White mould can occur anywhere on the stem, causing a characteristic bleaching, above which the area wilts and dies.  During cool, damp conditions a white fungal growth appears on the lesions.  Black sclerotia on or within the stem are diagnostic.  Phytophthora infections cause stem lesions that initially appear dark green and water soaked, then later become dry and dark purplish-brown.  All or part of the plant may wilt.