Homeowners and nature enthusiasts often pause when they hear the distinct, buzzing call of a cicada or witness the slow emergence of these winged insects from tree trunks. The question of whether these periodic visitors cause lasting damage to trees is a common concern, particularly during peak emergence seasons. The short answer is generally no, healthy trees remain unharmed by the feeding habits of adult cicadas and the egg-laying behavior of females. While the nymph stage lives entirely underground feeding on root sap, the above-ground lifecycle is designed for reproduction rather than destruction, meaning the visual evidence of insects clinging to bark or leaves rarely signals a fatal illness for established plants.
The Nature of Cicada Feeding Habits
Cicadas are often mistaken for locusts due to their size and noise, but their dietary needs are quite different. Adult cicadas primarily consume the sap from trees and shrubs using their specialized piercing-sucking mouthparts. This sap provides the necessary hydration and energy for the short adult phase, which typically lasts only two to six weeks. While the act of feeding does involve inserting a needle-like proboscis into the plant, the volume of sap consumed by a single insect is minuscule. Therefore, the physiological impact on a large, established tree is comparable to a human taking a small sip of water from a reservoir.
Impact on Different Tree Types
Not all trees react the same way to cicada activity, and the species of tree plays a significant role in the level of risk. Hardwood trees such as oak, maple, and fruit trees are the primary targets because they offer the right vascular structure for sap flow. In contrast, evergreen trees like pine and spruce are generally left alone, as their sap flow and needle structure are less suitable for the insects. Ornamental trees and shrubs with thin bark may experience more stress than robust forest giants, but even in these cases, the damage is usually cosmetic rather than fatal.
The Real Threat: Egg Laying
The actual harm to trees occurs not during the feeding phase but during the egg-latching process. Female cicadas use a saw-like ovipositor to cut slits into the bark of twigs, where they deposit their eggs. This incursion disrupts the flow of nutrients and water within the twig, often causing it to wilt, brown, and break off prematurely. While this sounds alarming, the damage is usually limited to the very tips of branches. A healthy tree can easily compartmentalize this damage, growing new buds the following season to replace the lost growth.
Thinning or wilting of the very ends of branches.
Visible slits or notches on small twigs where eggs were laid.
Increased susceptibility to secondary pests in the damaged areas.
Vulnerability of Young and Newly Planted Trees
The trees most at risk are not the ancient oaks in the forest but rather young saplings and newly transplanted specimens. These smaller plants do not have the energy reserves or the structural mass to withstand the loss of multiple twigs in a single season. For a young tree, the removal of a significant number of leaves and twigs can stunt growth or weaken the plant to the point of vulnerability. Protecting these fragile specimens with netting during a heavy emergence is a standard and effective practice recommended by arborists.
Secondary Pests and Diseases
While the cicadas themselves are not carriers of tree disease, the wounds they create can act as entry points for fungi or bacteria. If the ovipositor pierces the bark and leaves a small opening, moisture can become trapped, creating an environment for opportunistic pathogens. However, this is a secondary issue and is easily mitigated by proper pruning. Removing the affected twigs in the dormant season allows the tree to seal the wound and prevents any lingering pathogens from taking hold.
