Symptom Identification and Integrated Control Methods for Tomato Leaf Mold

Tomato leaf mold is a common fungal disease in tomato production, caused by infection with the leaf mold fungus (Passalora fulva). It mainly damages the leaves, and in severe cases can also spread to the petioles, stems and floral organs. The disease is especially widespread in protected cultivation such as greenhouses and plastic tunnels, and is one of the important diseases affecting the yield and quality of greenhouse tomatoes.

In the early stages of the disease, pale yellow chlorotic spots with indistinct edges appear on the upper surface of the leaves, while a grayish-white to grayish-brown mold layer forms on the corresponding parts of the underside, which is the typical feature for identifying leaf mold. As the disease develops, the lesions continue to expand and the mold layer gradually darkens; the leaves curl and wilt from the bottom upward, and in severe cases the leaves of the whole plant dry up and drop off, and the plant's photosynthetic capacity declines markedly.

Leaf mold favors warm, humid environments. Poor ventilation in the greenhouse, excessive watering, overly dense planting and insufficient light all favor the occurrence and spread of the disease. Soil in continuously cropped plots and greenhouse frames carry more residual fungal spores, so the disease often appears earlier and causes more severe damage, requiring special attention.

For control, agricultural measures should be combined with chemical control. Disease-resistant varieties can be selected, and seeds should be disinfected before sowing; crop rotation should be practiced, avoiding continuous cropping with solanaceous crops as far as possible; rational close planting and timely pruning and removal of side shoots will enhance ventilation and light penetration in the greenhouse; watering should be controlled scientifically, using drip irrigation or under-film irrigation to reduce air humidity. Diseased leaves found should be removed promptly and taken out of the field for proper disposal; in the early stages of the disease, appropriate chemicals should be selected for spray control, with attention paid to rotating the chemicals used to delay the development of fungal resistance.