Gummy stem blight

Pathogen and disease type: Gummy stem blight, caused by the fungus Stagonosporopsis cucurbitacearum (formerly Didymella bryoniae), is a devastating fungal disease affecting cucurbit crops. The pathogen is highly infectious and attacks plants at all growth stages, significantly impacting both yield quantity and quality.

Host plants: This disease affects various members of the Cucurbitaceae family. Cucumber, melon, watermelon, squash, and pumpkin are particularly susceptible. The disease is common in both greenhouse environments and open field production, especially where climatic conditions are conducive to fungal growth.

Symptoms and signs: The disease manifests as leaf spots that initially appear as small, dark, water-soaked areas that expand into large, irregular necrotic lesions. Stem infections are particularly dangerous, appearing as tan-to-brown lesions that often exude a gummy substance. Tiny black pycnidia develop within the dead tissues as the disease progresses.

Conditions for development: Stagonosporopsis cucurbitacearum thrives in warm and humid conditions, with temperatures ranging from 15°C to 25°C being optimal. High humidity, frequent rainfall, or sprinkler irrigation promotes the rapid release and dissemination of fungal spores throughout the crop field.

Harmfulness and prevention: The pathogen is responsible for substantial economic losses, causing wilting, plant collapse, and fruit rot. Effective management strategies involve integrating cultural practices, such as crop rotation, use of disease-free certified seeds, sanitation of infected crop debris, and the timely application of systemic or contact fungicides.

• Proper greenhouse ventilation to reduce humidity levels.
• Removal and destruction of infected plant material.
• Use of disease-resistant or tolerant cultivars.
• Regular scouting for early detection of necrotic symptoms.