Basal Rot - Southern Blight

Basal Rot or Southern Blight or Collar Rot or Sclerotium rot or White Mold, is caused by the fungus Sclerotium rolfsii.

Sclerotium rolfsii is an omnivorous soil pathogen fungus that lives on the ground and does not form spores. The fungus needs oxygen and 25° - 30°C temperatures to grow and can hardly grow in cool conditions. The fungus can survive in the soil for many years.

Symptoms: The leaf base is attacked first and turns yellow and then brown (rotting of leaf base). The stems rot and collapse. White fungi and tiny spherical orange blotches can be observed on the stems and growing media.

A warm and moist growing medium is ideal for the fungus to grow and multiply. 



Sclerotium attacks mostly Cymbidiums and Paphiopedilums.

Good air circulation and better watering practices will eliminate the problem.

PS: Crown Rot is a different disease caused by a different fungus.