Tulip gray bulb rot

The causative agent of the disease is the fungus Rhizoctonia tuliparum, a soil-borne pathogen known for causing significant damage to various bulbous plants. It survives in the soil through the formation of sclerotia, which allow the fungus to remain viable for several years, making it a persistent threat to garden beds and commercial fields.

The primary host for this fungus is the tulip, but it is also known to infect other spring-flowering bulbs such as hyacinths and irises. The infection usually occurs during the cool, wet periods of early spring or late autumn, often leading to total loss of the planting material if left unmanaged.

Symptoms often manifest as the failure of shoots to emerge from the soil. When diseased bulbs are unearthed, they typically show irregular, sunken brown lesions on their scales. A white or greyish fungal mycelium often appears on the surface of the infected bulb, eventually leading to a complete breakdown and rotting of the entire bulb tissue.

Environmental conditions that favor the development of Rhizoctonia tuliparum include high soil moisture and cool temperatures, usually between 10°C and 15°C. The pathogen is primarily spread through the movement of contaminated soil, infected bulbs, and the use of unsterilized gardening tools that carry fungal structures from one area to another.

To mitigate the risks of gray bulb rot, rigorous crop rotation is essential, ensuring that bulbs are not replanted in the same location for several years. Preventive measures should include the careful inspection of bulbs before planting, soil solarization or chemical sterilization, and the application of appropriate systemic fungicides as a seed treatment to prevent early infection.