Signs a tree needs an arborist: dead limbs, cracks, decay and pests

Updated · KeystoneProGuide editorial team

Which signs mean a tree needs attention?

Dead wood, cracks, signs of decay, a thinning or dying crown, damage from a storm, and branches growing into the house or the wires. Penn State Extension's Master Gardeners list the occasions to call an arborist: storm damage, dead or hazardous branches, wounds or deep bark cracks, lopsided growth, and before any construction or landscaping that could affect the roots. None of these signs on its own says the tree must come down. They say someone qualified should look at it.

What do dead branches tell you?

That something will fall, sooner or later. Penn State's pruning guide lists dead, dying, decayed or potentially hazardous branches as a reason to prune, along with branches that are cracked or broken. Penn State's advice to shade tree commissions explains how to spot them: an inspection in early spring, before the leaves come out, shows dead and broken branches in the canopy, and a second look in late summer separates branches that are alive and in leaf from those that are not.

The U.S. Forest Service adds that a tree without needles, bark or limbs may have structural defects. Penn State's Master Gardeners note that dead trees are usually more expensive to remove than live ones, because the wood becomes brittle and dangerous.

What are the signs of decay inside a tree?

Some can be seen from the ground. The Forest Service lists conks, broken tops, scars at the base, many fallen limbs, ants and an abundance of woodpecker holes as signs that a tree may have internal rot. Penn State's list for tree inspectors includes deadwood, cracks, decay, cavities, included bark and fungal fruiting structures.

Two cautions from Penn State are worth keeping in mind. A tree can look very healthy, with plenty of green leaves, and still have major structural defects or fungus at its base. And a tree that is diseased is not necessarily a high risk, while a healthy-looking one may have internal decay or root rot. Where a tree's condition is unclear, Penn State's answer is an arborist trained and qualified in tree risk assessment.

Are some trees weaker by nature?

Some structures are. Penn State notes that codominant stems are weakly attached and often break in high winds. Penn State also says species differ in how well they wall off decay, with sugar maple and oak doing better than silver maple and poplar. The International Society of Arboriculture says older and larger trees are more likely to drop branches.

What should you look for after a storm?

Hangers and cracks. Penn State says inspections after major storms, whether summer thunderstorms or winter ice, help find broken branches hung up in live trees that "could fall without warning weeks after a storm." The Forest Service says ice storms can crack large branches that stay on the tree and remain a hazard long after the ice has melted.

Keep away from anything touching a line. Penn State says to avoid power lines even if the power is off, and PECO says not to touch a limb lying on a line and to report it at 1-800-841-4141. For insurance, the Pennsylvania Insurance Department advises taking photos or video of storm damage before any cleanup.

What do pest problems look like?

In Pennsylvania, three insects come up often.

  • Emerald ash borer. Pennsylvania's Department of Conservation and Natural Resources (DCNR) lists upper crown dieback, sprouting along the trunk (epicormic branching), bark splits and flaking, woodpecker damage, D-shaped exit holes and S-shaped tunnels under the bark. It says the insect kills ash trees three to five years after infestation and is found in nearly every county.
  • Hemlock woolly adelgid. DCNR says its egg sacs look like the tips of cotton swabs on the undersides of the newest twigs, and that its feeding causes needle drop, branch dieback and eventually death. It was found in all 67 counties by the end of 2023.
  • Spotted lanternfly. Penn State Extension says heavy feeding has contributed to the death of grapevines, tree-of-heaven and black walnut saplings, but that it is not known to kill other plants directly and is mainly a nuisance in home landscapes. Penn State says the insects' honeydew grows sooty mold that stains trunks, decks and cars beneath a heavily fed-on tree.

The International Society of Arboriculture adds three general symptoms that may call for an arborist: discolored leaves, dead branches and early leaf drop.

What about building work near a tree?

Keep an eye on it afterward. ISA says construction can be deadly to nearby trees, through compacted soil, cut roots, added fill and changes in grade or drainage. The signs of decline it lists are smaller and fewer leaves, dieback in the crown and premature fall color.

Which signs are less serious than they look?

A few. Penn State says lanternflies alone may not kill a tree and that not every tree in an infested area needs treating. Low limbs over a path, branches rubbing the roof or a tree that has simply grown too big are reasons to prune, according to Penn State's list, rather than reasons to remove. Whether you can handle a small job yourself is covered in doing it yourself or hiring a professional.

What should you do next?

If a tree is dead, cracked, leaning on the house or tangled in wires, get a professional opinion soon. If the sign is slower, such as thinning or pests, take time to compare qualified companies: how to choose a tree service sets out the checks. Businesses that serve your area are on the tree services directory page.

Sources

  1. Pruning Landscape Trees, Penn State Extension
  2. Dealing with Tree Risk: Tips for Municipal Shade Tree Commissions, Penn State Extension
  3. When to Call an Arborist, Penn State Extension (Allegheny County Master Gardeners)
  4. Helping Trees Recover After Storms, Penn State Extension
  5. Hazard Trees, U.S. Forest Service
  6. Managing Hazards and Risk, International Society of Arboriculture (TreesAreGood.org)
  7. Tree Health, International Society of Arboriculture (TreesAreGood.org)
  8. Agrilus planipennis (Emerald Ash Borer), Pennsylvania Department of Conservation and Natural Resources
  9. Adelges tsugae (Hemlock Woolly Adelgid), Pennsylvania Department of Conservation and Natural Resources
  10. Spotted Lanternfly Management Guide, Penn State Extension
  11. Our Crews Respond Quickly to Storm Damage, PECO
  12. Natural Disaster Insurance Guide, Pennsylvania Insurance Department

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