Sclerotinia subarctica

Pathogen and disease type. Sclerotinia subarctica is a fungal pathogen responsible for causing white mold or sclerotinia stem rot. This pathogen is known for its ability to produce sclerotia, which are hard, melanized survival structures. These structures allow the fungus to persist in the soil for several years, waiting for favorable environmental conditions to germinate and infect new host plants.

Affected crops. The host range of this fungus primarily includes Solanaceae and Apiaceae plant families. It is particularly notorious for damaging potato crops and carrots. Due to its biological adaptability, it can be found in various regions, impacting both commercial agricultural fields and domestic gardens where environmental conditions favor its growth.

Symptoms and signs. The characteristic symptoms begin with the appearance of water-soaked spots on stems or leaves, which rapidly expand. Under conditions of high humidity, a thick, white, cottony mycelium develops over the infected areas. Over time, this mycelium develops into hard, black sclerotia. Infected plants typically exhibit wilting, stem collapse, and rotting, often leading to total death of the foliage.

Conditions for development and impact. The pathogen thrives in cool, moist environments, which are conducive to mycelial growth and sclerotia germination. The damage is profound, as the fungus degrades plant tissues, disrupting water and nutrient transport. Economic impact is severe, particularly because the pathogen can spread rapidly in storage facilities, leading to major post-harvest losses if contaminated crops are stored together.

Protection and prevention measures. Managing Sclerotinia subarctica requires a systematic approach to break the infection cycle and minimize inoculum pressure:

• Implement long-term crop rotation cycles to starve the pathogen.
• Deep plowing to bury sclerotia, preventing them from germinating near the surface.
• Ensure adequate plant spacing to promote airflow and reduce canopy humidity.
• Apply registered fungicides during high-risk weather windows (prolonged rain).
• Sanitize storage facilities to prevent the spread of sclerotia among healthy tubers.