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Impatiens Downy Mildew

News
04.05.2011

Please be advised that Impatiens Downy Mildew has been found within a number of UK locations this season.

   

It should be noted that Impatiens walleriana crops need to be routinely checked and a rotational fungicide programme is advisable on all Impatiens walleriana crops as the risk of infection this season is evidently high.

FloriPro Services™ protect their Impatiens walleriana using the following products:

  • Seed raised impatiens – Metalaxyl (Ridomil gold) as a sprench prior to shipment. Protection lasts around 14 days.
  • Cutting raised impatiens – Previcur (propamocarb) and Topsin after sticking. Daconil and Ridomil used 2-3 weeks after sticking.
  • Treatments last up to a week with repetition being key.
  • No treatments against Downy Mildew are made on Impatiens New Guinea as up to this point the Downy Mildew has not been seen to be an issue on this crop.

Action points to note:

  • Inspect both cutting and seed raised impatiens for the disease at regular intervals. Yellowing of the leaves, stunting and mottling are possible early signs of infection, white spores develop under the leaf as the disease progresses.
  • Remove and destroy infected plants immediately. Disinfect affected area and materials.
  • Poor nutrition, high humidity and lower temperatures will encourage the disease.
  • Cross contamination must be avoided at all times, spores can be transferred very easily by physical contact from humans.
  • Good hygiene is essential, grow on in cleaned and disinfected greenhouses and clean down areas thoroughly between crops.
  • Ventilate glasshouses as far as practicable.
  • Check any wild Impatiens (balsam) near to glasshouses for the disease.
  • Only irrigate from overhead when the leaves will dry quickly.
  • Routine preventative crop protection spraying.
  • Trial fungicides you are considering on small areas before wide spread use.

Please ask your fungicide supplier for up to date advice and view the below suggested websites for further information:

www.hortweek.com
www.adas.co.uk
www.hdc.org.uk
www.fera.defra.gov.uk

For more information and advice on Impatiens Downy Mildew please see the HDC factsheet.