White rot, or sclerotinia (Sclerotinia sclerotiorum), is a fungal disease that affects more than 500 species of cultivated and wild plants. The main host crops are sunflower, soybean, rapeseed, and corn.
A characteristic feature is a white felt-like coating on the affected plant tissues.
🔍 What is sclerotinia
Sclerotinia is a fungal disease caused by the polyphagous Sclerotinia sclerotiorum (Lib.) de Bary.
During its development cycle, the fungus forms sclerotia — dense black formations that remain viable in the soil for up to 10 years.
Type of infection: soil-borne.
Main danger: damage to all vegetative parts of the plant — from the root to the basket.
🌍 Spread of white rot
The disease is widespread in all climatic zones, but causes the most damage in regions with high humidity and cool springs.
Risk factors:
- frequent precipitation, fog, heavy dew;
- lack of crop rotation;
- saturation of fields with susceptible crops (sunflower, soybean, rapeseed).
🕐 When white rot manifests itself
The infection can manifest itself at any stage of vegetation.
Main forms of damage:
- Root form
The root system softens, rots, and becomes covered with a white coating. Young plants may not sprout.
- Stem form
Brown spots appear at the base, the tissues are destroyed, and the stem breaks. Black sclerotia form inside.
- Basket form
The most harmful form. The damage begins during the flowering phase. A wet spot appears on the back of the basket, gradually covering the entire basket and causing it to rot. The seeds become small and unviable.
⚠️ Consequences of white rot infection
- loss of young plants and thinning of crops;
- premature ripening;
- shrivelled seeds with low germination energy;
- yield reduction of up to 60% or more in outbreak years.
Biological threshold of harmfulness: 5% of destroyed baskets.
🔬 Source of infection
The main source of infection is fungal sclerotia that remain:
- in the soil,
- on plant debris,
- in seeds.
These structures retain their ability to germinate for 5–10 years.
🌱 How the disease develops
After harvesting, sclerotia remain in the soil.
At a humidity of 50–60% and a temperature of +18…+24 °C, they germinate, forming white mycelium.
Under favourable conditions, apothecia (fruit bodies) are formed, which release ascospores.
Ascospores are carried by the wind and infect neighbouring plants.
Optimal conditions for development:
- air humidity above 80%;
- temperature +18…+25 °C.
🧩 How to prevent sclerotinia
Effective preventive measures:
- adherence to optimal crop rotation;
- deep autumn ploughing;
- regulation of excessive crop density;
- cleaning seeds from sclerotia;
- pre-sowing seed treatment.
📉 Violation of these rules increases the risk of mass damage and reduces the quality of the harvest.
🧭 Conclusions for farmers
White rot is a long-term threat that cannot be eliminated in one go.
Only a comprehensive approach — agricultural technology + biological protection + high-quality seed material — will ensure a stable harvest and healthy fields.