Narcissus fire

The fungus Sclerotinia polyblastis (syn. Botryotinia polyblastis) is the causal agent of the disease commonly known as Narcissus fire. This fungal infection is a significant concern for flower bulb production, as it directly damages the reproductive organs of the plants.

The primary host for this pathogen is the Narcissus species. While it primarily attacks the flowers and flower stalks, the disease can significantly reduce the overall vigor of the bulbs by disrupting the photosynthetic cycle through premature leaf senescence and flower blight.

Symptoms appear as small, water-soaked spots on the flower buds that rapidly enlarge and turn dark brown or black. In high humidity, the tissues soften and collapse. Unlike other fungal diseases, the infection often leads to the complete blighting of the bloom before it has a chance to open fully.

The development of the disease is highly dependent on environmental conditions, specifically persistent cold and wet weather during the spring months. The fungus survives in the soil as sclerotia, which germinate to produce apothecia that release ascospores, spreading the disease to emerging flower buds.

Effective management strategies rely on a combination of cultural practices and chemical control. Growers should focus on removing infected debris, improving air circulation between plants, and applying protective fungicides during the early stages of bud development to prevent the initial stages of spore infection.