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Downsized Powdery Mildew Recipe

februarysgirlfebruarysgirl Posts: 835
in Problem solving
I had a Rosa Rugosa delivered last week and at first glance it looked OK. Then I noticed the discolouration on some of the leaves and what I assumed was powdery mildew. I chopped off the affected leaves but I haven't felt comfortable planting it in the raised bed (open bottomed). My concern is that if it's got a serious problem, I didn't want it to get too established and then be a PITA to get out (I planted a 9cm dwarf kniphofia and a year later when I tried to dig it out it the roots were horrendously large, I assume a rose would be so much worse). So, the plan was to pot it up to a 4l pot (currently in a 2l) and put that in the ground to keep watch with a view to planting it in the bed in the autumn (all being well). I've just been out and there are more specks of powdery mildew showing.



I've been looking at home remedies and a mixture of baking soda, soap and water seems to be popular however, all of the recipes are based on using a gallon of water but I don't need anywhere near that amount for a young rose in a 2l pot.  Does anyone have a recipe for a small scale treatment?

Also, I'm new to roses so have no idea what I'm doing.

Posts

  • CharlotteFCharlotteF Posts: 337
    I use potassium bicarb, not sodium bicarb, as ideally plants don't want too much sodium (whereas they can make use of the potassium). I just bought a small bag of food grade stuff on amazon. I followed the instructions here and just scaled down the amount of bicarb https://www.hpaa.org.uk/index.php/controling-pests-diseases/388-powdery-mildew

    I used 1 tsp I think as my sprayer is nowhere near a gallon! I can't tell you if it's really worked yet (I'm using it on blackspot, and olive peacock spot), but it was easy enough to make up so I'll keep trying.
  • PianoplayerPianoplayer Posts: 624
    Hi - powdery mildew generally strikes stressed plants, so you may need to up your watering significantly. That often sorts it. Definitely pot on or plant. It will be hard to keep it supplied with enough water in a small pot.
  • FairygirlFairygirl Posts: 55,117
    As @Pianoplayer says - lack of water is the usual reason. A rugosa in a small pot at this time of year will struggle to get enough water to take up. At the very least, find it a shadier spot to help reduce evaporation, and therefore the stress it causes, but getting it potted on or planted will help. 
    It's a place where beautiful isn't enough of a word....



    I live in west central Scotland - not where that photo is...
  • KiliKili Posts: 1,104
    edited July 2021
    I doubt its anything to do with watering. I have plants fed by a wicking material the plants take up water when they need it and they still get powdery mildew. Its a whole host of conditions that contribute to this condition.

    Powdery Mildew is a Fungal disease. You can play with all sorts of Internet remedies if you wish to. I would simply go and buy a Fungicide spray and treat it with that. Rose Clear is one I use for my Roses as it has a Fungicide built in. There's also another product safe for use with edible plants 

    There's some good information on the RHS website which may help you.

    'The power of accurate observation .... is commonly called cynicism by those that have not got it.

    George Bernard Shaw'

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