By Megan Gross, Horticulture/Natural Resources Extension Agent, Colorado State University Cooperative Extension
I remember staring blankly out toward the old willow tree in our backyard. Its new sound intimidated me, and kept me far from my treehouse. Humming, drumming, strumming, thrumming. "Cicadas," my mom said. Ill play in the front yard, I thought.
I grew up in Ohio and, frankly, didnt expect to see so many cicadas here in Colorado. But, oh, are they ever here! Those having aspens or cottonwoods may already be acquainted with them. There are twenty-six species of cicada in Colorado.
Cicadas are harmless to humans, and do little if any injury while feeding on plants. Damage occurs when large numbers of certain species insert eggs into stems and trunks of trees and shrubs. This egg laying injury can cause some twigs to die back. According to a C.S.U. fact sheet on cicadas, no effective controls for Colorado cicadas have been developed nor are any likely necessary.
Other information Ive read indicates the common insecticide carbaryl (sold under the trade name Sevin) will knock them down. Gypsum bug sprayer, Don Donohue, says a hard spray from the hose will knock them down and perhaps drive them away. Birds and rodents may also help keep them in check as well as certain insect enemies such as the "cicada killer wasp" and "large cedar beetle".
You shouldnt have much trouble identifying the cicada, which can be up to two inches in length. They have fat bodies and transparent wings with black veins. The wings are held tent-fashion over the body. Theyre quite cute, I think.
Males make a long, shrill song that will last one to two minutes. This sound has been described as everything from an intense whining, to a sound like a circular saw cutting through a board, to "the most magical sound on earth".
Adults are present for about four to six weeks and are not known to eat. After finding the male with the best sound and mating, the adult females begin to lay eggs in slits they make in the trunks and branches of trees and bushes. After six or seven weeks, the eggs hatch and tiny ant-like nymphs drop to the ground, burrow beneath the soil surface, and spend the next two to seven years feeding on plant roots. Thats quite a long life cycle for an insect.
Photo: Judy Sedbrook
© CSU/Denver County Extension Master Gardener 2010
888 E. Iliff Avenue, Denver, CO 80210
Date last revised: 01/05/2010