Alternaria blight

The causative agent of the disease is the microscopic fungus Alternaria chartarum, which belongs to the class of deuteromycetes. It is an opportunistic pathogen that typically manifests as a saprotroph but transitions to active parasitism when plant defenses are compromised. It infects plant tissues at various stages of growth by entering through stomata or mechanical injuries.

This fungal species is identified on a wide range of agricultural crops, including cereal grains, vegetables (such as tomatoes and potatoes), and industrial crops. Alternaria chartarum frequently colonizes plant debris, making such organic matter the primary reservoir of infection within the soil and on field surfaces throughout the winter season.

Symptoms of the disease manifest as dark spots covered with a characteristic olive-colored or black fungal mycelium and conidia. As the infection progresses, these spots enlarge, causing chlorosis, premature senescence of leaf tissues, and fruit deformation. In high-humidity conditions, affected plant parts decay rapidly, leading to significant yield losses for producers.

The development of the infection is favored by moderately warm temperatures (between +20°C and +28°C) and high relative humidity. Frequent rainfall, heavy dew, and fog provide ideal conditions for conidia germination. Infection typically occurs during periods of plant stress, when the crop's natural defenses are weakened due to poor agricultural practices or unfavorable weather patterns.

Effective management and control of Alternaria chartarum require a comprehensive strategy combining agronomic and chemical methods:

• Implementing crop rotation to avoid planting susceptible crops consecutively.
• Thorough removal and disposal of crop residues after harvesting.
• Application of systemic and contact fungicides during active growing stages.
• Utilization of resistant cultivars and hybrids adapted to specific regional climates.
• Managing greenhouse humidity and maintaining optimal plant density to ensure air circulation.