Sclerotial rot of bulbs

The causal agent of this disease is the fungus Sclerotium wakkeri (also known as Stromatinia wakkeri). This soil-borne pathogen produces sclerotia, which are compact masses of hardened fungal mycelium that serve as long-term survival structures, allowing the disease to persist in the field for several years.

The primary hosts of this fungus are bulbous plants, most notably species of the genus Tulipa. The infection typically initiates when the fungus, present in the soil, colonizes the bulb scales or the basal plate of the plant during the early stages of spring growth.

Symptomatology involves the development of a white, cottony mycelium on the bulb surface. As the infection progresses, the tissues become necrotic and soft, eventually leading to the complete decay of the bulb. The formation of small, black sclerotia on the decaying plant tissues is a key indicator for field diagnosis.

The development and spread of Sclerotium wakkeri are heavily dependent on environmental conditions, specifically high soil moisture and cool temperatures. These factors stimulate the germination of sclerotia and facilitate the rapid movement of the mycelium through the soil profile, often aided by poor drainage.

The economic impact of this pathogen is significant due to the total loss of bulbs and poor establishment of crops. Integrated pest management strategies, such as crop rotation, use of certified healthy planting stock, and appropriate chemical seed treatments, are essential to minimize the spread and severity of the disease.

• Inspection of bulbs prior to planting for signs of rot.
• Implementation of long-term crop rotation cycles.
• Soil sterilization in severely infested areas.
• Application of systemic fungicides as a preventive treatment.