Rhizoctonia, Pythium, Fusarium, Thielaviopsis and other soil-inhabiting fungi frequently cause serious root rots, particularly on herbaceous ornamental plants. Plants affected by these fungi may come from the nursery already infected with the fungus or may become infected after transplanting.
Plants infected with these root rotting fungi may exhibit many symptoms, including wilt and nutrient deficiencies. Check small roots for rot by gently pulling them. If roots are darkened and break easily, root rot may be the problem.
Control: The primary control is to avoid the typical urban stress problems, particularly overwatering and/or poorly drained soils.