Homeowners and nature enthusiasts often wonder about the feeding habits of the loud, emerging insects known as cicadas. The short answer to whether cicadas eat trees is that they do not consume wood or leaves in the way a caterpillar or a beaver would. Instead, these insects utilize a specialized straw-like mouthpart to sip fluids from the vascular system of a tree, a process that is more parasitic than culinary.
The Feeding Mechanism of Adult Cicadas
During their brief adult stage above ground, cicadas are primarily focused on reproduction rather than sustenance. The males produce the characteristic buzzing sound to attract females, while both sexes rely on energy reserves accumulated during their long immature phase. To stay hydrated, they use their needle-like proboscis to pierce the bark of twigs and small branches to reach the xylem fluid, which is rich in water and nutrients. This feeding behavior is generally harmless to mature trees, though it can cause cosmetic damage to young or thin-barked saplings.
The Real Impact: Nymphs Underground
The life stage that truly interacts with the roots of a tree is the nymph. For 13 or 17 years, depending on the species, these nymphs live deep in the soil, feeding on root sap. They use their robust forelegs to tunnel through the earth and their mouthparts to tap into the roots of various plants and trees. While this constant sucking can stress a young tree by depriving it of vital nutrients, established landscapes usually possess enough vigor to withstand the assault without long-term harm.
Root Damage and Tree Stress
Significant damage is most likely to occur in nursery stock, newly planted trees, and shrubs. The removal of root mass and the constant pruning of root tips by cicada nymphs can impede a tree’s ability to absorb water and minerals. Signs of stress might include wilting, yellowing leaves, or reduced growth the season following a cicada emergence. Protecting these vulnerable specimens with a layer of mulch or a physical barrier can help mitigate the impact until the cicadas complete their cycle.
Do Cicadas Kill Trees?
Healthy, mature trees are remarkably resilient and rarely die as a direct result of a cicada emergence. The energy expended by the tree to repair the tiny wounds and regenerate root tips is typically offset by its natural vitality. However, experts warn that cicadas can act as a compounding stressor for trees already weakened by drought, disease, or poor soil. In these cases, the additional pressure from root feeding and egg-laying can push a fragile specimen to decline.
Egg-Laying Slits
Female cicadas use a sharp, saw-like ovipositor to cut slits into the bark of small branches to deposit their eggs. This process, known as "flagging," interrupts the flow of nutrients between the leaves and the roots. While the tree usually compartmentalizes this damage and heals over the wounds, heavy infestations can lead to branch dieback. Pruning these damaged branches after the adults have died off is usually sufficient to restore the tree’s health.
Ecological Perspective and Benefits
Though the relationship between cicadas and trees might seem parasitic, the insects play a vital role in the ecosystem. Their emergence aerates the soil, and when they die, their bodies act as a vital source of nitrogen for the soil, effectively fertilizing the trees they once fed on. This natural cycle has been occurring for millions of years, and trees have adapted to survive, and in some cases thrive, alongside these periodic visitors.
Management and Coexistence
Because cicadas are a natural and periodic part of the environment, chemical intervention is generally discouraged. Spraying insecticides can harm beneficial insects like bees and butterflies, disrupting the local ecosystem far more than the cicadas themselves. The most effective strategy for gardeners is patience and protection. covering vulnerable saplings with fine mesh netting during the emergence period or simply waiting out the few weeks of adult activity ensures that your landscape survives the event without unnecessary chemical use.
