Sclerotinia Stem Rot (White Mold)
Sclerotinia sclerotiorum
1 host plant
Last updated
This profile synthesizes data from multiple published sources. Expert field review is in progress.
Sclerotinia stem rot and white mold cause stem decay and white fungal growth on affected plants. Remove infected plant material. Improve air circulation through spacing and pruning. Avoid overhead watering and reduce humidity. Rot diseases are difficult to manage once established. Focus on prevention through proper culture and site selection Early detection and prompt management of symptoms help limit disease spread.
Reduce moisture around affected tissue by improving drainage and air circulation. Remove rotted material cleanly and dispose of it away from the planting area. Avoid wounding healthy tissue during cleanup, as fresh wounds create new entry points. If the problem keeps returning, evaluate whether the site is too wet or poorly drained for the species you are growing.
Quick Reference
Management
Spring through early summer (April-June in Puget Sound region) during cool, wet weather when apothecia are active. Extended risk in seasons with frequent rain and cool temperatures. Flowers and young tender growth most susceptible.
Cool, wet conditions (59-70°F optimum, 50-75°F range); extended leaf wetness or high humidity >85%. Infection requires free moisture. Apothecia develop and release spores primarily in spring; can produce spores over several weeks. Soil moisture, mulch presence, and plant density all favor apothecial development. Overfertilization producing tender, succulent growth increases susceptibility. # Source: PNW Plant Disease Management Handbook
Cultural Controls
- Prevent mechanical injury to trees, especially late in the season.
- Avoid leaving trees on the ground during rainy winter weather.
- Plant on well-drained sites and avoid mounding soil around trunks.
- Harvest highly susceptible nursery trees during dry weather.
- Remove and destroy all infected plants and fallen plant material.