The 17 year cicadas are coming this year

Charlie Metz
Frederick County Master Gardener Program

In case you haven't heard yet, the cicadas are coming this year. In the next few months you will be hearing about the impending emergence of the 17 year cicada, mistakenly called 17 year locusts. If you don't remember the last outbreak, or if you are new to this area, you need to know a few facts about this periodic phenomenon.

Cicadas are large, plant-feeding insects. They have clear wings and are known for making a very loud noise. When tens of thousands of cicadas are singing at the same time the sound is quite loud and annoying. Be prepared for about 2 to 4 weeks of this sound beginning in May.

Although it is not entirely clear why this insect comes out every 17 years, scientists believe it has something to do with survival. Since billions of cicadas emerge at about the same time, it is impossible for birds and other predators to make a dent in the population. Yes, the birds have their fill of cicadas, since this insect is a rather cumbersome flier. But how much can one bird eat in a month?

Cicada juveniles are called "nymphs" and live underground, sucking root fluids for food. During the 17 years, they go through 5 different stages, growing from the size of an ant to almost as large as an adult. (25-50mm). In the spring of the 17th year, the nymphs construct an exit hole to the surface. These holes are about ½ inch in diameter. The insect emerges at sunset, finds some vegetation, and molts into an adult. It takes about a week before the cicada becomes active. This is when the singing begins.

It is only the males that produce the "songs". The males have a pair of tymbals, or ridged membranes that they vibrate to make a noise that only a female cicada could like. This song is sung to attract her to mate. A few cicadas singing is tolerable, but during the peak time millions of male cicadas will be working hard to fulfill their destiny. Be prepared for a background whistling drone that will be around for a few weeks. If you have a video camera and want to record an event like a birthday party or outdoor wedding, be prepared to possibly be drowned out by the background noise.

Cicadas do not cause harm to humans or animals. Sometimes pets will trap and try to eat them. In response the cicada will buzz and probably cause the animal to drop it, but otherwise causes no harm.

Periodical cicadas do some damage to trees. After mating, the female lays eggs on outside branches of many trees such as dogwood, crabapple, oak, and maple. At the point where the eggs are laid, extending to the tip of the branch, the branch will usually die. When hundreds of cicadas invade a tree, the dead branches will show up about a month later. Although unsightly, this damage is minor and the tree will recover. However, newly planted trees could possibly be killed if enough damage is done. A simple covering with a screening material like cheesecloth will prevent damage to small trees.

Spraying for this insect is really a waste of time. There are so many cicadas that it is virtually impossible to make a dent in the population. Since this insect is only around for a few weeks every 17 years, and since it is more annoying than dangerous, it is probably best to just put up with the noise and wait for it to come to an end.