Web blight

Web blight is a destructive plant disease caused by the fungal pathogen Ceratobasidium ramicola. This fungus is recognized for its ability to cause rapid tissue decay in a wide range of host plants, significantly impacting yield in commercial agriculture and reducing the aesthetic value of ornamental plants.

The pathogen is known to affect various important crops, most notably watermelon, where it can damage foliage and stems, and azalea, where it frequently causes blighting of leaves and twigs. The versatility of the pathogen allows it to infect plants in both open fields and greenhouses, especially when high-density planting is practiced.

The characteristic symptom is the appearance of water-soaked spots that quickly enlarge and turn necrotic. Under high humidity conditions, the presence of the fungus is confirmed by the development of white, web-like mycelial strands covering the affected leaf surfaces. Without intervention, this leads to widespread defoliation and plant death.

Environmental conditions are critical for the outbreak of Web blight. The pathogen thrives in warm temperatures (20-28°C) combined with high humidity levels exceeding 85%. Poor air circulation and the presence of free water on plant surfaces act as primary drivers for the germination of fungal spores and their subsequent spread across the plant canopy.

Managing Web blight requires an integrated approach to reduce environmental pressure and fungal load:

• Improving air circulation through wider spacing and strategic pruning.
• Implementing drip irrigation to keep foliage dry.
• Removing and destroying infected plant debris to reduce soil-borne inoculum.
• Applying recommended fungicides at the onset of favorable environmental conditions.
• Maintaining field hygiene by cleaning tools and machinery after use.