February 6, 2002 | By: Laura Skillman
PRINCETON, Ky.

Kentucky residents living west of Interstate 65 will hear loud racket coming from the trees beginning in late April as a brood of the 13-year periodical cicada comes calling.

"They make a lot of noise but they are completely harmless to humans and animals," said Doug Johnson, entomologist with the University of Kentucky Cooperative Extension Service.

These often misunderstood insects cannot sting and are not known to cause any diseases. They are sometimes mistakenly called locusts. This misinformation may stem from an incorrect assumption by early settlers that these insects, which come out in hordes overnight, were the grasshoppers or locusts referred to in Biblical accounts. But these insects are not related.

Another brood of periodical cicadas, a 17-year brood, will emerge from the ground across the state in 2004.

"This is important to people setting new fruit trees and new grape vines or have small plants," he said. "Periodic cicadas are an interesting insect but in terms of full-size, mature trees, they are only a curiosity and are not a problem. They appear to damage the tree, but it is of no real significance. For the small tree, especially trees bearing a fruit load, they can be very devastating. They also attack grapes and a large number of other plants."

These insects will emerge from the group beginning in late April or early May and the adults will be there for about 60 days. The damage is done to plants when the female slits the bark to lay her eggs inside. So on any tree you can count on losing one year, maybe two years' growth.

"It's not a killing sort of thing but if you are looking to shape trees, you are going to end up doing a lot of pruning," Johnson said. "For trees with a heavy fruit load, it will be detrimental to that fruit load if they lay a lot of eggs."

"For most of the rest of plants, they will be a curiosity, nothing else," he said. "They will make a lot of noise and where they come out in large numbers they will be rather startling, but they are completely harmless to people."

The adults only live about two months. They emerge from the ground as mature juveniles and attach themselves to an upright surface. The back splits and the adult comes out and remains there for a several hours to dry out. Then, the color will come and they will mate after a couple days. After mating the male dies and the female looks for places to lay her eggs, then she will die.

These cicadas look different from the dog days or annual cicadas that do not come in the large numbers as the periodical cicadas. The periodical cicada has red eyes and clear wings with orange veins. The annual cicadas have green eyes and green veins in clear wings and are much larger.

The eggs will hatch about six weeks after being laid and tiny nymphs will drop to the ground and burrow to the root system where they will remain until time of maturity. They feed on the sap of the roots.

For commercial fruit growers, there are sprays available to help control the cicada or they may choose to do nothing. If there are not many, they can get pretty good control with normal products in their spray schedule. But if there is a large number, then they will have to use synthetic pyrethroids to get good control but that can cause a resurgence in mites and can result in a severe mite problem.

Another option is to prune off the twigs that have eggs on them but that can mean pruning out a lot of fruit, Johnson said.

For the home gardener who has only a few small trees, rather than spraying he or she would be better off pruning or getting a cheesecloth netting bag and bagging the whole tree during the time of heavy cicada infestation. They can also cover grapes and other delicate plants.

"They can't just cover them up with anything, it needs to be something that can breath and let some sunlight in," Johnson said.

Covering is probably the best option for home gardeners because it keeps the cicadas off the plants and keeps the nymphs from falling to the roots, he said.

For more information on the periodical cicada, go to the entomology department's web site at: http://www.uky.edu/Agriculture/Entomology/enthp.htm and select "Help Pest Problems." The information is in EntFact 446.

Contact: 

Doug Johnson, (270) 365-7541