Powdery Mildew
- Plant Fungal Disease
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Powdery Mildew on a marrow leaf
picture used permission of Pollinator - published
under GNU Free Documentation License,
Version 1.2

Powdery Mildew on grass
picture used permission of
Forestryimages - Clemson University - published under Creative
Commons Attribution 3.0 License
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Signs - White powdery
mould appears on the leaves, stems and buds. Young growth in particular
is affected. The disease is encouraged by the plant being dry at the
roots with damp stagnant air around the top.
Damage - Looks unsightly
and causes leaves to drop early. If the plant is well established this
is a relatively harmless disease. However, care should be taken with
younger plants since these may be drastically weakened.
Treatment - A fungal disease
so one of the best ways of dealing with it is by good hygiene. Remove
all dead leaves in autumn to prevent the spores from over wintering,
burn the leaves or take them to the skip rather than use them for compost
or you may well just perpetuate the problem.
Like many fungal diseases, this is caused by any one
of a whole group of fungi.
Mulch well in spring and autumn with well rotted
farmyard manure to prevent the roots drying out. If possible, prune
plants so they have an open shape and air can move through the branches.
Horsetail tea. Horsetail (Equisetum arvense) is a
pernicious weed which spreads by underground stems that go very
deep and form horizontal rhizome systems. This makes it particularly
difficult to control particularly on heavy soils where trying to
pull it up just breaks off the stems leaving a piece in the soil
to carry on. If you have a horsetail problem, there's a bright
side to it because an infusion of the weed makes a good fungicide
for control of mildew on strawberries and other crops, and
checks rust on celery and celeriac.
Collect the horsetail, foliage, stems, rhizomes and all,
and for each 28g (1oz) pour on 1.1 Litres (2pt) hot, not boiling,
water, and allow to stand for twenty-four hours. Strain off
the 'tea' and use undiluted.
Elder spray. This kills aphids, small
caterpillars and is useful as a fungicide for mildew and blackspot
on roses. The toxic agent is hydro-cyanic acid, so in preparing
the spray use an old saucepan.
Gather 450g (1 lb) leaves and young stems of elder prefer-ably
in spring when the sap is rising. Place in the saucepan and
add 3.3 litres (6pt) water. Boil for half an hour, topping up
as necessary. Strain through old tights and use the liquid cold
and undiluted. It will keep for three months if bottled tightly
while still hot.
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Chemical
fungicides
  Make sure you shake the bottle well before
use as the active ingredients often settle to the bottom - take it from me
I learned the hard way!
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