What’s Causing Dead Patches in Your Tree Canopy?

Have you ever looked up and noticed the canopy of your trees (the upper part of the tree with foliage) is looking a little bare? Maybe there are a few dead branches or areas without many leaves. We often hear from our customers as they worry about dead patches in the tree canopy and wonder what happened to their once beautiful trees.

Here are many reasons why your trees may have dead patches in the canopy. In this article, we’ll look at some common causes of canopy dieback and what you should do when you notice leaf loss and patchiness in your trees.

Key Takeaways

• You should speak with an arborist if you notice dead areas in the canopy of your trees.
• Pests and diseases pose threats to your trees that can lead to dead branches and leaf loss.
• Environmental factors such as drought, excessive heat or cold, and rapidly changing temperatures may also impact the tree canopy.
• To protect your tree, avoid damaging the roots, compacting the soil, or over-fertilizing the tree.
• You should act fast to prevent further damage to your tree and minimize the stress a limited canopy poses.

What to Do When You Notice Dead Patches in the Tree Canopy

A patchy canopy is often a sign of stress to your tree. If you cannot detect the reason yourself, having an ISA Certified Arborist perform an arborist assessment will help diagnose any problems with your trees and find an effective solution to improve your tree’s health.

Many common causes of a tree with a patchy or dying canopy are reversible if you begin treatment in time. Fast action can save your tree and prevent additional damage while waiting may leave the problem unchecked and your tree unhealthier.

What is causing dead patches in my tree’s canopy?

Canopy damage can be caused by factors both visible and hidden. You may have trouble with your trees from external factors like pests and weather, or internal issues like root problems or invisible diseases.

PRO TIP: The Virginia Department of Forestry has created a handbook to help residents identify the different types of issues trees face in our state.

Emerald ash borer adult, in tunnel photo by Eric R. Day, Virginia Polytechnic Institute and State University, Bugwood.org

1. Insects and Other Pests May Be Attacking Your Tree

In northern Virginia, we face a host of bugs and animal pests that can damage your trees. Pest damage can vary from minor aesthetic damage to life-threatening injury.

Some of the common pests of northern Virginia that attack tree canopies include:

• Balsam Woolly Adelgid (Adelges piceae): These pests attack fir trees like balsams (Abies balsamea) and Fraser firs (Abies fraseri). The adults attack a tree by injecting saliva into the tree and disrupting water movement. The canopy will end up thinning, you’ll notice dead patches of needles, and the tree will die within a few years. These pests are an invasive species from Central Europe.
• Emerald Ash Borer (Agrilus planipennis): The emerald ash borer (EAB) attacks ash trees. The larvae grow within the tree and feed on the inner bark. The typical sign of EAB infestation is woodpeckers stripping the bark off a tree to get to the larvae inside. If you don’t have a professional treat the infestation, you will notice a thinning canopy and the death of the tree if left uncontrolled for a few years.
• Spongy Moth (Lymantria dispar): Spongy moths (formerly called gypsy moths) are an invasive species that can rapidly damage your tree’s canopy. The caterpillars feed on leaves, quickly defoliating a tree if there are great enough numbers. Typical trees the spongy moth attacks include oak, hickory, beech, birch, willow, and spruce. The government of Fairfax County urges residents to contact them about any sightings of spongy moth caterpillars.

2. Tree Diseases Can Cause Rapid Canopy Dieback if Left Untreated

Many tree diseases cause thinning of the tree canopy. A tree may lose leaves in response to the stress the disease causes, or the disease may prevent the tree from being able to produce new buds. Some of the common diseases in northern Virginia that affect trees include:

