Background: This sunflower sample from a commercial farm in Central Florida was showing widespread, fast decline with necrosis throughout the plant.
Diagnosis: After culturing a sample of the plant tissue, we determined that the root cause of the illness was white mold (Sclerotinia sclerotiorum), which is unfortunately considered to be one of the most destructive diseases for sunflower.
Treatment: There are currently no fungicide recommendations for this pest in Florida and management is dependent on cultural controls. S. sclerotiorum survives for years in the soil so rotating away from this section of field would be a good start. Increased plant spacing and decreased nitrogen applications to reduce leaf size is another way to ensure plants dry better after rains and humid nights. You’ll also want to keep a good handle on any broadleaf weeds, as these can provide a host for S. sclerotiorum.
“Just Rolled into the Clinic” is an ongoing series of interesting issues from the commercial plant clinic at the UF/IFAS Mid-Florida Research and Education Center.