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Signs Your Tree May Have a Fungal Infection

Prees trees
November 14, 2025

A thriving tree adds beauty, shade, and value to any property. But when a tree develops a fungal infection, its health can decline quickly and quietly. Fungi attack bark, roots, and leaves, often spreading unseen until the damage becomes severe.

In Tennessee’s warm and humid climate, fungal diseases are especially common. Recognizing the early signs of infection can make the difference between saving your tree and losing it entirely.

In this guide, we’ll cover the most common signs of fungal infection, explain how to identify specific types, and outline the steps homeowners can take to protect their landscape.

For professional help diagnosing or treating sick trees, visit Prees Trees – Tree & Debris Removal.

Why fungal infections are common in Tennessee

Tennessee’s weather patterns provide ideal conditions for fungal growth. Warm temperatures and high humidity create the perfect breeding ground for spores that settle on tree bark and leaves.

Contributing factors include:

  • Frequent rain and poor drainage
  • Dense canopies that trap moisture
  • Improper pruning or storm damage
  • Soil compaction and limited airflow
  • Overwatering or over-fertilizing

Even healthy trees can become infected after a season of heavy rain or strong storms. That’s why preventive care, such as proper pruning and drainage management, is essential. Learn more about proactive maintenance in How to Prepare Your Trees for Storm Season in Tennessee.

1. Discolored or spotted leaves

One of the earliest indicators of fungal infection is unusual leaf discoloration. If you notice yellow, brown, black, or white spots spreading across leaves, your tree may be battling fungi such as anthracnose, leaf spot, or powdery mildew.

Common symptoms:

  • Yellow or brown spots forming between leaf veins
  • Black or dark lesions that enlarge over time
  • Powdery white or gray coating on leaves (a sign of mildew)
  • Leaves curling, withering, or falling prematurely

What to do:

  • Remove and dispose of affected leaves immediately to prevent spread.
  • Improve airflow by trimming crowded branches.
  • Avoid watering leaves directly—water at the soil level instead.

Consistent pruning and cleanup can greatly reduce fungal spores in your yard. You can find trimming guidance in Tree Pruning Techniques Every Homeowner Should Know.

2. Mushrooms or fungal growth on the trunk or base

Mushrooms growing at the base of a tree or along the trunk are a strong sign of internal decay. These fruiting bodies indicate that fungi have invaded the tree’s heartwood, breaking down structural tissue from the inside out.

Warning signs:

  • Clusters of mushrooms near the roots
  • Fungal conks or brackets emerging from the bark
  • Soft or spongy areas around the base
  • Hollow-sounding wood when tapped

Common causes:

  • Root rot (caused by Armillaria or Phytophthora fungi)
  • Heart rot in mature hardwoods
  • Excess moisture or compacted soil

What to do:

If mushrooms appear repeatedly, have a certified arborist inspect the tree immediately. Root and trunk rot often mean structural instability, which can make trees hazardous during storms. In severe cases, you may need professional Emergency Tree Removal for safety.

3. Cracked or peeling bark

Healthy bark protects a tree from disease and pests. When fungal infection takes hold, it disrupts this defense layer, causing bark to split, peel, or flake away.

Symptoms to look for:

  • Vertical cracks running up the trunk
  • Sunken cankers with dark, oozing sap
  • Patches of missing bark revealing discolored wood underneath
  • Rapid bark shedding after heavy rain

Canker-causing fungi such as Cytospora or Nectria are especially common in stressed trees. They enter through wounds caused by improper pruning or storm injury.

Prevention tips:

  • Avoid damaging bark with lawn equipment.
  • Prune properly to create clean cuts that heal quickly.
  • Keep mulch 2–3 inches away from the trunk to reduce moisture buildup.

4. Wilting leaves despite adequate watering

When leaves wilt or droop even though soil moisture is sufficient, it can indicate a vascular fungal infection such as Verticillium wilt or Fusarium wilt. These pathogens clog a tree’s internal water transport system, starving leaves and branches.

Key identifiers:

  • Wilted leaves that do not recover after watering
  • Brown streaks visible in the sapwood beneath the bark
  • Uneven leaf death, often starting on one side of the tree
  • Premature leaf drop during growing season

Unfortunately, these infections are often irreversible once established. However, early pruning and soil treatments can slow the spread and give the tree a chance to recover.

5. Dieback in branches and twigs

Gradual dieback, where branches lose leaves and fail to produce new growth, is another hallmark of fungal disease. Infected tissue cuts off nutrient flow, slowly starving parts of the canopy.

Signs of dieback:

  • Sparse foliage concentrated on outer branches
  • Twigs snapping easily with dry, brittle interiors
  • Dead tips progressing inward each season
  • No new buds forming during spring

This symptom is often linked to canker diseases, root rot, or Dutch elm disease. Once dieback reaches the main trunk, removal is typically the safest option to prevent collapse.

