Fusarium basal rot

Fusarium basal rot, often identified by the Latin name Fusarium oxysporum f. sp. cepae, is one of the most destructive soil-borne diseases affecting allium crops worldwide, including bulb onions and garlic. This fungal pathogen survives in the soil for extended periods, making it a persistent threat to agricultural land.

The disease primarily targets the root system and the basal plate of the bulb. While it can attack at any stage of growth, the symptoms often become more evident as the season progresses toward maturity. Infected plants show stunted growth, leaf chlorosis, and eventual wilting, which are classic signs of vascular system disruption caused by the fungus.

Visual inspection of the bulbs reveals a brownish rot that starts at the base and extends upward. Under high humidity, a characteristic white to pinkish fungal mycelium may develop on the rotted tissue. Affected bulbs often soften rapidly, leading to significant losses both in the field and during post-harvest storage.

Environmental conditions play a critical role in the development of the disease. The pathogen thrives in warm, moist soils, with optimal temperatures for growth ranging between 25°C and 30°C. Infection is frequently facilitated by wounds in the basal area caused by pests like onion maggots or nematodes, which provide an entry point for the fungal spores.

Effective management and prevention strategies include:

• Practicing strict crop rotation, ensuring a gap of at least 4–5 years between host crops.
• Improving soil drainage to avoid moisture accumulation around the roots.
• Utilizing disease-resistant cultivars when available in your region.
• Treating planting material with recommended fungicides prior to sowing.
• Removing and destroying infected plants to prevent the buildup of inoculum in the soil.