Onion disease control starts with symptom identification and field management

Onion disease control refers to the preventive and curative measures taken against common diseases such as downy mildew, purple blotch, gray mold and soft rot throughout the entire growing period of onions. Onion leaves and bulb tissues are tender, and once infected, the disease spreads easily, so doing a good job of control is crucial to ensuring yield and quality.

Identifying the disease is the first step in control. Downy mildew mostly shows pale yellow lesions on the leaves, with a grayish-purple mold layer on the surface when humidity is high; purple blotch appears as purple-brown spots with a lighter center and concentric rings; soft rot softens the bulb and makes it smell foul, mostly occurring when the field is waterlogged or during storage in damp conditions.

Agricultural control is the foundation. When planting, a rotation of two to three years or more should be practiced, avoiding successive cropping with onion and garlic crops; choose varieties with better disease resistance, adopt high-ridge cultivation and pay attention to drainage, and plant at a reasonable density to enhance ventilation and light penetration. In fertilization, control the amount of nitrogen fertilizer and appropriately supplement phosphorus and potassium fertilizer so that the plants grow vigorously and improve their own disease resistance. Diseased plants found in the field should be pulled out promptly and taken out of the field for proper disposal to reduce the spread of pathogens.

In the early stage of the disease, the corresponding fungicide can be selected for spraying control according to the symptoms, and attention should be paid to rotating the drugs to avoid the pathogen developing resistance. After harvest, dry thoroughly in the sun, and keep storage ventilated and dry, which can also effectively reduce problems such as rotting during storage.