Homeowners and arborists often look up in panic when they hear the telltale buzz of cicadas and then notice branches scattered across the lawn. While the insects themselves are harmless, the physical damage cicadas inflict on trees can be a serious concern, particularly for young or newly planted specimens. Understanding the mechanics of this damage, which species are most at risk, and how to respond can mean the difference between a healthy canopy and a tree that fails to thrive.
The Mechanics of Cicada Damage
Cicada damage is not caused by the insects chewing leaves or boring into wood. Instead, it is a direct result of the female’s reproductive process. To lay her eggs, a female cicada uses a saw-like ovipositor to cut slits into the bark of twigs and small branches. She then deposits her eggs into these slits. This incision disrupts the flow of nutrients and water within the branch, effectively girdling it. While a healthy, mature tree can often compartmentalize this damage and heal over the wounds, a young tree lacks the energy reserves to recover, leading to dieback that starts at the tip of the affected branch.
Which Trees Suffer the Most
Not all trees are targeted equally, and susceptibility varies based on the species and the age of the tree. Cicadas show a distinct preference for the xylem fluid of certain hardwoods, which provides the necessary nutrients for their developing nymphs. Fruit trees, such as apples, cherries, and peaches, are highly susceptible due to their soft, vigorous new growth. Nut trees like hickory and oak are also prime targets. Conversely, trees with thick bark or hardwoods like maple or ash are generally left alone, as the females cannot penetrate the bark to lay their eggs effectively.
Young Trees vs. Established Giants
The age of the tree is the single most significant factor in determining the severity of the impact. Newly planted saplings, typically those with a trunk diameter of less than half an inch, are at the highest risk. The death of terminal shoots on these young plants can stunt their growth permanently, causing them to become bushy or develop a forked trunk as side branches take over. In contrast, established trees with a diameter of four inches or more usually survive cicada activity with minimal long-term harm, despite the aesthetic damage to their branches.
Identifying the Signs of Infestation
Recognizing the damage is the first step in managing the problem. The most obvious sign is the presence of dead or dying twigs at the ends of branches. These dead shoots, often referred to as "flagging," will appear brown and withered, contrasting sharply with the green, healthy foliage below. If you inspect the branch closely, you may see a small, linear incision where the eggs were inserted. You might also notice small, rice-like nymphs emerging from the slits if the damage occurred recently.
Management and Prevention Strategies
Once the damage is visible, it is too late to save the affected twigs. The primary method of management is therefore preventative and focuses on protecting vulnerable young trees during the emergence period. One effective solution is to cover the tree with fine-mesh netting, such as tulle, draped over the canopy and secured tightly around the trunk. This physical barrier prevents the females from accessing the branches to lay their eggs. For high-value specimen trees, a professional arborist may recommend specific insecticidal trunk treatments, though this is rarely necessary for landscape settings.
