Imaptiens Downy Mildew

Impatiens Downy Mildew is a deadly fungal disease which thrives in moist, humid conditions. It specifically infects Impatiens walleriana and hybrids, bedding Impatiens (6 pack style), Rosebud Impatiens, Butterfly and Fusion Impatiens.

The fungus can get into your garden from infected plant material, spores spread by rain or overhead irrigation, or windblown spores from infestations nearby.


Early signs include:

  • Light green, yellowing or stippling of leaves
  • Leaf edges curl down
  • Faint gray streaks on upper leaf surface
  • White, cotton-like patches on undersides of leaves

Advanced signs include:

  • Stunted plants
  • Leaf and flower drop, leaving bare stems (this occurs rapidly)
  • Infected stems collapse in cool, wet conditions

Monitor/Establish Threshold

The slightest presence of Impatiens Downy Mildew requires action. The spores of this disease spread by wind and water (rain and overhead irrigation), and can infect new plants overnight.

One source says the spores can spread hundreds of miles on the wind! Also if infected stems are left to rot on the soil the spores can persist in the soil for two to three years.

Once you have the disease there is no control.


The easiest way to prevent Impatiens Downy Mildew is to plant alternatives for at least three years.

If you have not had trouble with Impatiens Downy Mildew in previous years, you can also treat healthy plants with Actinovate, a biological fungicide, on a weekly basis to try and keep the fungus at bay.

Treatment - Action Options

* If you had Impatiens Downy Mildew last year do not plant Impatiens for at least three years because the spores can persist in the soil that long. Choose alternative plants. Ask about recommendations or stop by our Information desk. We’re happy to help!

* If you currently have Impatiens Downy Mildew DO NOT COMPOST INFECTED PLANTS! Seal them in a plastic bag as close to the area they were growing in as possible and put them in the garbage. DO NOT PLANT MORE IMPATIENS IN THE INFECTED AREA. They will die.

aphids control


  • Alyssum (part shade)
  • Bacopa (part shade)
  • Begonias- all types Coleus
  • Dichondra (part sun)
  • Euphorbia ‘Diamond Frost’ and ‘Breathless Blush’
  • Fuchsias
  • Heliotrope (part shade)
  • Hypoestes (Polka Dot Plant)
  • Lobelia (part shade)
  • New Guinea Impatiens (a resistant species)
  • Strobilanthes
  • Sweet Potato Vine
  • Torenia (Wishbone Flower)

Impatiens Downy Mildew

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Garden Pests

The Best Practices approach, sometimes called Integrated Pest Management (IPM) is an environmentally sensitive approach to dealing with garden pests. Printable pdfs can be found on each page.