Arthoniaceae lichens

The color of these formations ranges from grayish and whitish to brownish shades. Unlike foliose species, crustose Arthoniaceae forms are extremely difficult to separate from the bark without damaging the living plant tissues.

Upon visual inspection, one can notice characteristic fruiting bodies called apothecia, which look like tiny black dots or streaks. Infestation often begins in the lower, more shaded part of the trunk and gradually spreads to the main scaffold branches.

Under high humidity, the lichen surface may acquire a slight greenish tint due to the activation of symbiotic algae. Colony development is extremely slow, but over time, they can cover significant areas of the bark.

It is important to distinguish lichens from pathogenic fungi that cause necrosis. Arthoniaceae lichens are epiphytes that derive nutrition from atmospheric sources without penetrating deep into the wood, but their presence always signals poor air circulation.

The causative agents are fungi from the Arthoniaceae family that live in symbiosis with green algae. This is a complex organism where the fungus provides protection and moisture retention, while the alga performs photosynthesis.

The condition is classified as a superficial epiphytic growth. In agronomic practice, such organisms are not considered parasites in the strict sense, as they do not feed directly on the tree's sap.

The fungus's life cycle involves the formation of apothecia, where spores mature. Spread occurs primarily via spores, which are carried by wind or raindrops onto suitable sections of bark.

Arthoniaceae species specialize in colonizing bark with a specific degree of roughness. They are most active in regions with temperate climates, where regular precipitation maintains the necessary moisture level on the trunk surface.

The biology of these organisms is closely tied to the host's bark condition. On young trees with smooth bark, lichens rarely settle, preferring older trunks with numerous micro-cracks where dust and moisture accumulate.

The main condition for the development of Arthoniaceae lichens is high air humidity in the orchard. In dense plantings where air circulation is restricted, a favorable microclimate for spore germination is created.

Lack of proper crown care contributes to their spread. Improper pruning or the absence of it leads to shading of the trunk, which prevents rapid moisture evaporation after rainfall.

Lichens most often settle on weakened trees with slowed metabolic processes. Old orchards, where bark is prone to natural aging and cracking, become an ideal substrate for the formation of large colonies.

Air pollution or proximity to natural water bodies can also stimulate epiphyte growth. Excessive bark moisture combined with a lack of direct sunlight creates a stable habitat.

The development of Arthoniaceae species slows down in dry climates and with regular ventilation of the area. Reducing the moisture of the trunk surface is a critical factor limiting their survival.

Although lichens are not direct parasites, their mass spread causes indirect damage to the orchard. They create a dense layer on the bark surface, which can interfere with the plant tissue's natural gas exchange.

Excess moisture often accumulates under the lichen layer, creating ideal conditions for secondary bacterial and fungal infections. The presence of lichens often becomes a "gateway" for dangerous pathogens.

Epiphyte colonies often become a shelter for pests such as scale insects, mites, and various weevils. Insects successfully overwinter in the folds of the lichen, which complicates their subsequent eradication.

The affected tree looks stunted, which reduces its decorative and commercial value. Reducing the intensity of photosynthesis in the trunk bark, which also participates in gas exchange, leads to a general decrease in the fruit tree's immunity.

In neglected cases, heavy lichen coverage can lead to premature death of individual branches. Constant dampness under the lichen cover provokes bark cracking and cambium damage from frost cracks.

The primary control method is regular mechanical cleaning of trunks and scaffold branches using scrapers or stiff brushes. Work is best done during the dormant period, in humid weather, when lichens are easier to detach.

To prevent recurrence, trunks should be whitewashed with high-quality garden paint or a lime solution mixed with copper sulfate. This creates an inhospitable environment for fungal spore attachment.

Thinning pruning of the crown is an important preventive measure. Ensuring light and air access to the central part of the tree drastically reduces the probability of bark colonization by epiphytes.

Chemical protection involves spraying trees with copper-based preparations, such as Bordeaux mixture or similar fungicides. Treatment is carried out in early spring or late autumn when air temperatures are above 5 degrees Celsius.

It is necessary to maintain high orchard maintenance standards: timely fertilization and irrigation strengthen the tree, promoting rapid bark growth, which hinders colonization by epiphytes. A healthy, actively growing tree is always less prone to lichen growth.