UMN and MTGF Virtual Field Day 2013, Impatiens Downy Mildew

Michelle Grabowski
Michelle Grabowski

Extension Educator

Horticulture/Plant Pathology

[email protected]




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Did you know?

Impatiens downy mildew appears to be here to stay. Learn how to identify and manage this new disease of impatiens.

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Impatiens Downy Mildew

Impatiens downy mildew, caused by the water mold Plasmopara obducens, was first reported in Minnesota in 2011. For three straight summers now, impatiens downy mildew has severely disfigured impatiens in landscape beds across Minnesota. Unfortunately, it appears as if impatiens downy mildew is here to stay. What was once a sporadic problem found in isolated incidences has now become a regular occurrence in gardens across the state. Landscape managers with responsibility for annual flower beds should familiarize themselves with the signs, symptoms and management of this disease.

Action Items

  • Learn how to identify impatiens downy mildew.
  • Purchase disease free plants.
  • Monitor for disease and remove infected plants immediately.
  • Do not plant Impatiens walleriana in beds with a history of downy mildew.
  • Fungicides can be used to protect healthy impatiens from downy mildew but are not effective on plants already infected with the disease.

Additional Resources

Managing Impatiens Downy Mildew in the Landscape

Managing Impatiens Downy Mildew in Greenhouses, Nurseries and Garden Centers

What’s wrong with my plant? Online diagnostic tool