clerotinia sclerotiorum

Sclerotinia, often referred to as white mould or stem rot, is a devastating soil-borne disease that affects a wide variety of vegetables and herbs, particularly beans, tomatoes, lettuces, brassicas, and sunflowers. It appears as a soft, watery rot near the base of stems or on infected leaves, often followed by white cottony fungal growth and the development of hard, black resting structures called sclerotia. These sclerotia remain dormant in the soil for years, waiting for the right moisture and temperature conditions to infect again.

For home gardeners, Sclerotinia outbreaks can be both heartbreaking and persistent. Once established, this disease is difficult to eliminate, and crop losses can be extensive. It often strikes just before or during harvest when plants are at their most productive. Prevention is the only practical option for organic growers, as conventional chemical treatments are off-limits and usually ineffective once infection has begun.

To reduce the risk, avoid overhead watering and ensure good spacing between plants to promote airflow. Remove all crop residues after harvest and rotate crops carefully—never plant susceptible crops in the same area two seasons in a row. For high-risk crops, pre-treatment of soil with beneficial organisms that parasitise or compete with the Sclerotinia fungus can help reduce pressure before symptoms appear. For best protection, use a biological soil treatment in advance of seasonal outbreaks.

• Biologicals

  
  Sclerostop
  Formulated with Coniothyrium minitans, a natural parasite of Sclerotinia sclerotia. Reduces disease pressure when applied preventatively in moist soils before canopy closure.

Note: Apply Sclerostop early, before symptoms appear. Rotate with Eco-77 or AmyProtec 42 to maintain soil health and reduce long-term inoculum levels. Avoid planting susceptible crops repeatedly in the same bed and destroy all infected plant material.