Anthracnose

The first sign of infection is the appearance of small chlorotic spots on leaves, which eventually turn brown or dark tan. The center of the spot often becomes lighter, while a distinct dark or purple margin forms around the edges.

On affected stems, elongated lesions form, which may girdle the shoot, causing it to wilt and subsequently leading to the death of the upper part of the plant. Under high humidity, pink or orange spore pads become clearly visible on the surface of the spots.

When fruits are infected, sunken spots appear, which expand rapidly, turning the flesh into rot. Eventually, the fruits mummify, losing all their market quality and becoming a source of secondary infection.

The root system can also suffer from the pathogen in some cases, which manifests as general growth inhibition, yellowing of lower leaves, and slowed vegetative processes, often misidentified as nutrient deficiencies.

• Appearance of dark sunken spots on plant organs
• Presence of concentric zones within affected areas
• Formation of pink spore masses under high humidity
• Curling and premature leaf drop

The causative agent of this disease is the fungus Colletotrichum walleri, belonging to the group of imperfect fungi within the Coelomycetes class. This pathogen specializes in attacking various plant parts, including leaves, stems, and fruits, by penetrating deep into plant tissues.

The fungal mycelium develops within the intercellular spaces, gradually destroying tissue structure and leading to necrosis. Reproduction occurs via conidia, which are formed in specialized structures called acervuli, often visible as tiny dark spots on the surface of affected areas.

The pathogen's life cycle is closely linked to plant debris, where the fungus can persist for extended periods, surviving unfavorable conditions. In soil or on fallen leaves, the pathogen activates when favorable temperature regimes return.

Conidia are primarily dispersed by rain splashes, wind currents, and contact with contaminated agricultural equipment. A high rate of primary infection allows the fungus to rapidly occupy large areas of plantations.

Studying the biology of Colletotrichum walleri is vital for building integrated protection systems, as this species shows high adaptability to changing environmental conditions and possesses a wide host range.

The development of anthracnose caused by Colletotrichum walleri is directly dependent on humidity levels and soil moisture. Optimal conditions for mass spore germination include humidity levels above 85-90% and moderately warm temperatures.

The temperature range from +20°C to +28°C is considered most favorable for active mycelial growth and pathogen sporulation. Under these values, the incubation period of the disease can be reduced to just a few days.

Dense crop stands, poor ventilation within the canopy, or foliage create a microclimate ideal for the rapid spread of the fungus. Lack of aeration leads to moisture retention on leaf surfaces, which is critical for infection.

Injuries caused by pests or mechanical damage significantly facilitate the penetration of Colletotrichum walleri spores into plant tissues, acting as entry points for the pathogen.

Frequent rainfall during the growing season and heavy morning dew significantly increase the risk of epiphytotics, especially if plants are in the stage of active flowering or fruit formation.

The main danger of anthracnose lies in a sharp decrease in yield and a deterioration in produce quality. Affected fruits become unsuitable for storage and transportation, quickly succumbing to secondary rotting.

Infection of young shoots leads to reduced photosynthetic activity, which weakens the plant and decreases its winter hardiness in perennial crops. Gradual defoliation deprives the plant of energy required for fruit development.

When field or vegetable crops are affected, the disease can lead to the total loss of marketable yield. Economic damage includes direct loss of produce and costs for emergency additional fungicide applications.

The fungus releases toxins during its life cycle that poison plant tissues, causing systemic metabolic disorders. This leads to premature aging and death of individual organs or the entire organism.

Beyond direct damage, the presence of infection on a plot creates a long-term reservoir that requires strict phytosanitary measures in subsequent seasons to prevent disease recurrence.

The foundation of protection lies in using healthy seeds and planting material that are free from fungal infection. Seed treatment with systemic fungicides before sowing can eliminate surface-borne inoculum.

An important agronomic practice is maintaining crop rotation, which excludes the return of susceptible crops to the same area for at least 3-4 years. This allows the pathogen in the soil to lose its viability.

Destroying plant debris after harvest through deep plowing or burning (in accordance with fire safety regulations) removes the fungus's overwintering substrate and lowers the inoculum pressure in the soil.

Chemical control includes applying contact and systemic fungicides during critical plant growth stages. Applications should be performed prophylactically, without waiting for the first signs of leaf infection.

Maintaining optimal planting density and timely weeding promote better aeration of the plantations. Using varieties with genetic resistance to anthracnose is the most economically efficient method for long-term control.