Sclerotinia Head Rot and Wilt

• Sclerotinia head rot and sunflower wilt are common diseases of sunflowers. Several species of Sclerotinia fungi -- the pathogens of these diseases -- overwinter in soil and leaf debris underneath sunflowers and other host plants. These diseases are difficult to manage since they both persist independent of weather conditions and because Sclerotinia fungal species can survive in any soils that are fertile enough to support sunflower growth.
  
  

Symptoms

• Detection of early symptoms is one of the keys to protecting your sunflowers from these diseases If a sunflower breaks out in visible mold growth, the disease or diseases have already progressed to advanced stages. The difficulty, however, is that many of the symptoms occur on the internal vasculature of the plant and are difficult to recognize on the outside of the plant. Sunflower wilt causes cankers near the base of the plant that eventually cause different parts of the plant to rot. Sunflower head rot will wilt only tissue that is already dead or decaying, but the fungus quickly begins feeding on healthy tissue as well, so wilting can spread across your sunflower in a short period of time.
  
  

Treatment Approaches

• Control methods should begin with selecting cultivars of sunflower that are resistant to these diseases. Keeping your sunflower in good health is also an important preventive measure. As noted, sunflower head rot primarily attacks dead tissue first, so keeping your sunflower free of dead tissue through cultural management and pruning will starve the fungi of any edible tissue. Sunflower wilt does attack healthy tissue, but keeping the sunflower in good health and vigor will help it naturally resist the disease before it can take hold.
  
  

Chemical Controls

• Though both of these diseases are transmitted by fungi, no chemical fungicides are currently labeled for control of sunflower wilt and head rot diseases. There are some fungicides approved for removal for cosmetic reasons of the white fungus that breaks out on sunflowers, but these fungicides are expensive; moreover, they only treat the mold growth itself and not the condition causing the mold growth, so repeated applications are necessary until the diseases causing the mold are eliminated. Instead, control these diseases through cultivar selection and cultural management practices.