Tree fungus refers to organisms that invade a tree’s structure, often entering through wounds or stressed tissue. These fungi consume wood and compromise the vascular system, reducing the tree’s ability to transport water and nutrients. Although not immediately fatal, the decay process weakens the tree over time. Addressing an infection requires a methodical approach, progressing from visual assessment to cultural and chemical treatments. Understanding the specific type of fungal growth and the extent of the damage is the first step toward saving the tree.
Identifying the Type of Fungal Infection
Proper identification is the starting point for any successful treatment plan, as different fungi require different approaches. Surface fungi commonly appear as powdery mildew, presenting as a white or gray dusty coating on leaves and young shoots. Another common sign is leaf spot, which manifests as discolored blotches that are yellow, brown, or black and can cause premature leaf drop.
Infections that penetrate deeper into the tree structure require immediate attention. Cankers are distinct sunken, dead areas on a branch or trunk, sometimes accompanied by sap oozing from the margin of the lesion. The appearance of shelf-like or bracket fungi, also known as conks, on the trunk or near the root flare indicates that the fungus is actively decaying the internal heartwood.
Physical and Cultural Removal Strategies
Non-chemical methods should focus on removing infected material and improving the tree’s overall resilience. Pruning is a primary strategy, requiring the removal of infected branches by cutting back to healthy wood. Cuts should typically be made at least eight to twelve inches beyond any visible symptom. This practice removes the immediate source of the pathogen and prevents its spread to other parts of the tree.
Tool sanitation is essential to avoid transmitting fungal spores from diseased tissue to healthy wood. Pruning shears and saw blades should be sterilized between cuts using a solution of 70% isopropyl alcohol or a diluted bleach mixture. Cultural practices also play a significant role by removing all infected debris, including fallen leaves and pruned branches, from the area around the tree.
Improving the tree’s environment helps the tree resist further infection. Thinning the tree’s canopy enhances air circulation, which reduces the humidity and moisture retention fungi need to thrive on leaf surfaces. Ensuring proper soil drainage and avoiding excessive watering minimizes stress on the root system, promoting robust tree health.
Selecting and Applying Chemical Treatments
When physical removal and cultural strategies are insufficient, chemical treatments can stop the fungal progression. Fungicides are generally categorized into two main types: contact and systemic. Contact fungicides act as a protective barrier on the surface of the plant tissue, preventing fungal spores from germinating and penetrating the plant.
Systemic fungicides are absorbed into the tree’s vascular system and move internally to protect new growth and treat existing infections. They are typically applied as a soil drench around the tree’s base or injected directly into the trunk. Common active ingredients include copper-based compounds, often used as a broad-spectrum preventative, and sulfur-based fungicides, which are effective against surface diseases like powdery mildew.
Timing is crucial for the effectiveness of chemical application. Many treatments require application early in the season, such as in early spring before bud break, to prevent infection before spores become active. Following label instructions is necessary to ensure safety and prevent damage to the tree or surrounding environment. Wear protective equipment and avoid application during high wind or rain, which can cause the chemical to drift.
Assessing Damage and Knowing When to Consult an Arborist
The decision to transition from do-it-yourself treatment to professional intervention rests on assessing the severity of the decay. Advanced decay is often indicated by the presence of large shelf fungi high on the trunk or in major scaffold branches. The appearance of mushrooms or conks at the root collar or base of the trunk is a strong indicator of root rot, which can lead to the failure of the entire tree.
Other warning signs include a sudden lean, deep cracks or splits in the main trunk, or wood that feels soft or spongy when probed. If the tree is located near a house, driveway, or public walkway, the risk associated with advanced decay increases. A certified arborist can perform a thorough risk evaluation using specialized tools to determine the extent of internal decay and recommend the safest course of action.