Causes

• Inadequate light, slow-draining or flooded soil, or irrigation that keeps leaves wet leads to fungal problems on dusty miller plants. If aphids are present, they secrete a honeydew that turns white to black because of powdery mildew. Wetness and high humidity leads to fungal wilt infestation seen as black leaves and stems.
  
  

Prevention/Solution

• Examine the dusty miller plants and surroundings. Reduce irrigation to keep the soil drier and clip back any encroaching plants that block sunlight or impede air circulation. Consider relocating dusty miller plants from soggy soils or where they were receiving less than six hours of direct sunlight daily.
  
  

Considerations

• You can trim away dried lower leaves and black fungus-covered leaves with your fingers or cutting blade. This may improve air flow around the plant to improve soil drying and diminish the fungal problem. If humidity is low, prune stems in spring or summer to rejuvenate plants.