Tomato Leaf Mold
Passalora fulva (Cladosporium fulvum)
Overview
A fungal disease primarily affecting greenhouse tomatoes, causing olive-green to brown velvety patches on leaf undersides with corresponding yellow spots on upper surfaces. Tomato Leaf Mold spreads mainly by spores on wind, splash, tools, and crop debris. Humid, crowded plantings and overhead watering favor outbreaks in home gardens and food forests. Causal agent: Passalora fulva (Cladosporium fulvum). In regenerative gardens, prioritize sanitation, airflow, and unbroken soil cover over calendar spraying, and intervene early when symptoms appear.
Symptoms
Pale yellow spots on upper leaf surfaces. Olive-green to brown velvety mold on corresponding leaf undersides. Leaves curl, wither, and drop. Rarely affects fruit. Most severe in humid greenhouse conditions. Compare several plants and note whether symptoms spread after rain, insect feeding, or wet foliage. Photograph undersides of leaves and cut stems when wilt is present to refine the diagnosis. Rule out simple drought, fertilizer burn, and herbicide drift before assuming a pathogen - abiotic injury often mimics disease.
Environmental Conditions
Humid
Prevention
Ensure good ventilation in greenhouses. Reduce humidity. Plant resistant varieties. Avoid overhead watering. Space plants for air circulation. Remove lower leaves. Mulch to reduce splash, clear season-end debris, and avoid working plants when wet. Design beds for airflow and diverse plantings that support beneficial insects without creating permanent humid pockets around susceptible crops.
Management
Improve ventilation and reduce humidity. Remove infected leaves. Apply copper or chlorothalonil fungicides. Resistant varieties are the best long-term solution. Prefer drip irrigation, morning watering, and open spacing so leaves dry quickly. Disinfect pruners between cuts on woody plants. Use copper, sulfur, or biological products only as labeled protectants when pressure is high - they rarely reverse advanced infections alone. Destroy (do not casually compost) highly infectious debris.