Use new plug frays, or clean and disinfect trays or pots if they have been used. Be careful not to contaminate the growing medium with dirty hands, tools, or hose nozzles. After watering, hose ends should be hung up to keep them off the floor. Keep the humidity low and maintain adequate but not excessive fertility. Avoid planting into fields with a history of Pythium or Rhizoctonia diseases.
Sclerotinia blight is caused by the fungus Sclerotinia sclerotiorum .
Sclerotinia blight is not commonly a problem in the greenhouse but because the fungus is soil-borne it is a perennial problem wherever it becomes established. The pathogen produces sclerotia inside or on the surface of lesions. They can survive for years in the soil and are responsible for initiating disease. Germination of sclerotia and initiation of disease are dependant on prevailing weather conditions. Optimum temperature for sclerotia to germinate is about 52 o F but some sclerotia germinate over a wide range of temperatures.