Powdery Mildew of Rose

Powdery mildew is a widespread disease of roses. The disease is easily recognized by the white powdery appearance of infected leaves, twigs, and flower buds. Infected leaves may also appear distorted and fall from the plant.

Powdery mildew is favored when rainfall is low or absent, temperatures are between 70 and 80, nighttime relative humidity is high, and daytime relative humidity is low. Mildew spores can spread easily by wind to nearby healthy plants.

To control powdery mildew:

  • Select powdery mildew resistant roses for planting.
  • Do not crowd plants.
  • Plant roses in full sunlight.
  • Prune infected canes and rake and discard mildewed leaves and flowers during and after the growing season.
  • Adequately fertilize roses to maintain plant vigor, but avoid excess fertilization.
  • Apply a labeled fungicide (many are available at garden centers) at the first sign of mildew. Follow label instructions for rates and timing.

This article originally appeared in the July 14, 1995 issue, p. 104.

Category: 
Authors: 

Links to this article are strongly encouraged, and this article may be republished without further permission if published as written and if credit is given to the author, Horticulture and Home Pest News, and Iowa State University Extension and Outreach. If this article is to be used in any other manner, permission from the author is required. This article was originally published on July 14, 1995. The information contained within may not be the most current and accurate depending on when it is accessed.