Tree Diseases

Signs, causes, and cures to keep your trees thriving

Tree Diseases Guide

Tree diseases can turn a thriving landscape into a vulnerable one if left untreated. Early identification, knowledge of the causes, and the right treatment plan are key to protecting your trees. At Niwaki Tree and Shrub, we help homeowners, property managers, and tree lovers take control of tree health through education and expert support.

What Causes Tree Diseases?

Tree diseases are most commonly caused by fungi, bacteria, or viruses, often made worse by environmental stress. Poor drainage, improper pruning, compacted soil, and weather extremes can weaken a tree’s defenses, leaving it vulnerable to infection. Some diseases are spread by insects, others by airborne spores or contaminated tools.

Common Tree Diseases in South Carolina

Anthracnose – A fungal disease that causes brown spots and premature leaf drop, especially in dogwoods, oaks, and sycamores.
Powdery Mildew – Appears as a white, powder-like coating on leaves. Common on maples, crepe myrtles, and fruit trees.
Root Rot (Phytophthora) – Caused by poor drainage or overwatering, this disease damages roots and leads to yellowing and dieback.
Fire Blight – A bacterial disease affecting apple, pear, and crabapple trees. Leaves appear scorched and branches wilt.
Canker Diseases – Sunken, discolored lesions on branches or trunks that may ooze sap. Often caused by fungal pathogens.
Sooty Mold – Grows on the honeydew secreted by aphids or scale insects, covering leaves in black residue that blocks sunlight.

How Tree Diseases Spread

Tree diseases can spread in several ways — through water, wind, soil, insects, animals, and even human activity. Fungal spores can travel on the wind or splash onto leaves during rain. Insects may carry pathogens from one tree to another as they feed. Tools that aren’t properly sanitized can transfer bacteria or fungal material. Once a tree is weakened by drought, injury, or poor soil, it becomes even more vulnerable to infection. Understanding how diseases spread helps homeowners and professionals break the cycle and stop pathogens before they take hold.

Signs and Symptoms of Tree Diseases

How to Identify Tree Diseases

Look for leaf discoloration, spots, or curling
Check for dead or dying branches
Observe bark for cankers, cracks, or oozing sap
Inspect root zone for mushrooms, soft wood, or poor growth
Monitor seasonal changes in leaf production or color
Take photos and note when symptoms first appeared to assist with professional diagnosis.

What are the early warning signs of tree disease?

Subtle symptoms like slight leaf discoloration, minor wilting, or slower growth can be early red flags. Trees may still appear healthy from a distance, but close inspection can reveal hidden issues.

How to tell the difference between pest damage and disease

Pest damage often includes visible insects, chewed leaves, or bore holes. Diseases tend to present with discoloration, spots, or fungal growth. However, the two can overlap — pests often spread disease.

How to check leaves, bark, roots, and branches for infection

Inspect leaves for unusual spots, mildew, or curling. Look at bark for cankers, cracks, or oozing sap. Check roots for mushrooms or soft, decaying wood. On branches, note any dieback, wilt, or unseasonal shedding.

How To Prevent Tree Diseases

🌿 Prune Properly: Remove infected limbs during dry weather and sanitize tools between cuts.

🌿 Improve Drainage: Avoid overwatering and compacted soil to support strong root systems.

🌿 Apply Fungicides and Bactericides: Use treatments when necessary, and only according to label directions.

🌿 Boost Tree Health: Mulch correctly, avoid injuries to the bark, and maintain soil quality.

🌿 Monitor and Maintain: Schedule regular tree check-ups and act on early signs of stress or disease.

Tree Disease Treatment & Recovery

Not every tree disease spells disaster — many can be treated successfully with the right combination of care, timing, and patience. Once a disease is identified, taking quick action improves the chances of recovery.

Early Intervention: Begin treatment as soon as symptoms appear. Remove affected branches and apply appropriate fungicides or bactericides to stop spread.
Supportive Care: Strengthen the tree’s natural defenses through watering during dry spells, enriching the soil with compost, and applying mulch to regulate moisture.
Monitor Progress: Observe the tree through each season and document changes. Look for signs of new growth, healthy leaves, and reduced symptoms.
Rehabilitation Pruning: In cases of moderate dieback, targeted pruning over several seasons can encourage a healthier branch structure.
When to Remove: If disease reaches the trunk, compromises over 50% of the canopy, or leads to major decay, removal may be the safest option. Replanting with a resistant species is often recommended.

Seasonal Tree Diseases And Prevention Guide

Spring

Warm, wet weather triggers fungal growth. Watch for leaf spot, anthracnose, and powdery mildew. Apply preventive fungicides if needed and ensure proper airflow through pruning.

Summer

High heat and humidity can lead to stress and increased pest activity. Sooty mold and bacterial infections may become more visible. Water deeply, monitor for early symptoms, and avoid overhead irrigation.

Fall

As leaves drop, it’s easier to spot structural damage and lingering fungal issues. Clean up debris to prevent disease carryover and apply mulch to insulate roots.

Winter

Dormant trees are less active but still vulnerable. Prune diseased or damaged limbs and plan ahead for spring treatments. Avoid wounding bark and inspect for cankers or decay.

Need help diagnosing a tree disease? Contact our tree experts

Contact Information

Office: 3317 Williamson Rd., Rock Hill, SC 29730

Phone: 803-366-3296, 704-980-9516

Email: niwaki.tree@gmail.com

We are open: Monday – Saturday 7 AM – 7 PM