Penicillium rot of bulbs

Penicillium hirsutum is a pathogenic fungus responsible for the Penicillium rot of bulbous plants, a destructive disease that primarily affects the quality of stored bulbs. This fungus is a ubiquitous soil-borne and storage pathogen that can compromise the viability of high-value bulbous crops.

The disease frequently targets ornamental species such as tulips, lilies, hyacinths, and daffodils, as well as edible crops like garlic. The pathogen takes advantage of weakened tissues, particularly those damaged during mechanical harvesting or handling, to establish an infection that can destroy entire storage batches.

Symptoms of the infection manifest as the appearance of a powdery, blue-green to grayish-green fungal growth on the surface of the bulbs. Underlying tissues become soft, discolored, and watery, eventually leading to a complete breakdown of the bulb structure and a characteristic musty, sour odor associated with fungal decay.

Favorable conditions for the development of the fungus include high humidity (above 80%), poor air circulation in storage units, and storage temperatures that fluctuate significantly. These factors facilitate rapid sporulation and the spread of spores to healthy bulbs through direct contact or air currents.

Management strategies for controlling Penicillium rot emphasize prevention and hygiene. Key practices include:

• Careful harvesting to minimize mechanical damage to the bulb skin.
• Drying bulbs thoroughly before storage to reduce surface moisture.
• Maintaining well-ventilated storage conditions with controlled temperature and humidity.
• Using systemic fungicide dips for pre-storage treatment of the planting stock.