When cicadas arise from underground in their 13- and 17-year life cycles, they emerge by the tens or hundreds of thousands and can cause significant damage to trees that they infest. However, the insects do not cause harm to humans beyond the annoyance of their number and noise.
Cicada Damage to Plants and Trees
These 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 nursery know the life cycles of periodical cicadas in there are and not plant young trees or shrubs in a year or two before expected emergence.
Although damage to mature trees may appear extensive after having hundreds or thousands of cicadas living on them, there is generally little lasting damage.
The nymphs that live beneath the ground during the majority of the cicada's life cycle can also cause damage, however, as they feed on the roots of the trees, potentially stunting their growth.
Cicada Harm to Humans
Cicadas do not cause any harm or hazard to humans, as they 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 will generally be little more than the feeling of a pinprick.
Natural Cicada Control
- Many animals feed on these pests, however, because they emerge in such high numbers, it is virtually impossible for them to all be attacked or consumed.
- 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 eat cicadas.
Non-Chemical Cicada Control
- Young vines/vineyards. cover the trunks of the young vines with aluminum foil or other covering to keep nymphs from climbing up.
- 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.
- Do not plant trees within the year or two prior to the periodical cicadas' regional year of emergence.
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; this is approximately 7-10 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, read and follow all label directions.