Cucumber scab

The causal agent of this plant disease is the fungus Cladosporium cucumerinum, which is commonly known as cucumber scab. This pathogen is particularly prevalent in humid greenhouse environments and can cause severe damage to the fruit, making them unmarketable and susceptible to secondary bacterial decay.

This disease primarily attacks cucurbits, including cucumbers, squash, pumpkins, and melons. While all aerial parts of the plant, such as stems and leaves, can be affected by the fungus, the most significant damage occurs on the fruits, where the symptoms are most distinct and economically devastating.

Symptoms on leaves start as small, water-soaked spots that eventually turn grey or brown, often becoming brittle and falling out. On fruits, the initial signs are small, sunken, water-soaked lesions that later develop into scab-like, corky areas covered with an olive-green, velvety mass of fungal spores.

The development of the fungus is highly dependent on environmental conditions, specifically high humidity and cool to moderate temperatures. Heavy dew and poor ventilation in greenhouses facilitate the rapid spread of spores through water splashes and air currents, allowing the disease to progress quickly during critical growth phases.

Managing the disease requires an integrated strategy, starting with the use of resistant cucumber cultivars. Cultural practices such as proper plant spacing, adequate ventilation, and precise irrigation are essential to lower humidity levels. Chemical control involves the application of fungicides, but prevention remains the most effective tool in maintaining a healthy crop.

• Practice crop rotation to avoid pathogen buildup in the soil.
• Maintain optimal greenhouse climate and airflow.
• Sanitize equipment and greenhouses after harvest.
• Remove and bury or burn all infected plant debris.