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Rose powdery mildew

Symptoms

Leaves and buds on roses, possibly even stems and thorns, are covered by a dusting of white powder.
Find it on: roses - other powdery mildews affect other plants
Time to act: spring, summer

Overview

Rose powdery mildew is a fungus that produces airborne spores from infected stems or buds on roses. After overwintering on your plants, the disease is most likely to flare up if the roots are in dry soil and the leaves are in humid air - conditions that are often found when plants are grown near or against a wall.
Solution
Leaves and buds on roses, possibly even stems and thorns, are covered by a dusting of white powder.
Organic
Prune out and bin (don't compost) infected leaves or stems. When buying roses, choose varieties with good resistance to powdery mildew - a reputable grower will be able to advise. Keep the soil around the roots moist at all times. When planting roses, prepare the soil well by digging in generous amounts of well-rotted compost or farmyard manure into the planting hole. For established roses, a thick layer of mulch around the base of the plant will help.
Chemical
Before symptoms appear, apply a fungicide containing flutriafol or myclobutanil at the recommended intervals from early spring.



Discuss this problem

Talkback: Rose powdery mildew
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ginger3 28/08/2013 at 09:49

my problem is not roses with white powdery mildew it is my double begonoia,s in my flowering baskets they started off great with everyone commenting about them but now thet looking milky and dry leaves even though i water them every day.

TomMcf 29/09/2014 at 10:35

WE have a number of large climbing roses against the wall of our house that seem a good 40+ years old, one of which had mildew this year and was pruned back very hard and sprayed in april, The new healthy growth is now starting to become covered again with powedery mildew, How should I deal with this, prune hard again, spray the walls, remove entirely? The neighbouring monster roses do not seemed to be affected at all, considering their close proximity! I would appreciate any advice, cheers, Tom Mc

David K 29/09/2014 at 11:05

Bit of a nightmare at this time of year, I've managed to keep mine clear with fortnightly spays of 'Roseclear'.

Liriodendron 29/09/2014 at 11:30

I think David is right.  You need to spray at the first sign of mildew and keep at it, or it will creep up on you...  Mildews are specific to the host plant so rose mildew won't spread to other plants.  And some cultivars are more susceptible than others, which might explain why only one of your roses is affected, Tom McF.

Water stress seems to be the main reason plants are affected with mildew, which is why climbing roses on walls often get it badly.  Regularity of watering is very important, and mulching to keep the moisture in can help too.  The fungus spreads most rapidly when the temperature is in the low 20s, which just about covers the average British summer...    The spores over-winter on leaf litter so clearing up and burning or binning fallen leaves around the infected plants is a must.

Ginger, hard luck with the begonias!  It's really difficult to keep hanging baskets sufficiently moist when it's a dry summer, even if you water every day - and the air circulation is often not very good, because you want your plants packed closely together to give a good display.  You could try an organic spray (I think there's one made by Vitax) if you don't fancy chemicals, though it might be too late to make them look good this year