Sclerotinia Crown and Stem Rot
Sclerotinia sclerotiorum, Sclerotinia minor
Overview
A soil-borne fungal disease causing crown rot, stem rot, and wilt in many crops. Produces white cottony mycelium and hard black sclerotia. Related to White Mold but primarily attacks the crown and lower stem. Sclerotinia Crown and Stem Rot spreads mainly by spores on wind, splash, tools, and crop debris. Humid, crowded plantings and overhead watering favor outbreaks in home gardens and food forests. Causal agent: Sclerotinia sclerotiorum, Sclerotinia minor. In regenerative gardens, prioritize sanitation, airflow, and unbroken soil cover over calendar spraying, and intervene early when symptoms appear.
Symptoms
Water-soaked lesions at the crown and lower stem. White, cottony mycelium on affected tissue. Hard, black sclerotia inside and on stems. Wilting and collapse. Lettuce drop (entire head collapses). Compare several plants and note whether symptoms spread after rain, insect feeding, or wet foliage. Photograph undersides of leaves and cut stems when wilt is present to refine the diagnosis. Rule out simple drought, fertilizer burn, and herbicide drift before assuming a pathogen - abiotic injury often mimics disease.
Environmental Conditions
Cool
Prevention
Rotate with non-host crops. Improve air circulation. Avoid dense planting. Reduce irrigation frequency. Apply Coniothyrium minitans to soil. Mulch to reduce splash, clear season-end debris, and avoid working plants when wet. Design beds for airflow and diverse plantings that support beneficial insects without creating permanent humid pockets around susceptible crops.
Management
Remove infected plants. Apply biological controls (Coniothyrium minitans). Improve drainage. Avoid overhead irrigation. Deep tillage to bury sclerotia. Prefer drip irrigation, morning watering, and open spacing so leaves dry quickly. Disinfect pruners between cuts on woody plants. Use copper, sulfur, or biological products only as labeled protectants when pressure is high - they rarely reverse advanced infections alone. Destroy (do not casually compost) highly infectious debris.