March 17, 2004 | By: Laura Skillman
PRINCETON, Ky.

After nearly 17 years of living underground, the periodical cicada is set to emerge this spring across the state and several surrounding states as well.

The insect gets its name because of the large adult emergences or broods that occur at predictable intervals. There are 13-year and 17-year periodical cicadas as well as annual cicadas but the two types are easily distinguishable, said Doug Johnson, an entomologist with the University of Kentucky Cooperative Extension Service.  With the exception of a few small pockets west of the Mississippi River, periodical cicadas are found nowhere else in the world except the eastern United States.

Periodical cicadas will start to emerge sometime between late April and early June. No one really knows how the cicadas do this, but those in an individual brood all emerge at about the same time, Johnson said. They burrow to near the soil surface then, in a course of one to two nights, emerge. If it is wet they will make little mud chimneys similar to a crawfish chimney.

They go to the first vertical object they can find where the juvenile skin will split and the adult will emerge. The adult is soft when it emerges but at soon as the wings and body touch oxygen it will begin to harden. They will remain there with their wings spread until they harden.

The periodical cicada has a black body, red eyes and clear wings with orange veins. They are about 1.5 inches long. The annual cicada is larger, 2 to 2.5 inches, has green eyes a green to black body and clear wings with green veins. The annual cicadas usually appear in July to September.

The singing noise of the cicada can be quite loud where a large number of the insects have emerged. This noise is made by the males to attract females. The adults will live for about a month or two.

“For the vast majority of people other than fear and irritation, they are nothing more than a curiosity,” he said.

Large, mature trees may be covered up with the insects, but the tree is not in any danger unless it has been compromised by something else.

The types of situations were they can cause problems are orchards and ornamental production. They also like to lay eggs in grapes. In the home landscape the only real concern is with new trees.

Injury occurs to trees, shrubs and other plants when the female cicada splits the bark on pencil-sized twigs and lay eggs inside the wounds. A female does this on a number of occasions and many, many females are doing this.

For large trees, you may lose this year’s spring growth and they may look bad but it will have no impact on their longevity, Johnson said.

For fruit bearing trees and ornamental trees, producers could see reduced production this year. In ornamental plants a producer could lose last year’s growth as well because of the need to prune out damaged limbs.

The second way these insects can cause damage is when the eggs hatch and nymphs fall to the ground where they will burrow in and feed on the roots during their long stay underground, Johnson said.

With large, mature trees that’s not an issue. But for fruit trees, it puts an additional

burden on the tree’s ability to bear or hold fruit. For the first four or five years, it’s probably not a big deal, but in the latter years it could be a problem. On ornamental trees that are dug and removed some cicadas may survive the process but shouldn’t be much of a problem, he said.

 For homeowners, there is no need to do anything to combat the insects for large, mature trees. For smaller trees and fruits, they may want to bag them with cheesecloth to keep the insects out. This works well for small trees.

Another option is to try prune out the egg laying damage every few days.

“Don’t leave the pruned material laying on the ground under the tree,” he said. “Get rid of it or you haven’t helped the situation.”

The third option is to treat with insecticides. They will kill the insect, but there are millions of them. If it is a heavy infestation, a person could be spraying every two or three days. If it is a commercial business with a lot of money tied up in stock, they may be spraying daily.

There are a number of products that are available and a good garden store should be able to help a homeowner pick out something that is appropriate for their landscape. UK also has two publications available on periodical cicadas. Visit the college web site at www.ca.uky.edu to find the publication or contact a local office of the UK Cooperative Extension Service.

Johnson said there are a number of myths surrounding this insect.  Sometimes cicadas are called locusts, but locusts are very different. At least some people believe that this confusion goes back to early settlers when many people went to the northern woodlands for religious reasons. When these insects came out, they had never seen them before but had read the biblical accounts of the plagues of locusts in Egypt. So the theory is that these people mistook the cicada for these ancient locusts.

Another myth is that whatever fruit this insect feeds on is poison and that is false.

“If they are worried about that, they can bring me their fruit and we’ll find a place for it,” he said. “There are a lot of stories about them because they are so rare, they come out so quickly and then they are gone.”

It is hard to know where there will be a large infestation. But these periodical cicadas can’t come off anything that is less than 17 years old, Johnson said.  In areas where there are old growths of trees, there will probably be a lot of them while other places may only hear them singing in the distance.

Contact: 

Source: Doug Johnson, 270-365-7541, ext. 214