Sclerophoma stem rot of eustoma

Pathogen and disease type. Sclerophoma eustomatis is the causal agent of a specific fungal disease affecting the stems of Eustoma plants. This pathogen belongs to the group of fungi that cause necrotic lesions in plant tissues. It is a specialized parasite that primarily targets the vascular system, leading to rapid decline in plant health once the infection becomes systemic.

Host plants. The primary host for this fungus is Eustoma russellianum. The disease is frequently observed in nursery production, where high density and environmental factors facilitate the spread of spores. Both container-grown Eustoma and field-grown plants are susceptible to this pathogen at various stages of their development.

Symptoms and signs. The initial symptoms include the development of light-colored, watery lesions on the stems. As the fungus advances, these areas turn dark brown or grey and become sunken. A critical diagnostic feature is the presence of pycnidia, appearing as tiny black dots on the surface of the infected tissue, which release conidia under high humidity conditions.

Developmental conditions and impact. The development of Sclerophoma eustomatis is highly favored by high ambient humidity and moderate temperatures. Lack of proper air circulation within greenhouses accelerates the spread of the fungus. The economic impact is severe, as infected plants often exhibit wilting, reduced flowering, and may eventually collapse entirely due to stem girdling.

Protection and prevention. Managing this disease requires a preventative approach focused on environmental sanitation:

• Remove and destroy infected plant debris promptly to reduce the inoculum source.
• Ensure adequate spacing between plants to maximize airflow around the stems.
• Maintain low humidity levels in the greenhouse environment, particularly during nighttime.
• Apply preventive systemic fungicides when the climate conditions favor fungal development.