Homeowners and nature enthusiasts often find themselves asking whether the loud, buzzing presence of cicadas poses a threat to their trees. The short answer is that adult cicadas do not kill trees, but the females’ egg-laying behavior can cause cosmetic damage to young or thin-barked species. Understanding the difference between a healthy ecosystem and genuine stress helps clarify the relationship between these insects and the health of your landscape.
The Lifecycle and Feeding Habits of Cicadas
Most of the concern surrounding cicadas stems from a misunderstanding of their lifecycle. Adult cicadas live for only four to six weeks, a brief period dedicated to mating and egg deposition rather than feeding on tree sap. The majority of a cicada’s life is spent underground as a nymph, where they feed on xylem sap from tree roots. This underground phase can last 13 or 17 years, depending on the species, but it causes minimal harm to the root system and does not girdle or kill the tree.
Adult Feeding vs. Nymph Feeding
Adult cicadas possess straw-like mouthparts designed to sip plant juices, but they rarely utilize them for feeding. Their primary focus during the brief above-ground phase is reproduction. In contrast, the nymphs underground consume root sap, which is a necessary part of their development. While this might sound detrimental, the volume of sap taken is insignificant to a healthy tree’s overall vitality, making the nymph stage largely benign.
Oviposition Damage: The Real Cause for Concern
The actual damage occurs when female cicadas use their saw-like ovipositors to cut slits into the bark of twigs. They deposit their eggs into these slits, which disrupts the flow of nutrients between the leaves and the roots. This process, known as "flagging," causes the affected twig to die and fall to the ground. While this creates a brown, withered appearance, it is rarely fatal to the tree and primarily affects the aesthetic value of the foliage.
Which Trees Are at Risk?
Not all trees suffer the same consequences from cicada activity. Young trees, saplings, and species with thin bark are the most vulnerable to significant flagging. Conversely, large, mature trees with thick bark and robust growth are generally resilient. Their size allows them to withstand the minor damage without any long-term decline in health or structural integrity.
Protecting Your Landscape
If you live in an area expecting a heavy emergence, proactive protection is possible. Wrapping young trees in fine mesh netting during the cicada season prevents females from accessing the branches to lay eggs. This physical barrier is the most effective method to preserve the appearance of new growth and prevents the stress of excessive flagging.
Long-Term Tree Health
Healthy soil and proper watering are the best defenses against any pest or stressor. A tree that is already struggling due to drought or disease will have a harder time recovering from cicada damage. By ensuring robust root systems and adequate nutrition, you allow the tree to compartmentalize the injury and continue thriving despite the presence of the insects.
