Sclerotium rot

Sclerotium denigrans is a soil-borne fungal pathogen responsible for significant plant health issues, particularly focusing on root and stem decay. The fungus produces resistant structures called sclerotia, which are dark, durable, and capable of persisting in the soil for several growing seasons, making eradication extremely challenging for producers.

The host range for this pathogen is extensive, affecting numerous horticultural and agricultural crops. Vegetables such as tomatoes, peppers, and various leguminous species are particularly susceptible. In fields with poor drainage or intensive monoculture, the incidence of the disease tends to increase dramatically, leading to economic losses in yield and quality.

Symptoms typically manifest as sudden wilting of the foliage, despite adequate soil moisture. The basal stem area often exhibits water-soaked lesions that eventually develop into brown or black necrotic tissue. Close observation reveals white, thread-like mycelium, which later develops into small black sclerotia, giving the pathogen its characteristic dark appearance during the later stages of infection.

Environmental conditions play a critical role in the development of Sclerotium denigrans. The fungus thrives in warm temperatures, typically ranging from 20°C to 30°C, combined with high soil moisture levels. Poor air circulation and high humidity levels in greenhouses often accelerate the spread of the mycelium through the soil surface and between adjacent plants.

Management strategies must focus on prevention and sanitation to limit the spread of the pathogen. Key practices include:

• Implementing long-term crop rotation cycles.
• Improving soil drainage and bed ventilation.
• Removing and destroying infected plant debris.
• Applying fungicides specifically targeting soil-borne basidiomycetes.

Biological control, particularly the use of antagonistic fungi like Trichoderma species, has shown promise in suppressing the population of Sclerotium denigrans. Integrated pest management (IPM) remains the most effective approach, combining rigorous cultural practices with chemical or biological interventions to maintain crop health and minimize the impact of the disease on farm profitability.