Cladosporium leaf mold

Cladosporium leaf mold is a destructive fungal disease caused by pathogens of the Cladosporiaceae family, with Cladosporium fulvum being the most prominent species attacking tomatoes. This disease is particularly prevalent in greenhouse environments where high humidity levels favor the rapid dispersal of fungal spores.

Initial symptoms include pale green or yellowish spots on the upper side of the leaves. As the disease progresses, these spots expand, and a velvety, olive-brown mass of spores develops on the underside of the leaf. Severe infections cause the foliage to wither, turn brown, and eventually drop off, weakening the entire plant.

The development of the fungus is highly dependent on environmental conditions, specifically high relative humidity (above 85%) and temperatures between 20°C and 25°C. The spores are easily dispersed by wind, water splashing, or contaminated tools, allowing the infection to spread rapidly throughout a crop canopy.

The economic impact of leaf mold is significant, as it leads to reduced fruit set, smaller fruit size, and poor quality of the harvest. In severe cases, particularly in unventilated greenhouse structures, the loss of photosynthetic leaf area can lead to a total collapse of plant health and significant yield reductions.

Effective management requires an integrated approach. Essential practices include:

• maintaining proper greenhouse ventilation to lower humidity;
• pruning lower leaves to improve air circulation;
• selecting disease-resistant cultivars;
• sanitizing equipment and removing crop residues;
• applying approved fungicides during the early stages of infestation.