Clover rot

The disease is caused by the fungus Typhula trifolii, a basidiomycete responsible for a specific type of sclerotial rot. This pathogen specifically attacks the crown and lower stems of legume plants, with the infection cycle typically manifesting during late winter and early spring months.

The primary host for this fungus is clover, though it may also affect various other forage legumes. The pathogen is particularly destructive in regions with cool, wet climates where heavy snowfall provides a persistent insulating layer that protects the fungal mycelium, allowing it to thrive and spread across the field surface.

The most visible symptoms include a white or greyish cottony mycelium mat covering the crown area as the snow melts. As the disease progresses, the infected tissue becomes soft and eventually decays. The formation of small, round, dark brown or black sclerotia on the decaying stems is the definitive feature used for identification.

Fungal activity is favored by high soil moisture levels and temperatures near or slightly above freezing. The sclerotia of Typhula trifolii function as survival structures, remaining viable in the soil for several years and serving as the primary source of inoculum for subsequent cropping seasons if conditions allow.

Integrated management is essential for controlling Typhula trifolii and mitigating its economic impact on forage production:

• Implement a strict crop rotation schedule by avoiding host species for several years.
• Ensure proper field drainage to prevent water accumulation during winter months.
• Practice deep tillage to bury infected crop residues and inhibit fungal spread.
• Select resistant cultivars and ensure optimal planting densities to encourage air circulation.