A periodical cicada emergence is a singular event: a spectacular, noisy spectacle of nature. When the last buzz fades, it’s natural to survey the landscape and attribute any subsequent tree damage—especially the signature brown, drooping branch tips, or “flagging”—to these recent visitors.
The problem? This easy assumption can become the single greatest threat to your landscape’s health.
For every time the diagnosis is “cicadas,” there are several other times the issue is a potentially lethal wood-boring insect, an aggressive fungal canker, or critical mechanical damage near the base. While cicada damage is a self-limiting annoyance, overlooking a deadly borer or a spreading disease because you chalked it up to the buzz can cost you an entire mature tree.
This guide will provide a clear, arborist-grade distinction between the harmless evidence of cicadas and the genuine threats hiding in your canopy, allowing for an accurate diagnosis and timely action.
Part 1: Establishing the Baseline—What True Cicada Damage Looks Like
To correctly identify an imposter, you must first be intimately familiar with the real deal. Cicadas do not feed on leaves or bark; the damage they cause is strictly for reproduction.
The Anatomy of a Cicada Wound
Female cicadas use a sharp organ called an ovipositor to slice into young, pencil-sized twigs (roughly 1/4 to 1/2 inch in diameter) to create a protective pocket for their eggs.
- The Appearance: They don’t make one cut, but rather a long, continuous line of gashes along the twig. The resulting wound looks like someone ran a coarse saw blade along the branch, leaving the bark pushed up and splintered at the edges.
- The Result: This damage compromises the twig’s vascular system. The section beyond the cut dies, turns brown, and droops—the phenomenon arborists call flagging.
The Bottom Line: On a healthy, mature tree, this is a form of natural pruning that is rarely fatal. It looks alarming for a few weeks, but the tree easily compartmentalizes the injury. If the tree is young or stressed, however, the damage can be significant.
Best Amazon Picks
Part 2: The Lethal Imposters—Insects Mistaken for Cicadas
Misdiagnosis in this category is the most dangerous because you are missing a threat that is actively killing your tree.
1. Wood-Boring Insects (e.g., Emerald Ash Borer, Asian Longhorned Beetle)
Borers are the number one cause of insect-related tree mortality. Unlike cicadas, which slice to lay eggs, borers tunnel deep into the tree to feed on the vital cambium and xylem.
- The Confusion: Both can cause branch dieback and flagging.
- The Critical Distinction: Look for exit holes and frass (sawdust).
- Cicadas leave long, splintered surface slits.
- Borers leave distinct holes that go deep into the wood. These are often perfectly round or, in the case of the notorious Emerald Ash Borer, D-shaped.
- If you see fine sawdust (frass) near a hole or accumulating at the base of the tree, it is absolutely a borer and demands immediate professional attention. Cicadas do not produce sawdust.
2. Twig Girdlers and Pruners
These beetles cause damage that can fool even experienced gardeners. The female chews a perfectly clean notch completely around a small branch (girdling it) before laying her egg in the portion that will fall off.
- The Confusion: The result is exactly the same as cicada damage: brown, hanging tips that eventually snap off and fall.
- The Critical Distinction: Pick up a fallen branch.
- If the broken end is jagged and runs through splintered egg slits, it’s a cicada.
- If the end is cleanly cut and smooth, as if severed by a tiny, precise saw, it’s a twig girdler or pruner.
Part 3: Beyond Insects—Diseases and Mechanical Wounds
Not every wound is caused by an insect. Assuming cicadas are the problem can cause you to ignore fungal infections or life-threatening injuries to the trunk.
1. Canker Diseases (e.g., Cytospora, Nectria)
A canker is a localized area of dead bark and underlying wood, typically caused by fungi, that attacks a stressed or wounded tree.
- The Confusion: A canker on a branch will disrupt the flow of water and nutrients, causing the branch tip to flag and die—just like cicada damage.
- The Critical Distinction:
- Cicada damage is a simple physical cut into the twig.
- A canker appears as a sunken, discolored, or swollen patch of bark on a larger branch or trunk. It may also show signs of oozing sap or resin. The dieback originates from this discolored patch, not from a slit at the very tip.
2. “Lawnmower Blight” (Trunk Damage)
This is one of the most common causes of slow tree decline and death in residential areas. Repeatedly striking the base of the tree with a lawnmower or string trimmer destroys the vital vascular tissue.
- The Connection: This damage creates severe, invisible stress, which eventually manifests as overall decline and dieback in the canopy. A homeowner sees the dead branches during a cicada year, blames the bugs, and ignores the severe, ongoing injury at the trunk that is slowly killing the entire tree.
- The Critical Distinction: Check the base of the trunk. If there is any missing, chewed, or repeatedly scarred bark at ground level, that is the primary problem, not the cicadas in the canopy.
Your Tree Diagnosis Checklist
Before you write off tree damage as temporary cicada inconvenience, run through this simple checklist. The more specific you can be, the better chance your tree has.
| Diagnostic Question | If YES, it’s Likely… | If NO, look for… |
| Location: Is the damage on tiny, pencil-sized twigs at the outer canopy? | Cicadas or Twig Girdlers. | Borers, Sapsuckers, Cankers, Mechanical Damage. |
| Wound: Do you see long, splintered gashes? | Cicadas. (Harmless on mature trees.) | Borers (Holes), Girdlers (Clean Cut), Cankers (Sunken Bark). |
| Frass: Do you see sawdust on the bark or at the base of the tree? | Borers. (High Alert!) | Cicadas, Twig Girdlers. |
| Timing: Is it a known periodical cicada emergence year in your specific area? | Could be a factor. | Twig Girdlers, Borers, Disease (these are year-round threats). |
| Trunk: Is there scarring or missing bark near the base of the tree? | Mechanical Damage (“Lawnmower Blight”). | Cicadas. |
Frequently Asked Questions
Do trees recover from cicada damage?
Yes, in most cases. Healthy, mature trees typically recover from cicada damage without any long-term issues. The “flagging” is essentially a natural pruning. However, young trees (planted within the last few years) and older, stressed trees are more vulnerable and may suffer stunted growth.
Do I need to protect my trees from cicadas?
For large, healthy trees, protection is generally not necessary. However, you should consider protecting young trees and small ornamental or fruit trees. The most effective method is to cover them with fine mesh netting (with holes no larger than 1/4 inch) before the cicadas emerge.
What’s the difference between cicada damage and squirrel damage?
Cicada damage is very specific: long, splintered, surgical-like slits on small, 1/4 to 1/2 inch diameter twigs in the outer canopy. Squirrels, conversely, may chew on bark to build nests or feed, which results in torn, shredded patches that are often much larger, irregular, and may be on the main trunk or larger branches. Squirrels can also snip off twigs, but often leave a clean, angled cut unlike the messy slits left by cicadas.
Conclusion: A Vigilant Eye Protects Your Trees
While cicadas are a fascinating and generally harmless part of our ecosystem, the real danger they pose is the false sense of security they can create. By automatically attributing all tree damage to them, you risk overlooking far more serious threats like the Emerald Ash Borer or aggressive fungal diseases.
Take a few extra moments to be a “tree detective.” A closer look can reveal the true culprit behind the damage. By learning to distinguish the temporary marks of cicadas from the warning signs of more persistent problems, you can take the right steps to ensure the health and longevity of your valuable trees.
