Actinomycosis of plants

Actinomycosis of plants is a bacterial disease complex caused by microorganisms belonging to the family Actinomycetaceae. These Gram-positive bacteria are unique due to their filamentous branching growth, which resembles fungal mycelium. This disease primarily affects the underground parts of plants, manifesting as localized tissue damage that compromises both yield quality and marketability.

The disease targets various root and tuber crops, with potatoes being the most frequently impacted. Common scab, a condition caused by various Streptomyces species within the family, is the most recognized agricultural consequence. The pathogen resides in the soil and infects the plant through lenticels, root hairs, or mechanical skin wounds during early development.

Symptoms are easily identifiable as corky lesions, scabs, or deep crater-like pits on the surface of the tubers and roots. These lesions vary in appearance based on the host cultivar and environmental conditions, ranging from shallow, flat spots to deep, necrotic cavities. The presence of these lesions negatively affects the commercial grade of the product and increases susceptibility to rot during long-term storage.

The development of the disease is highly dependent on environmental factors, particularly soil conditions. Actinomycetes thrive in warm, dry soils with a neutral to alkaline pH, typically ranging between 6.0 and 8.0. Agricultural practices that increase soil pH, such as excessive lime application, create favorable environments for these pathogens to flourish.

Effective management and protection strategies include:

• employing balanced crop rotation to reduce pathogen buildup;
• maintaining soil acidity with a pH level below 5.5;
• using physiological acidic fertilizers to suppress bacterial growth;
• selecting resistant varieties and healthy, certified seed material;
• implementing proper irrigation management to maintain soil moisture during the tuberization period.