Oak bark necrosis (Dendrostoma leiphaemia)

The primary symptom of this disease is the formation of specific stroma of the fungus on the bark of infected trunks and branches. Initially, these appear as small bumps that eventually rupture the tree's epidermis.

In the affected areas, the bark takes on a grayish-brown hue and begins to die. Necrotic spots often have irregular shapes and can girdle the branches, leading to their gradual drying and death.

On the surface of the dead bark, numerous black dots can be observed; these are the fungal fruit bodies (perithecia) grouped into dense clusters. Under high humidity, spores emerge from them, creating a light-colored coating.

Infection often begins in the lower parts of the crown or at mechanical damage points on the trunk. Gradually, the disease spreads upwards, affecting healthier parts of the tree.

Prolonged development of the disease causes the oak crown to become sparse, leaves to shrink in size, and the tree to lose its biological stability and aesthetic appeal.

The causative agent of the disease is the ascomycete fungus Dendrostoma leiphaemia. It is a pathogen specialized in attacking broad-leaved trees, particularly oaks.

The fungus leads a predominantly parasitic lifestyle, developing within the tissues of the bark and phloem. It is capable of surviving for long periods in dead wood.

The life cycle includes the formation of sporulation during the summer-autumn period. Spores are dispersed by wind, rain droplets, and insects, infecting healthy trees through micro-cracks.

The mycelium of the fungus actively destroys the bark, penetrating the cambium and vascular tissues. This disrupts the normal flow of nutrients from the crown to the roots.

The biology of the pathogen allows it to develop actively during periods when the tree is weakened, making Dendrostoma leiphaemia a key factor in oak decline.

The most favorable conditions for the intensive development of the disease are periods with high air humidity and frequent rainfall. Wet weather facilitates active spore germination.

Weakened trees growing in poor soil conditions, suffering from moisture stress, or damaged by pests are most susceptible to infection by this fungus.

Mechanical injuries to the trunk, caused by animals, machinery, or natural disasters (hail, wind), serve as entry points for the infection.

Densely planted areas with poor aeration and lack of sunlight create a microclimate that promotes the rapid spread of fungal spores between neighboring trees.

The temperature range of moderately warm spring and autumn is considered optimal for fungal growth, making these seasons the most critical for disease spread.

This fungal disease poses a serious threat to forestry as it leads to mass branch mortality and premature drying of the entire tree.

The disease significantly reduces the technical quality of the wood, making it unsuitable for industrial use due to the development of necrosis and decay.

Infected trees become infection centers for healthy stands, contributing to the rapid spread of the fungus over large forest areas.

The drying of trees disrupts the ecological balance in the forest, alters the structure of the plant community, and reduces the overall productivity of the stands.

The disease is particularly dangerous for young seedlings and weakened specimens in parks and shelterbelts, where the decorative value of trees is highly significant.

The main method of prevention is maintaining a strict sanitary regime in the stands: timely felling and removal of infected trees and branches.

It is important to ensure optimal conditions for oak growth, including proper irrigation, fertilization, and pest protection, as insects often carry fungal spores.

When pruning trees, sterilized tools should be used, and pruning wounds should be treated with wound paint or fungicidal pastes.

In park zones, preventive spraying with fungicides during the growing season is permitted to prevent infection of healthy trees in disease hotspots.

• Conduct regular inspections for signs of necrosis.
• Dispose of diseased pruning debris by burning.
• Stimulate tree immunity with complex fertilizers.