Why Do Trees Die? Common Causes

People call me all the time and say, "Keith, I have no idea what happened — the tree just died." But trees do not just die out of nowhere. Something killed it. You just did not see it happening. After 30 years of removing dead and dying trees across Middlesex County, I have seen the same causes come up over and over again. Here is what actually kills trees in Massachusetts — and how to catch it before it is too late.

Can Trees Die of Old Age?

Technically, yes. Trees do have lifespans. A white birch might live 80 years. A red oak can push 300 years or more. Sugar maples, 200 to 400 years. But here is the thing — in a residential setting, almost no tree dies purely of old age. Something else gets it first: disease, insects, storm damage, construction, or drought. Old age weakens a tree's defenses, and then one of these other factors delivers the final blow.

That massive oak in your backyard in Chelmsford that has been there since your grandparents' time? It is not dying of old age. It is dying because its root zone has been compacted by 40 years of foot traffic and lawnmowers, or because the driveway extension in 2015 severed a major root, or because honey fungus has been quietly eating its way through the heartwood for the past decade. Old age set the stage. Something else pulled the trigger.

Disease: The Silent Killers

Fungal Infections

Fungi are responsible for more tree deaths in Massachusetts than any other single cause. The problem is that by the time you see the symptoms, the damage is often severe. Armillaria root rot (honey fungus) attacks the root system of oaks, maples, and dozens of other species. You might notice mushroom clusters at the base of the tree in fall — those are the fruiting bodies of a fungus that has been digesting the roots for years. We see this constantly in older red oaks across Billerica and Tewksbury.

Heart rot fungi like Ganoderma and Phellinus get inside through wounds — a pruning cut, a broken branch, a lawnmower nick — and slowly hollow out the trunk. The tree looks fine from the outside until it is 70 percent hollow and a windstorm snaps it in half. I have cut down oaks in Andover that looked perfectly healthy until the saw went through and you could see the interior was completely rotted out.

Bacterial Leaf Scorch

This one has been spreading through Massachusetts over the last two decades. It is caused by the bacterium Xylella fastidiosa, which clogs the water-conducting vessels in the tree. Symptoms show up as browning leaf margins in late summer, starting on older leaves and working inward. Red oaks and pin oaks are the most affected species in our area. There is no cure. Affected trees decline over 3 to 8 years and eventually need to come down. We have seen it in nearly every town in our service area.

Insects: The Invaders

Emerald Ash Borer

If you have an ash tree in Massachusetts and it is not being actively treated, it is either dead or dying. The emerald ash borer has devastated ash populations across the entire state. The larvae feed under the bark, cutting off the tree's ability to transport water and nutrients. We have removed hundreds of dead ash trees since the infestation reached Middlesex County. In Billerica alone, I would estimate we have taken down 50 or more dead ash trees in the last five years.

Winter Moth

The winter moth has been hammering oaks across eastern Massachusetts for years. The caterpillars emerge in spring and eat the new leaf buds before they even open. One bad year, a tree can recover. Three or four years of heavy defoliation, and the tree is critically weakened. I have watched it happen in real time across Chelmsford — entire neighborhoods of oaks with thin, struggling canopies because winter moth kept stripping the leaves year after year. The trees do not die from defoliation alone, but weakened trees become easy targets for secondary problems like Armillaria and bark beetles.

Asian Longhorned Beetle

This one is the maple killer. The Asian longhorned beetle was found in Worcester in 2008 and it took a massive federal eradication effort — cutting down over 30,000 trees — to eliminate it. As of 2026, the Worcester quarantine zone has been declared eradicated, but every arborist and tree service in Massachusetts keeps an eye out. If you see a large black beetle with white spots and long antennae on a maple tree, report it immediately. This pest could devastate the sugar maple and red maple populations that define the Massachusetts landscape.

