Cicadas are insects known for their periodic emergence, prompting questions about their effects on the environment. Understanding their interactions with plants, people, and pets helps clarify their overall impact.
Impact on Plants
Female cicadas affect plants primarily through oviposition, their egg-laying behavior. After mating, a female uses an ovipositor to create small slits in tree branches (typically 1/4 to 1/2 inch in diameter), depositing 10 to 25 eggs per slit. She can lay hundreds of eggs across multiple branches.
This process often leads to “flagging,” where branch tips wilt, turn brown, and may break off. While dramatic, established, healthy mature trees generally sustain minor damage and recover readily. Flagging acts as natural pruning and typically poses no long-term threat to tree vitality.
Young trees, recently planted specimens, and shrubs with slender branches are more susceptible to significant harm. Extensive egg-laying on these smaller plants can lead to severe branch dieback, canopy loss, or even mortality. Common hosts include deciduous trees like oak, maple, fruit trees, and dogwood, while conifers like pine are generally avoided.
Cicada nymphs feed underground on tree roots for years before emerging. While this root feeding typically causes no discernible harm to mature trees, prolonged feeding could disrupt nutrient uptake and weaken the vigor of young or already stressed trees, making them more vulnerable to other environmental stressors.
Concerns for People and Pets
Cicadas do not possess stingers or biting mouthparts. While they have piercing-sucking mouthparts for feeding on plant sap, they generally do not bite defensively. Any rare instances of a cicada probing human skin are accidental, as they mistake it for a plant surface.
The most common concern for people during a large cicada emergence is the noise. Male cicadas produce loud buzzing sounds to attract mates, which can reach volumes of 90 to 110 decibels, comparable to a lawnmower or power tools. This persistent noise can be annoying and, for individuals with sensory sensitivities, potentially overwhelming or even painful.
Cicadas are not toxic or poisonous to pets. However, if pets consume large quantities, the hard exoskeletons can be difficult to digest, leading to gastrointestinal upset such as vomiting, diarrhea, or abdominal pain. There is also a slight risk of choking, particularly for smaller animals, or of ingesting pesticides if the cicadas have been exposed to treated areas.
Some individuals with shellfish allergies may experience an allergic reaction if they consume cicadas, due to shared proteins. Additionally, during some emergences, tiny itch mites that feed on cicada eggs can become abundant and cause itchy welts on humans and pets if they fall from trees and bite.
Ecological Contributions
Cicadas contribute to ecosystem health. The nymphs spend years burrowing through the soil, creating extensive networks of tunnels. This natural tunneling aerates the soil, improving its structure, enhancing water penetration, and promoting healthier root growth for plants.
Upon their emergence and eventual death, cicadas return a significant amount of biomass to the environment. Their decomposing bodies enrich the soil with essential nutrients, including nitrogen and carbon, functioning as a natural fertilizer. This influx of nutrients supports plant growth and contributes to the overall fertility of forest ecosystems.
Cicadas also serve as a substantial food source for a wide array of wildlife. During mass emergence events, they provide a high-protein feast for birds, small mammals, reptiles, and other insects. This abundance can lead to a temporary increase in predator populations and can even influence the breeding success of some species, a phenomenon sometimes referred to as predator satiation.