How can I control powdery mildew on my garden phlox?


How can I control powdery mildew on my garden phlox?


Powdery mildew is a common disease of garden phlox (Phlox paniculata).  The fungal disease produces a grayish white coating on the leaves.  Infected leaves eventually turn yellow and then brown.  Initial symptoms appear on the lower leaves with the disease progressing upward. 

Powdery mildew is most commonly found on plants growing in shady areas and in crowded plantings with poor air circulation.  Optimal conditions for powdery mildew are cool nights followed by warm days. 

Cultural practices can reduce the severity of powdery mildew on garden phlox.  The amount of disease inoculum can be reduced by cutting off and removing diseased plant debris in fall.  Plants growing in shady locations should be moved to a sunny site.  In overcrowded plantings, improve air circulation by digging and dividing perennials. 

While cultural practices are helpful, fungicides may be necessary to control powdery mildew on garden phlox.  To be effective, fungicides should be applied at the first sign of the disease and repeated on a regular basis. 

Selecting and planting of powdery mildew resistant varieties is one of the best ways to reduce issues with powdery mildew.  The following cultivars possess good resistance to powdery mildew:

  • 'Candy Floss' (coral pink)
  • 'Sherbert Cocktail' (soft pink, greenish yellow)
  • 'Flower Power' (white with pink blush)
  • ‘Shortwood’ (rosy pink)
  • 'Swirly Burly' (lavender with magenta eye)
  • 'Wendy House' (bright red purple)
  • 'Bartwelve' Pink Flame™ (salmon pink with dark eye)
  • 'Frosted Elegance' (pale pink with dark eye)
  • 'Lichtspel' (pink with red eye)
  • 'Natural Feelings' (rosy pink)
  • 'Peppermint Twist' (pink and white)

(The resistance or susceptibility of garden phlox varieties to powdery mildew varies within the United States.  A variety that possesses good resistance to powdery mildew in the Midwest may be susceptible to powdery mildew in other regions of the country.) 

Additional Resources

A Comparative Study of Phlox paniculata Culitvars

Last updated on
June 9, 2023