Sclerotinia

Sclerotinia sclerotiorum is a highly destructive plant pathogenic fungus belonging to the kingdom Fungi and the genus Sclerotinia. It is a cosmopolitan polyphage capable of infecting over 400 plant species, including major crops like sunflowers, oilseed rape, and soybeans. The fungus is best known as the causative agent of white mold, a disease that can devastate agricultural productivity.

The primary symptom of the disease is the appearance of fluffy, white fungal growth on stems, leaves, and reproductive structures. As the infection progresses, the mycelium forms dense, black, irregular bodies called sclerotia. These structures allow the fungus to persist in soil for many years, causing structural collapse and tissue decay in the host plant, often leading to rapid wilting and death.

The life cycle of the pathogen is centered around the survival and germination of sclerotia in the soil. Under favorable moisture and temperature conditions, sclerotia germinate to produce apothecia — small, cup-shaped fruiting bodies. These fruiting bodies discharge millions of ascospores into the air, which are then wind-dispersed to infect healthy plant tissues, particularly during the flowering stage.

Development and spread of the pathogen are driven by high humidity and moderate temperatures ranging from 15°C to 25°C. Dense plant canopies and periods of prolonged rainfall create a microclimate conducive to rapid infection. In the field, the presence of these factors often leads to epidemic outbreaks, especially if the crop canopy remains wet for extended periods during bloom.

Integrated disease management (IDM) is the most effective approach for managing Sclerotinia infections:

• Implementation of crop rotation using non-host crops like cereals.
• Deep tillage to bury sclerotia, reducing their ability to germinate at the surface.
• Use of high-quality, certified, pathogen-free seeds.
• Application of targeted fungicides during critical growth stages, specifically when infection risk is highest at flowering.