Homeowners and landscape professionals often overlook the subtle signs of cicada tree damage until the season’s chorus has faded and the evidence becomes impossible to ignore. While these large insects are generally harmless to humans, their feeding and egg-laying behaviors can inflict significant stress on trees, leading to aesthetic decline and, in severe cases, long-term health issues. Understanding the mechanics of this damage is the first step toward effective management and protection of valuable landscape assets.
Identifying the Source of the Problem
The primary culprits behind cicada tree damage are the female insects seeking suitable sites for their eggs. Unlike other pests that bore into the bark, cicadas require slits in the bark where they can deposit their eggs. This specific action, while part of the natural lifecycle of the insect, directly interrupts the tree’s vascular system, which is responsible for transporting water and nutrients throughout the structure.
The Mechanics of Bark Slitting
Female cicadas utilize their sharp, saw-like ovipositors to cut into small branches and twigs. These cuts are typically just deep enough to breach the bark and cambium layer. The tree responds to this wound by attempting to compartmentalize the damage, but the sheer volume of slits created during a single egg-laying session can overwhelm the tree’s natural defense mechanisms. This process not only creates open wounds but also severs the flow of sustenance to the affected limbs.
Visible Signs of Infestation
Recognizing the symptoms early can mean the difference between a full recovery and permanent decline. Visual inspection is the most immediate way to determine if a tree has been targeted. Look for the characteristic marks left by the insects, which appear as small, rectangular slits or dashes running parallel to the branch.
Flagging: The most obvious sign is the sudden wilting, browning, or death of the tips of branches, often referred to as "flagging." This occurs because the eggs block the sap flow, effectively cutting off the branch.
Sawdust and Frass: Small accumulations of fine sawdust or frass (insect waste) may be visible near the base of the tree or caught in the bark crevices.
Staining: The slits in the bark may appear darkened or stained, particularly if the tree has been dealing with the infestation for multiple seasons.
Long-Term Health Implications
While a healthy, established tree can often withstand a moderate cicada population, the cumulative effect of repeated attacks can be devastating. Each season of egg-laying creates new wounds on the tree. If these wounds are not given time to heal, they become entry points for pathogens, fungi, and other opportunistic pests. This secondary infection is frequently the ultimate cause of a tree's demise, rather than the physical damage itself.
Structural Vulnerability
As the upper branches die back due to cicada activity, the tree loses its canopy density. This creates a condition known as "dieback," where the tree becomes top-heavy and structurally unsound. Dead or weakened branches are significantly more likely to snap during storms or high winds, posing a safety risk to property and people below. The loss of foliage also reduces the tree’s ability to photosynthesize, further weakening its structural integrity over time.
Management and Prevention Strategies
Once the damage is visible, the window for effective chemical intervention is narrow and generally not recommended for large trees. However, there are proactive steps that can be taken to mitigate the impact and support the tree’s recovery. Focusing on overall tree health is the most reliable defense against cicada damage.
Deep Root Watering: Ensuring the tree receives adequate moisture, especially during dry periods, helps it allocate energy to healing wounds.
Mulching: Applying a layer of mulch around the base (without touching the trunk) conserves soil moisture and regulates root temperature.