• Littleleaf Disease: Littleleaf disease is a root rot that affects pine trees. You may notice shortened needles and dead patches in the canopy of the tree with a yellow color. You can attempt to prevent littleleaf disease by keeping your soil well-drained or purchasing cultivars with resistance to the disease. You should also contact a professional to remove your infected tree before the disease spreads.
• Beech Bark Disease: Beech bark disease targets American beech (Fagus grandifolia). You might notice this fungal disease due to your tree developing cankers and dying leaves. Insects, wind, and water splashing may spread the disease, and we typically notice infections in the fall.
• Rhizosphaera Needle Cast: This disease attacks many conifers, with the Colorado blue spruce (Picea pungens) as the most susceptible. Rhizosphaera needle cast will attack the lower needles first and move up the tree, eventually causing a patchy and thin canopy. This disease typically damages the look of a tree, rather than leading to a dead tree.
• Beech Leaf Disease: Another disease that attacks the American beech, beech leaf disease will reduce the canopy and may kill a sapling in a few years. Our understanding of beech leaf disease is still developing, and we believe nematodes are responsible for the rapid transmission of the disease. This disease first appeared in Virginia in 2021.
• Anthracnose: Anthracnose typically is not life-threatening to a tree but can be quite unsightly. The pathogen first causes damage to leaves in the lower canopy, with the damage progressing up the tree over time. The best way to help your tree deal with anthracnose is to keep it healthy and free of stress throughout the year, as healthy trees can typically shrug off the disease.
• Oak Decline: Oak decline is not a singular disease, but a combination of factors that damages and weakens oak trees across northern Virginia. During oak decline, you may notice dead patches of leaves, sprouts on the trunk, and a thin canopy. Oak decline affects older trees; they are more vulnerable to stressors and environmental factors.

PRO TIP: Determining the exact cause of problems with your trees is difficult for a layperson. Our team at Absolute Tree can send an ISA Certified Arborist to identify the problem and provide you with actionable solutions to get your trees back to full health.

3. Girdling Roots Can Cause Patches in the Canopy

A tree usually develops girdling roots as a result of poor planting, such as planting too deep, too shallow, or in a confined area. We also sometimes see girdling roots in trees grown in pots.

Girdling roots are roots that encircle the trunk of the tree, constricting the base, and cutting off the tree’s access to moisture and nutrients in the soil. This will result in dead leaves, a thin canopy, and branch dieback over time.

If you cannot see the tree’s root flare (area at the base of the tree where the trunk begins to widen) or you notice shallow roots, there’s a good chance your tree has girdling roots.

If you have a tree experiencing girdling roots, you may be able to remove the circling roots by excavating around the tree’s base. Larger roots may require multiple removal sessions, as removing too many roots at once can cause shock in a tree and lead to death.

WARNING: Removing too many roots at once can kill your tree. Speak with a Certified Arborist who can handle any potential root removal to avoid causing long-term damage to the tree.

4. Root Damages Can Lead to Canopy Thinning

Trees use their roots to absorb necessary nutrients and moisture from the soil, as well as for stabilization. Damaged or cut roots cannot perform these functions, leaving the tree stressed and possibly at risk of falling over. You’ll notice wilting and dying leaves in the tree canopy, with the damage progressing over time until the tree becomes defoliated.

Tree roots are susceptible to damage from landscaping work, such as trenching for utility or irrigation lines, installing a swimming pool, or doing grading work. Nearby construction, such as a home extension or building retaining wall, as well as paving over the tree’s root zone or driving heavy vehicles over it can all damage or sever tree roots.

To prevent these types of root damage, consult with an arborist if you plan to do any construction or major landscaping workg near a tree. A certified arborist can develop a tree protection plan that will help you determine where it is safe to build and how to minimize irreversible damage to your trees.

5. Cold Injuries Can Leave Trees with Poor-Looking Canopies

While our winters in Fairfax and Arlington counties are often not terribly cold, we sometimes see unseasonably warm or cold conditions over the winter months. These extreme temperatures or rapid temperature fluctuations can cause cold injuries such as sunscald or frost cracks in trees.

If trees suffer from cold injuries, they will often have difficulty developing new growth in the spring and summer. This can lead to a tree with dead branches and sparse foliage.

Prevention of cold injuries is mostly down to making proper choices when you plant trees. Choose trees that work within the hardiness zone you live in. For Fairfax County residents, most of us live within Zone 7a, with coastal residents being in Zone 7b.

The same is true for Arlington County, with most residents in Zone 7a and a few residing within 7b.

If you notice your trees have suffered cold injuries, be careful about pruning your trees. Don’t prune until you know the extent of the damage, and consider hiring a professional pruning service to avoid further damaging your tree.

6. Soil Compaction Leaves a Tree Unable to Get the Nutrients It Needs

Soil compaction occurs whenever enough foot traffic takes place under a tree or when a vehicle drives over the soil where a tree’s roots are.

