Botrytis neck rot of onion

Neck rot, primarily caused by the fungal pathogen Ciborinia allii (historically referred to as Botrytis allii), is one of the most destructive diseases affecting bulb crops globally. This pathogen leads to severe post-harvest losses, significantly reducing the marketability and shelf life of onions and garlic crops.

The disease primarily targets onions, shallots, and garlic. The fungus overwinters as small, hard, black structures called sclerotia, which can persist in the soil for several years or survive on infected debris, serving as the primary source of inoculum for subsequent growing seasons.

Initial symptoms are often invisible during the growing phase, but as the bulbs mature or are placed into storage, the neck area becomes soft and watery. Eventually, the bulb tissues collapse, and a characteristic gray, fuzzy mold (conidial mass) develops, often accompanied by the emergence of black, crust-like sclerotia on the affected surface.

Development and spread are heavily influenced by environmental conditions, particularly high humidity and moderate temperatures ranging from 15°C to 20°C. Infection typically enters the bulb through the neck during the late stages of growth, especially if the weather is cool and damp during the harvesting window, which prevents the neck from drying properly.

Management strategies focus on prevention: practicing strict crop rotation, ensuring proper field drainage, and avoiding excessive irrigation toward the end of the season. Post-harvest, it is essential to cure the bulbs thoroughly at warm, well-ventilated conditions before moving them into cold storage to inhibit the growth of the pathogen.

• Using disease-free planting material.
• Maintaining proper spacing to ensure good airflow.
• Sanitation by removing and destroying infected plant debris.
• Proper curing processes after harvest.
• Strategic fungicide applications during high-risk periods.