Mildew on Roses and How to treat -
The mildew that normally affects roses, is a form of powdery
mildew. There is also a more serious - but rarer for of mildew (Downy Mildew)
which this article is not concerned with. The white powdery mildew mould
start off on the leaves and soon spreads to buds and other young rose shoots.
The affected foliage curls up and eventually falls off if not treated. Flower
buds may not open properly, and if they do, will be severely affected. As
Blackspot, Rose mildew is prevalent in dry hot conditions - in particular
when the root area is dry and lacking moisture.
It usually becomes visible in
mid/late summer and autumn. In particular, hot autumns - with dry hot days
followed by cold nights - will bring the powdery mildew disease to the
Poor air circulation is a well documented cause, and is
particularly a problem with climbing roses against a wall, or bush roses
within confined spaces.
The affected leaves and
shoots showing any sign of mildew, should be cut off and burned. Combine
this activity with a good all-round rose fertiliser feed to help establish
new healthy growth. A good mulching of rotted organic matter will help
conserve moisture at the root area.
There are several varieties that are very susceptible to rose
Mildew - among them being Frensham and Iceberg.
A preventative spraying routine can be started in early
spring, though it is normally sufficient to start spraying at first sign
of the mildew. Repeat applications of rose fungicide, or a combined
spray will then be necessary - every two weeks. Read the label.
A good organic treatment for rose mildew, is with a mixture of Baking
Powder and vegetable oil (The latter to help the baking powder to
'stick' to the rose leaves.
A light case of Powdery mildew in early summer.
Prevention is best achieved by
- Mulching around the rose root system in early spring
- Feed with a general rose fertilizer - not high in Nitrogen.
Tomato fertilizer will also be suitable.
- Grow mildew resistant Rose varieties.
- Ensure plenty of air circulation and not dense shade.
In this case, the powdery mildew has all but taken
over the rose bush and leaf drop will be inevitable. All that can be
done at this stage, is to pick off the dead leaves and destroy by
burning. Spray the remaining bush weekly - and the soil around it with
Multirose or Systhane fungicide. Keep the rose well watered and ensure
that the water soaks well into the root zone.
Far better to have 'prevented' this degree of rose
mildew by following steps above.
By David Hughes -