6. Abnormal growths or swellings

Fungal infections sometimes cause trees to develop strange lumps or swellings on trunks or branches known as galls. These are abnormal growth responses to infection.

How to recognize them:

  • Round, irregular knots on branches
  • Woody bulges near pruning wounds or damaged bark
  • Cracked or deformed bark surrounding growths

While some galls are harmless, others signal severe infection and stress. Removing affected limbs and disinfecting tools between cuts helps prevent further spread.

7. Foul odor or oozing sap

Fungal infections that progress into decay often release a sour or musty odor. You may also notice sticky sap leaking from wounds or cracks, a sign that the tree is fighting internal infection.

Warning indicators:

  • Dark, oozing sap resembling tar or honey
  • Strong, unpleasant smell near the trunk base
  • Insect activity around leaking areas (beetles, ants, wasps)

This symptom is often seen in slime flux or wetwood, both of which result from bacterial or fungal invasions. A professional diagnosis is important since improper cleanup can worsen the condition.

8. Premature leaf or needle drop

If your tree is shedding leaves or needles long before fall, a fungal disease could be to blame. Species like pines, oaks, and maples are especially prone to this issue.

Typical culprits:

  • Needle cast disease (common in conifers)
  • Anthracnose (common in hardwoods)

Signs to watch for:

  • Uniform yellowing before drop
  • Bare branches at the lower canopy first
  • Black or brown spots on fallen leaves

Early intervention with fungicidal sprays or professional pruning can prevent repeat infections the following year.

9. Visible mold or mildew on surfaces

Powdery mildew and sooty mold are surface fungal infections that are easy to recognize. While often cosmetic at first, they can weaken trees if left untreated.

Symptoms:

  • White, powdery film covering leaves or twigs
  • Black, sticky mold on leaves (usually from honeydew secreted by insects)
  • Reduced sunlight penetration to lower branches

Control methods:

  • Improve air circulation with careful thinning.
  • Treat with horticultural oil or neem oil.
  • Control insect populations like aphids or scales that attract mold.

Surface molds are usually treatable with consistent care and cleaning.

10. Slow overall growth

When fungal infections affect roots or internal vascular systems, trees may exhibit slower growth and reduced vigor. You might notice smaller leaves, shorter branches, and thin canopies.

Contributing factors:

  • Root rot limiting nutrient uptake
  • Soil-borne fungal pathogens such as Armillaria
  • Chronic stress from poor drainage or overcrowding

Improving soil aeration and applying organic mulch can help strengthen a recovering tree, but severely infected roots often require professional removal for safety.

How to confirm a fungal infection

Because symptoms often resemble other issues like drought or insect infestation, professional diagnosis is key. Certified arborists can take tissue samples or perform soil tests to identify specific pathogens.

They may recommend:

  • Targeted fungicide treatments
  • Soil aeration and nutrient management
  • Structural pruning to improve airflow
  • Complete removal of infected trees if necessary

Once a fungal issue is confirmed, fast treatment is crucial to prevent it from spreading to nearby trees.

Preventing fungal infections before they start

Prevention is always more effective than treatment. Healthy trees have natural defenses against disease, and simple maintenance habits go a long way in keeping them strong.

Best practices for prevention:

  • Prune regularly to improve airflow and remove dead limbs.
  • Avoid overwatering and ensure proper drainage.
  • Mulch properly but keep mulch away from the trunk.
  • Disinfect tools between pruning cuts.
  • Remove fallen leaves and debris that harbor fungal spores.

A clean, well-maintained yard creates an environment where fungi struggle to take hold. For full cleanup and hauling, contact Prees Trees – Tree & Debris Removal.

Frequently asked questions

Q: Can a tree recover from a fungal infection on its own?
Mild infections can sometimes resolve naturally, but most require pruning or fungicide treatment to prevent worsening.

Q: Should I fertilize a tree that has fungus?
Fertilizing stressed or infected trees can sometimes accelerate fungal growth. Always consult an arborist before applying fertilizers.

Q: Is it safe to keep an infected tree near my home?
If the infection affects structural integrity, the tree may become hazardous. An arborist can determine if removal is necessary.

Conclusion: Early detection is key to saving your trees

Fungal infections can destroy trees from the inside out, often with little warning. Recognizing early signs such as discoloration, wilting, or fungal growth allows you to act quickly and protect your landscape.

Key takeaways:

  • Look for mushrooms, oozing sap, or unusual leaf discoloration.
  • Improve airflow and drainage to prevent fungal spread.
  • Schedule professional inspections for suspected infections.
  • Remove severely infected or unstable trees for safety.

For reliable inspection, treatment, and cleanup across East Tennessee, contact Prees Trees – Tree & Debris Removal. Their experts can diagnose fungal infections, provide safe removal, and restore your property’s natural beauty before storm season strikes.

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