Disease problems occurring in a field may be very obvious or not be detected even to a watchful eye. Weather conditions greatly affect disease potential and inoculum levels in the environment. Wet, cool years harbor different pathogens of sunflower than hot, humid conditions. Sclerotinia wilt, Sclerotinia head rot, Phomopsis stem canker, rust, and downy mildew are the five worst diseases that producers encounter. When sunflower roots come in contact with sclerotia, they germinate, infecting and decaying the roots.
Infection moves up the roots and into the lower stem, causing the plant to wilt and die rapidly.
Surviving plants are smaller than healthy plants and may or may not produce seed. Symptoms are sudden wilting of the leaves, root rot, stem canker, and production of sclerotia in the stem. Infection and death of neighboring plants occurs when diseased roots come in contact with healthy ones. Plants lodge during high winds. Refer to the head rot section for management recommendations.