The HDC has released a factsheet that provides specific advice on the management of the metalaxyl-M resistant downy mildew strain.
Action points are:
Where possible grow seed-rased impatiens with the exception of New Guinea impatiens, avoid the production fo cutting-raised plants.
Monitor crops carefully for signs of the disease, provide good levels of ventilation and avoid watering plants late in the day.
Apply a protectant fungicide programme to seed-raised crops during the production phase.
Dispose of infected plant material into sealed bags or bins to minimise spread of the diseases.
The disease hit the UK in 2003 before reappearing in 2007, 2008 and 2011, when a strain of impatiens downy mildew (Plasmopara obducens) was found to be resistant to metalaxyl-M.
HDC says protectants Fenomenal, Paraat and Revus currently provide some protection.
For further details see Factsheet 05/14 on HDC projects PO 011, PO 011a and PO 012