Pine macrodiplodiosis

The first and most noticeable symptom of pine macrodiplodiosis is premature yellowing, followed by browning and wilting of needles on current-year shoots. Affected needles often curl and drop prematurely, leading to significant thinning of the crown in the lower and middle sections.

On affected bark of shoots and needles, one can observe the formation of small black fungal fruiting bodies called pycnidia. They are often arranged in rows or groups, breaking through the epidermis of the plant.

As the disease progresses, necrosis of the bark on the shoots occurs, which can girdle the branch, causing it to dry out completely above the infection site. This creates a characteristic flagging effect or curling of the tops of young trees.

Under high humidity conditions, characteristic mucous secretions containing fungal spores may appear around the pycnidia, which are easily dispersed by wind and rain droplets to healthy parts of the tree.

The disease is often chronic, weakening the tree over several years, gradually leading to mortality if proper sanitary maintenance is not performed.

The pathogen responsible for the disease is the ascomycete fungus Macrodiplodiopsis desmazieri. This pathogen is a parasite that primarily attacks weakened coniferous trees.

The fungus leads a parasitic lifestyle, developing within the tissues of the bark and needles. Its life cycle includes an asexual stage (anamorph) where pycnidia with spores are formed, ensuring rapid spread of the infection during the growing season.

The infection persists as mycelium and spores within affected shoots, in fallen needles, and on dead branch bark, making the source of infection nearly impossible to eliminate without radical sanitary measures.

The fungal mycelium is capable of penetrating deep into wood tissues, causing metabolic disturbances and inhibiting photosynthesis, eventually leading to the death of the infected plant parts.

The biology of the pathogen is closely tied to the physiological state of the tree: the fungus activates when the pine's defense mechanisms are weakened by environmental stresses such as drought or air pollution.

The primary factor promoting the development of macrodiplodiosis is high relative humidity and frequent rainfall during the period of active pine shoot growth.

Dense forest stands, where normal air circulation is obstructed, create an ideal microclimate for fungal spore germination and subsequent host colonization.

Trees growing on poor, dry soils or experiencing nutrient deficiencies are much more susceptible to infection than healthy specimens in optimal sites.

A temperature range of +15 to +25 degrees Celsius is most favorable for rapid spore spread and the colonization of healthy shoots.

Mechanical injuries to needles and bark caused by pests (such as aphids or sawflies) create entry points for the infection, accelerating the process of disease development.

Macrodiplodiosis poses a serious threat to forestry, as it leads to mass drying of young trees and loss of timber value.

Severe crown damage reduces the annual growth of the tree, which over time leads to the degradation of stands and premature mortality.

In nurseries and ornamental landscapes, the disease ruins the appearance of plants, making them unsuitable for landscaping and sale, causing direct economic damage to owners.

Constant loss of needles weakens the tree, making it vulnerable to secondary pests such as bark beetles and wood borers, which finalize the destruction of the plant.

The spread of fungal spores within a forest area creates infection reservoirs that can exist for decades, constantly suppressing the natural regeneration of coniferous cultures.

The main preventive measure is strict adherence to forest pathology hygiene rules: regular removal and burning of affected, dead, and weakened branches.

When planting new stands, it is recommended to use disease-resistant species and forms of pine, and to avoid excessive stand density, ensuring proper aeration of the site.

In ornamental gardens and nurseries, spraying with copper-based fungicides or systemic pesticides during bud burst and active shoot growth is effective.

It is important to timely fertilize trees with complex fertilizers to increase their overall immune resistance to fungal diseases.

• Regular monitoring of needle condition.
• Sanitary crown pruning.
• Application of chemical protective agents at the first signs of disease.