Penicillium bulb rot

The causative agent of this plant disease is the fungus Penicillium albocoremium. It is a common necrotrophic pathogen known to colonize bulbs and corms of various ornamental and agricultural plants. This fungus exploits damaged or weakened plant tissues, causing significant economic losses, especially during long-term storage periods.

Primary hosts for this pathogen include popular bulbous plants such as tulips, hyacinths, lilies, and irises. While the disease primarily affects stored bulbs, the infection can be transferred to the soil, where it poses a risk to emerging seedlings, often leading to poor stand establishment and reduced vigor of the future crop.

The visual symptoms of the infection involve the appearance of soft, brownish, or water-soaked lesions on the scales of the bulb. As the disease progresses, the typical mass of conidia develops on the surface, forming a dense white, pale yellow, or greenish mold. In advanced stages, the internal tissue of the bulb becomes completely degraded and loses its structural integrity.

The development of Penicillium albocoremium is strongly favored by high humidity (relative humidity above 80%) and temperatures that are not ideal for plant dormancy. Poor ventilation in storage crates exacerbates the spread of airborne conidia from infected bulbs to healthy ones, leading to rapid disease transmission throughout the entire batch of planting material.

Effective management and prevention strategies against this rot include several key practices:

• Ensuring bulbs are properly cured and dried before placement in storage.
• Implementing strict sanitation by removing and destroying any bulbs showing early signs of mold.
• Maintaining optimal storage conditions with low humidity and high air circulation.
• Applying prophylactic fungicide treatments to the bulbs before planting to protect them from soil-borne inoculum.