Powdery mildew systemic treatment

Pippa7

Please can you advise if there is a Powdery Mildew treatment that is not needed to be sprayed onto the leaves. 
We have a huge hedge that has PM, it is responding reasonably, in parts, to sprayed on potassium bicarbonate. The problem is that I am unable to reach large parts of the plant, as it is 3 meters high and 5 meters wide, and also reaches deep over my garden wall into the neighbours garden.
I prefer organic methods if possible, but am desperate to treat properly as it is a boundary providing privacy. 
Is there a treatment I can water on the roots?
Many grateful thanks in advance 

Dovefromabove

Powdery mildew usually affects plants that are under stress, frequently due to drought.  
I think the best treatment for your hedge is to ensure that  the soil around the roots is well watered ... hopefully you've had plenty of rain by now, but it's worth checking and possibly giving the hedge a gallon or two of water every yard or so along its length as if it's a large hedge the foliage and the wall alongside it may well have prevented much of the rain to penetrate to the root area.  Your hedge should be fine again when new spring growth appears.

In future years try to prevent the root area from drying out in dry spells. 

Hope that helps. 

  

Obelixx

I agree?  Lots of water deep down to the roots and later this autumn, after heavy rains, mulch with well-rotted manure/garden compost/grass cuttings/strulch depending on availability and budget.  It will, in time, improve the soil as the micr-organisms and worms work it in and will also help to prevent moisture loss in future dry periods.  

Mulching every autumn is a good idea if you can.  Just make sure the soil is thoroughly wet first so you don't lock in dryness.