Tree Health — MA & NH

Common Tree Diseases & Pests in Massachusetts & New Hampshire

From the emerald ash borer to winter moth and beech leaf disease, New England's trees face real threats. Here's how to spot the warning signs early — while your tree can still be saved.

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How to Tell If Your Tree Is Sick

A tree rarely fails overnight. Most diseases and infestations announce themselves months or even years in advance — if you know what to look for. Catching the signs early is the difference between a treatable problem and a removal.

✓Canopy dieback — dead branches starting at the top or outer tips and working inward, or a canopy that's noticeably thinner than neighboring trees.
✓Discolored or early-dropping leaves — yellowing, browning, spotting, or fall color arriving weeks ahead of schedule.
✓Bark changes & cankers — cracks, oozing sap, sunken dead patches, or peeling bark.
✓Fungal growth — mushrooms or shelf fungi at the base or on the trunk, a classic sign of internal decay.
✓Boreholes & sawdust — small exit holes, tunneling under the bark, or fine sawdust ("frass") at the base — telltale insect activity.
✓Defoliation — leaves chewed away in late spring or early summer, often a caterpillar or moth infestation.

The Insect Pests Threatening MA & NH Trees

A handful of invasive and native insects do the most damage across Massachusetts and New Hampshire:

Emerald Ash Borer

A metallic-green beetle whose larvae tunnel beneath the bark and cut off an ash tree's ability to move water. It's now established across the region and is nearly always fatal to untreated ash. Watch for canopy thinning, D-shaped exit holes, and woodpecker activity.

Winter Moth

Especially common in eastern and coastal Massachusetts, winter moth caterpillars defoliate oaks, maples, and fruit trees in spring. Repeated years of defoliation weaken and eventually kill otherwise healthy trees.

Spongy Moth (formerly Gypsy Moth)

Periodic outbreaks strip whole stands of oak and other hardwoods bare in early summer. A single season rarely kills a healthy tree, but back-to-back years — especially combined with drought — can.

Asian Longhorned Beetle

A serious threat to maples and other hardwoods, tied to an active quarantine in central Massachusetts. Look for round exit holes about the width of a pencil and shallow oval scars where eggs were laid.

Hemlock Woolly Adelgid

Tiny insects that coat the undersides of hemlock needles in white, cottony masses, slowly starving the tree. Widespread on hemlocks throughout the region.

Not Sure What You're Seeing?

Correct identification drives the right response. A certified arborist can diagnose the pest, judge how far it's progressed, and tell you whether treatment or removal is the smarter call.

Common Tree Diseases in New England

Fungal and bacterial diseases are just as damaging as insects, and several are widespread here:

✓Dutch elm disease — a fungus spread by bark beetles that has devastated American elms; rapid wilting and yellowing of the crown is the classic sign.
✓Beech leaf disease — an emerging threat across New England, showing as dark banding between leaf veins and thinning canopies in beech trees.
✓Anthracnose — a fungal disease of oaks, maples, sycamores, and dogwoods causing leaf spots, curling, and early leaf drop in cool, wet springs.
✓Apple scab & cedar-apple rust — common on crabapples and ornamentals, causing spotting, distortion, and premature defoliation.
✓Needle cast & blights — fungal diseases of spruces, pines, and other evergreens that brown and drop needles from the inside out.
✓Root & butt rot — decay fungi that hollow the base and roots, often signaled by fungal brackets and a growing risk of failure.

A diseased tree near a home, driveway, or walkway can become a structural hazard. If you're worried about failure risk, a tree hazard assessment is the place to start.

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Quick Tree-Health Questions

Can a sick tree be saved?

Often yes — if it's caught early. Many pests and diseases are treatable in their early stages through targeted care. Once decay or infestation is advanced, removal may be the safer choice. An arborist assessment tells you which.

How do I know if it's a pest or a disease?

Chewed or defoliated leaves, boreholes, and sawdust point to insects; leaf spots, cankers, wilting, and fungal growth point to disease. They can also occur together. Correct ID is what determines the right response.

Is a diseased tree dangerous?

It can be. Internal decay and root rot weaken a tree's structure, raising the risk of limb or whole-tree failure — especially near homes and walkways. A hazard assessment gauges the risk.

When should I call an arborist?

As soon as you notice dieback, unusual leaf drop, boreholes, or fungal growth. Early diagnosis gives you the most options and the best chance of saving the tree.

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What to Do About a Diseased or Infested Tree

The right move depends entirely on the problem and how far it's progressed — which is why diagnosis comes first. In many cases, early-stage pests and diseases can be managed and the tree kept healthy. In others, the damage is too advanced and removal is the safest option to protect people, property, and the healthy trees nearby.

✓Get an accurate diagnosis first — a certified arborist identifies the pest or disease and how far it's spread before anything is done.
✓Act early when the tree can be saved — timely pruning of affected limbs and proper care can stop many problems from spreading.
✓Remove when it becomes a hazard — a tree with advanced decay, root rot, or a fatal infestation near your home should be assessed for removal.
✓Protect the trees nearby — some diseases and pests spread; prompt action helps safeguard the rest of your landscape.

Worried about a specific tree? Request a free estimate and we'll take a look.

Is Your Tree Sick? Warning Signs at a Glance

Is your tree sick — warning signs of tree disease and pests in Massachusetts and New Hampshire: canopy dieback, discolored leaves, cankers, fungal growth, boreholes, and defoliation — AA Tree Service provides tree health assessments across Massachusetts & New Hampshire. Free estimates available.

Related Tree-Health Services & Guides

Explore related services across MA & NH:

Tree Hazard Assessment Tree Risk Assessment Signs a Tree Is Dying Warning Signs You Need Removal Routine Tree Maintenance Certified Arborist

Tree Diseases & Pests — Frequently Asked Questions

What are the most common tree pests in Massachusetts and New Hampshire?

The most damaging include the emerald ash borer (ash trees), winter moth (oaks, maples, and fruit trees, especially in eastern MA), spongy moth (oaks and hardwoods), Asian longhorned beetle (maples, tied to a central-MA quarantine), and hemlock woolly adelgid (hemlocks). Each has distinct signs, so accurate identification matters before deciding on treatment or removal.

How can I tell if my tree is dying versus just stressed?

Temporary stress — from drought or a rough season — usually shows up as wilting or early leaf drop that the tree recovers from the following year. Signs of a dying tree are more persistent and progressive: worsening canopy dieback, large dead limbs, fungal brackets at the base, bark falling away, and no new growth. When the decline continues season over season, it's time for a professional assessment.

Can a diseased or infested tree be saved?

Frequently, yes — if the problem is caught early. Many pests and diseases can be managed in their early stages through targeted pruning and proper care, allowing the tree to recover. Once decay, root rot, or a fatal infestation is well advanced, removal becomes the safer option. Early diagnosis is what preserves your choices.

Is a diseased tree a safety hazard?

It can be. Internal decay, root rot, and dead limbs weaken a tree's structure and raise the risk of failure — a special concern when the tree overhangs a house, driveway, or walkway. If you're unsure, a tree hazard assessment evaluates how likely the tree is to fail and what to do about it.

Will one tree's disease spread to my other trees?

Some can. Certain diseases and pests move from tree to tree — through the soil, root grafts, bark beetles, or simply by the insects flying to the next host. That's why prompt diagnosis and action matter: addressing an affected tree early helps protect the rest of your landscape.