Two fungi cause this problem one is Sclerotinia sclerotiorum and the other is Pellicularia rolfsii. Root rots cause root system decay. Avoid soils known to be infested with Pellicularia filamentosa or Pythium mamillatum. Cucumber mosaic virus causes leaf mottling and stunted plants that fail to flower. Destroy infected plants and control the insects which carry the disease.
Powdery mildew causes a white coating on the leaves.
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