirteen-year cicada.

There also are 30 broods, most separated geographically.

Not all are large enough to be significant.

Brood X, the most important numerically, last appeared in 1987.

Brood II is the one that is appearing this year.

Cicadas spend most of their life underground as nymphs, feeding on xylem of tree roots.

During the final year, they crawl up tree trunks or other structures, shedding their skin and emerging as adults.

Only the female feeds.

Adults are active for about six weeks after emergence.

Females create 1- to 4-inch slits in twigs and lay eggs in the opening in groups of 10-25.

They may lay up to 500 eggs.

The main damage to fruit trees and vines occurs during ovipositioning, or egg laying, in the twigs.

The region around the wound dies, which can damage the tree structure, especially in young blocks.

You may want to delay planting a new block if emergence is expected within one to two years, according to Virginia Tech entomologists.

Nymphs, or immatures, also can cause root damage during feeding. Adults may feed through bark, causing oozing of sap.

In pears, the wound can provide an entryway for the fire blight bacterium.

Entomologists recommend monitoring when adult emergence is expected.

There are no thresholds, so they recommend treating when masses of cicada begin to appear in orchards.

Several pesticides are registered.