Construction Damage: The Slow Death

This is the one that breaks my heart the most, because it is entirely preventable. A homeowner puts an addition on their house, repaves the driveway, or installs a pool. The excavator drives over the root zone, compacts the soil, and severs major roots. The tree looks fine that year. Maybe it looks a little thin the next year. By year three, the canopy is noticeably declining. By year five, the tree is dead.

Root compaction is a silent killer. Tree roots need oxygen. They grow in the top 12 to 18 inches of soil. When heavy equipment drives over the root zone, it compresses those air spaces and suffocates the roots. The tree cannot tell you it is happening. By the time the canopy shows stress, the root damage is 2 to 3 years old and irreversible.

I see this every year in Westford, Carlisle, and Lexington where homeowners invest in beautiful properties and then accidentally kill their best trees during renovation projects. If you are planning construction near a large tree, fence off the root zone — the critical area extends at least as far as the dripline (the outer edge of the canopy) — and keep all equipment and material storage outside that boundary.

Soil Compaction Without Construction

You do not need an excavator to compact soil. Decades of foot traffic, parking cars on root zones, and heavy riding mowers can gradually compress the soil around tree roots. Trees in public parks, near driveways, and along walkways suffer from this constantly. The symptoms are the same: gradual canopy thinning, smaller leaves, poor color, and eventually major branch dieback.

Road Salt Damage

Every winter, Massachusetts roads get salted heavily. That salt does not just stay on the road. It washes into the soil along roadsides and gets sprayed onto trees by passing traffic. Salt draws moisture out of roots and disrupts nutrient uptake. Trees along heavily salted roads — especially white pines and sugar maples, which are particularly salt-sensitive — often show browning needles or scorched leaf margins on the side facing the road.

In towns with heavy traffic like Lowell, Burlington, and Woburn, road salt damage is a significant contributor to tree decline, especially for trees within 20 feet of the pavement.

Drought Stress

Massachusetts gets decent rainfall on average, but we also get dry spells. The summers of 2020 and 2022 were brutal on trees in our area. Shallow-rooted species like birch, beech, and hemlock are the first to show drought stress — wilting leaves, early leaf drop, branch dieback. A single severe drought usually will not kill a healthy tree, but repeated drought stress weakens it and opens the door for diseases and insects that finish the job.

Poor Planting Practices

A surprising number of tree deaths trace back to how the tree was planted in the first place. Planting too deep (burying the root flare) is the most common mistake. It causes the bark at the base to stay constantly moist, which leads to decay. Circling roots from container-grown trees that were not corrected at planting can girdle the trunk over 10 to 15 years, slowly choking the tree's own vascular system. I have seen 15-year-old maples in Wilmington and Bedford that were dead because nobody straightened the roots when they went in the ground.

What to Do If You Think Your Tree Is Dying

The earlier you catch it, the more options you have. Some problems can be managed with proper care. Others mean the tree needs to come down before it becomes a hazard. Here is what I recommend:

• Check the canopy. If more than 30 percent of the crown is dead, thinning, or showing unusual symptoms, get a professional opinion.
• Look at the trunk. Mushrooms, cankers, deep cracks, and peeling bark are all red flags. See our guide on warning signs a tree needs to come down.
• Check for pests. D-shaped exit holes (ash borer), white fuzzy masses (hemlock woolly adelgid), and leaf damage that repeats every year are signs of infestation. Read our Massachusetts tree pest guide.
• Think about recent construction. If you had work done within 15 feet of the tree in the last 1 to 5 years, that could be the cause.

If a tree is too far gone, the safest thing is to remove it before it drops a limb or falls entirely. Dead trees become brittle fast, and the longer you wait, the more dangerous and expensive the removal becomes. If the tree is threatening your home or power lines, we offer 24/7 emergency service.

Call McDonald Tree Service at (978) 375-2272 for a free assessment. I will come out, look at the tree, and give you an honest answer about whether it can be saved or needs to come down. We serve Billerica, Chelmsford, Tewksbury, Lowell, Wilmington, Burlington, Bedford, Carlisle, Dracut, Westford, Andover, Woburn, and Lexington.