Tomato leaf mold

Tomato leaf mold, caused by the fungus Fulvia fulva (syn. Cladosporium fulvum), is a destructive plant disease primarily affecting tomato crops. It is a major concern in protected cultivation environments such as greenhouses, where humidity and temperature conditions often align with the pathogen's optimal requirements for infection.

While tomatoes are the primary host, the disease can affect other solanaceous plants. The pathogen is particularly problematic in greenhouses because it requires high relative humidity to thrive. In outdoor settings, the disease is less common but can occur during periods of prolonged warmth and rain, leading to localized outbreaks that can spread rapidly through a field.

Symptoms typically begin on the lower leaves. Small, pale green or yellow spots appear on the upper surface of the leaves. Correspondingly, a velvety, olive-brown to grayish fungal growth develops on the undersides of these leaves. As the disease progresses, these spots enlarge, merge, and eventually cause the leaves to turn yellow, wither, and drop off prematurely, severely impacting the plant's photosynthetic capacity.

The development of Fulvia fulva is driven by environmental conditions. Relative humidity above 85% and temperatures ranging between 20°C and 25°C are ideal for spore production and germination. The spores are easily dispersed by air currents, splashing water, and handling, making strict sanitation protocols essential for managing the disease in commercial operations.

The economic impact of leaf mold is significant, as it leads to reduced fruit set, smaller fruit size, and weakened plants prone to other stresses. Effective management relies on an integrated approach to minimize the pathogen's spread and improve plant resistance:

• Utilizing resistant tomato cultivars or hybrids.
• Maintaining proper greenhouse ventilation and humidity control.
• Practicing strict crop hygiene, including the removal of infected plant debris.
• Applying fungicides labeled for leaf mold control when infection pressure is high.
• Implementing wide plant spacing to improve air circulation and reduce leaf wetness.