Compacted soil has less space for air and water to collect in the ground. You may notice water-saturated soil and an unhealthy tree. Trees in compacted soil have poorer root health and less root growth. These unhealthy trees will likely begin to lose leaves, leading to patchy canopies and poor aesthetic appearance.

To avoid soil compaction in heavily trafficked areas, consider placing a barrier around the tree to exclude people and vehicles from the root zone areas. Laying organic mulch around the tree out to the drip line will also discourage foot traffic and has the added benefit of increasing tree health.

This diagram demonstrates the proper way to water a tree. You should aim to water at the edge of the canopy, rather than directly at the base.

7. Drought Can Leave a Tree with a Spotty Canopy

In Fairfax and Arlington Counties, we typically get enough rainfall in the summer to avoid extreme cases of drought. However, most years we see conditions the government describes as “abnormally dry.”

For example, in June 2023, over ¾ of Fairfax County spent most of June in a state of “moderate drought,” while approximately ⅓ of residents even experienced “severe drought” at some point. These were some of the worst drought conditions in the county since 2018.

Likewise, for Arlington County, residents across the county were in the “moderate drought” classification in June 2023.

Anytime there is a drought warning in your area, monitor your trees carefully for signs of stress and damage.

Drought can lead to leaf scorch, wilting, leaf shedding, and defoliation. It will also leave a tree stressed and more susceptible to pests and diseases.

In drought conditions, increase irrigation to your trees. Ensure you water around the edge of the canopy, rather than at the tree base where there are no roots. Most of the roots extend to the edge of the canopy, and by watering there, you will get your tree the water it needs during a drought.

Newly planted trees need more water and attention than older trees until they are fully established. To ensure you are getting them enough water, check with an arborist to plan a watering schedule and consideror setting up drip irrigation to keep your trees healthy throughout the summer.

8. Over- and Under-Fertilization Can Lead to Dead Leaves and Unhealthy Trees

Proper fertilization is vital for trees and helps them grow properly. Over-fertilization, however, can have negative effects on your tree, including dead patches in the canopy.

Over-fertilizing can burn tree roots, while under-fertilization will leave the tree starved of necessary nutrients. In both cases, you’ll see smaller leaves, premature leaf drop, and reduced twig and branch growth.

Consult an arborist before applying fertilizer to ensure you use an appropriate amount and the correct combination of macro- and micronutrients. An arborist will likely perform a soil test and then recommend a customized tree nutrition plan to keep your trees and shrubs healthy and thriving.

9. Too Much Sun Can Cause Leaf Scorch

Trees need sunlight to survive, but too much sunlight can have negative effects. Over-exposure to the sun can cause leaf scorch, where the leaves dry up, turn brown, and may fall off. These problems are often exacerbated by other factors, like root damage or lack of water.

Leaf scorch is often an issue for younger trees, as well as some trees with lacy leaves such as some varieties of Japanese maple. You’ll need to monitor your plants carefully in the summer when UV radiation is at its peak.

If you notice leaf scorch on a young tree, we recommend replanting it in a place on your property that receives less sunlight.

Issues for Trees with Dead or Patchy Canopies

The canopy is where a tree performs photosynthesis. More leaves performing the task leads to a healthier tree that will grow faster and larger. When your tree experiences canopy dieback, there will be fewer leaves giving the tree the energy it needs to survive.

While there is nothing wrong with selective pruning of the crown to keep your tree structurally sound and looking good, patchy canopies with dead spots from disease or any other issue need immediate treatment to avoid the problem getting worse.

PRO TIP: A healthy and unstressed tree is better able to deal with the problems it faces than a stressed and unhealthy one.

Call Absolute Tree For a Lush, Green Tree Canopy

Dead patches in the tree canopy are not normal but it’s a common sight in northern Virginia. Given the wide range of possible causes, diagnosing the problem is often difficult without proper training. That’s where the services of an ISA Certified Arborist can make the difference between a tree with a healthy, full canopy and one that ruins the look of your landscape.

If you’re noticing dead patches, leaf loss, or thinning in the canopy of your trees, the team at Absolute Tree Service can help. We can determine what is wrong with your tree and begin a plan to restore it to full health.

Call us at 703-969-6207 or request an estimate online to schedule a consultation and keep your trees lush and green.