Cicadas comprise a very large family of flying insects in the Hemiptera order (true bugs). There are some 3,000 species in this Cicadoidea superfamily, but only a relatively few species are the common pests seen across much of North America. What unites the species are the exceptionally loud song the insects make, as well as the unique reproductive cycle.
Found in every continent except Antarctica, cicadas from the Cicadidae family are usually fairly large insects, 1 to 2 inches long, with large eyes set wide apart and large transparent wings. As distinctive as the appearance is, the most telling characteristic is a piercingly loud song, produced by the rapid muscular vibration of a unique organ that resonates through membranes into a hollow abdomen cavity. The particular mechanism of this male mating song varies from species to species, but it is always quite loud. Sound measurements have put the mating song as high as 120 decibels, comparable to that of a chainsaw or nearby jet take-off. Cicadas produce the loudest natural sounds of any insect, and if you see a large flying insect with transparent wings where such loud songs occur, you have spotted a cicada. Cicadas often appear in late July or August.
There are many hundreds of common species of cicadas, most of which have life-cycles that run 2 to 5 years. Most famous, though, are the periodic cicadas of the Magicicada genus, which appear in large numbers every 13 or 17 years. While annual cicadas that appear every year rarely have numbers sufficient enough to cause major damage, the huge swarms of tens of thousands of periodic cicadas, when they arise from underground in their 13- and 17-year life cycles, can cause significant damage to the trees they infest. In fact, some experts believe that the legendary biblical description of locust plagues may have been based on cicada infestations. However, these insects do not cause harm to humans beyond the annoyance of their numbers and their noise.
These insects spend most of their life cycle underground, feeding on roots of deciduous trees. Every 13 or 17 years (depending on region) the nymphs of periodic cicadas emerge from underground, where they pursue a short reproductive cycle of only about 4 to 6 weeks. Once eggs laid, the insects vanish for the next 13 or 17 years.
Cicada Damage to Plants and Trees
Periodical cicadas may attack virtually any tree. The only ones that are fairly safe from their numbers are those that excrete sap, such as pine trees.
Some trees and plants that are most likely to incur damage are apple trees, young grapevines, small trees, and shrubs. Because of this, it is recommended that those who own or plant orchards or nurseries know the life cycles of periodical cicadas in the area, and refrain from planting and young trees or shrubs in the year or two before an expected emergence.
Although damage to mature trees may appear extensive due to the impact of having hundreds or thousands of cicadas living on them, there is generally little lasting damage. However, the nymphs that live beneath the ground during most of the cicada's life cycle can also cause damage as they feed on the roots of the trees, potentially stunting their growth.
Non-Harmful to Humans
Cicadas do not cause any harm or hazard to humans, other than the annoyance of the loud mating song. These insects normally do not bite, sting, or attack people. If a cicada is handled for too long, it may attempt to feed on a person's hand, but they are not poisonous or known to transmit disease, so the attempt is little more than the feeling of a pinprick. For some people, the intensely loud song can be emotionally stressful for the few weeks the insects are prevalent.
Many animals feed on these pests, however, because cicadas emerge in such high numbers, it is virtually impossible for significant numbers to be attacked or consumed by natural predators.
Cicada predators include birds, such as grackles and crows, and fish, which will gorge on the insects. In addition, parasitic wasps, flies, predatory mites feed on the eggs, and birds and cicada-killer wasps feed on adults.
Even humans have been known to dine on cicadas. According to Dr. Gene Kritsky, Professor of Biology at the College of Mount St. Joseph, "Periodical cicadas are best eaten when they are still white, and they taste like cold canned asparagus. Like all insects, cicadas have a good balance of vitamins, are low in fat, and, especially the females, are high in protein." Early Native Americans and John the Baptist were said to have dined on cicadas.
Non-Chemical Cicada Control
A variety of non-chemical controls may help prevent damage to plants:
- On young vines, cover the trunks of the vines with aluminum foil or other covering to keep nymphs from climbing up.
- On small or young trees, wrap the branches loosely with cheesecloth or other mesh cloth. This will keep females from being able to drill into the branches to lay their eggs. Apply the cloth or screening as soon as cicadas emerge and leave it on for about a month, or until the cicadas are gone.
- Knock the insects off of small trees and shrubs with blasts of water from a garden hose.
- Do not plant trees within the year or two prior to the predicted emergence of periodic cicadas in your region. Established trees are usually immune to lasting damage.
Chemical Control of Cicadas
Because the periodical cicadas are so numerous, pesticide application is rarely practical. However, there are some insecticides registered for use on deciduous shrubs, fruit, nut, and shade trees that can provide some protection. The first application should be made prior to egg laying—approximately 7 to 10 days after the male periodical cicadas start their singing. It may be necessary to repeat the application to keep the female cicadas from laying her eggs. When using any pesticide, make sure to read and follow all label directions.