Powdery Mildew Management in the Home Garden

Powdery mildew is a common fungal disease found in a wide range of plants, that causes cosmetic damage but would not result in plant death. Symptoms occur on the leaves as powder sugar or "fuzz". When the infection starts, distinct circular areas of white mildew are formed. As infection progress, the foliage can be covered with powdery mildew.


 


Powdery mildew is the disease name, or the generic term we use to refer to the symptoms. However, the fungi that cause powdery mildew are different for every host plant or family, meaning the powdery mildew you observed in your roses will not cause disease on trees or shrubs.


 


Powdery mildew control in the home garden after symptoms appear is challenging. Powdery mildew varieties of winter squash and pumpkins, as well as annual and perennial ornamentals, that are resistant to powdery mildew are available (see additional resources, below).


 


Planting resistant varieties is an effective way to minimize this disease in vegetables and ornamentals. Other important cultural practices include planting in full sun, increasing aeration and avoiding excess fertilizer use. Overhead irrigation is not recommended as it can contribute to the development of other diseases.  


 


For susceptible varieties, fungicides are available but are mainly protectant, not curative.  Fungicides can only help when applied prior to the infection. Fungicides available for the home garden include:


  • chlorothalonil products (such daconil or Echo)
  • biofungicide (like Serenade)
  • sulfur products (such Safer Garden Fungicide; may burn plants if label directions are not followed carefully)
  • some oil sprays

All sprays will have little to no effect if applied in late summer after symptoms appear.


The fungal pathogens that cause powdery mildew are capable of surviving the winter.  Therefore late fall sanitation is recommended to help reduce the amount of the pathogen present in the garden next year.


 


Additional Resources


 


Iowa State University


 


Other


 


 


Symptoms of powdery mildew on peony.Symptoms of powdery mildew on peony.


 

Authors: 

Lina Rodriguez Salamanca Extension Plant Pathologist and Diagnostician (Program Specialist II)

Dr. Lina Rodriguez Salamanca is an extension plant pathologist and diagnostician with the Iowa State University Plant and Insect Diagnostic Clinic, a member of the North Central Plant Diagnostic Network (NCPDN) and National Plant Diagnostic Net...

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 24, 2015. The information contained within may not be the most current and accurate depending on when it is accessed.