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Managing Impatiens Downy Mildew

April 10, 2012

You have no doubt heard the dire warnings about this disease reported in trade journals and from concerned growers and landscape professionals.  Here are some key facts and tips for keeping your Impatiens greenhouse crop & outdoor plantings clean and thriving this spring and summer.

  1. Impatiens downy mildew, like all disease organisms, is best prevented, not cured.  Be vigilant, be thorough, and be consistent with your production and maintenance practices and you will be successful.
  2. Impatiens downy mildew is specific to Impatiens walleriana and inter-related hybrid varieties.  Seed and vegetative Impatiens walleriana varieties are susceptible to infection.  This disease is not new and does not have any other important plant hosts other than Impatiens walleriana.
  3. It is important to start with clean plants, cuttings or plugs. There is no evidence that downy mildew diseases are transmitted by seed, so seed grown sources should initially be free of any disease.  Vigilant inspection of purchased plugs, cuttings and transplants is vital.  Growers should clean up production areas between crops.  Use an effective surface disinfectant like Green-Shield® disinfectant & algecide to start clean and stay clean.
  4. Employ a routine scouting program.  If you suspect an infection, isolate or destroy those plants immediately.  Impatiens downy mildew on infected plants can be found on the undersides of leaves.  The fungal mycelium looks like a whitish, gray powder.
  5. Use effective, preventive fungicides.  The operative word here is preventive - start with clean plants and keep them clean with preventive, timely fungicide applications.
  6. Stature® SC fungicide and Pageant® Intrinsic™ brand fungicide have both been tested on Impatiens downy mildew and found to provide excellent disease protection on greenhouse grown Impatiens.  In addition to greenhouse grown Impatiens, Pageant can also be used on Impatiens in landscape plantings. (Stature SC is only labelled for use in greenhouse and nursery uses.)  Please read and follow all label instructions.

BASF provides growers with effective tools for managing disease control and plant health.  Please contact a BASF technical specialist to help you with all of your plant protection needs.


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