GrowingSouthwark's Blog

Natural pest control
May 17, 2010, 3:12 pm
Filed under: Uncategorized
collated by a lady at my allotments I thought I would pass this on to you.

Sprays (organic) for pest control

note: under UK and EC law is is illegal to use any preparation as a
pesticide that is not approved for such use. The information here is
for historical reference only and does not imply a recommendation for
use. If you disregard this warning and make any of the preparations you
do so entirely at your own risk.

Update 22 June 2008

A few years back there was news that a German research group had found
that milk diluted with water made a good fungicide. There were various
suggestions about the ratio some said 1 pint of milk to 8 pints of
water (1:8) while others advised 1 pint milk to 4 pints water (1:4). I
recently had some mildew on the main onion crop and used the 1:4
dilution (plus a very small amount of approved liquid detergent wetting
agent) to spray the soil as a nutrient additive. Unfortunately, because
the onions were quite closely spaced, a lot of the spray went on the
leaves of the onions and cured the mildew problem!

The information below is from “Organic Gardening” by Roy Lacey,
published by David & Charles, London, 1988, now out of print.


The insecticidal properties of ordinary soapy water should be more
widely known because it would undoubtedly save inorganic gardeners a
small fortune in poisonous sprays and save many helpful insects into
the bargain.

I’ve used nothing but soapy water as a spray on my roses for many
years and have never had more than minor trouble with aphids. Soft
soap, a pharmaceutical product used as a liquid in enemas, is a very
safe and very effective insecticide to control brassica whitefly and
cabbage white caterpillars. Dissolve 56g (20z) in 4.5 litres (1 gal)
hot water and use diluted when cool enough. Soft soap can be bought
from Garden Organic

Savona insecticidal soap is a relatively new product for the control
of aphids, whitefly, red spider mite and scale insects. It is perfectly
safe to human beings, mammals, bees, ladybirds and other predators and
is recommended for use in greenhouses before the introduction of
biological controls if there are high pest levels. It is diluted with
fifty parts of rain-water and is now widely available from garden shops.

Do NOT use washing up liquid as it contains many other chemicals which can damage


There are any number of recipes for home-made pesticides, many of them
handed down over the centuries (and some of doubtful efficacy).

For example, an old remedy to deter snails and slugs is to collect
as many as possible, morning and evening. Tip them into a bucket of
boiling water and let it stand for a few days until the smell becomes
fearsome, then strain off the liquid and use it to sprinkle round
vulnerable plants, such as the young growth of delphiniums, lettuce and
so on – but not on them. The remains of the slugs and snails can also
be scattered.

Bracken spray

Effective against blackfly on, for example, broad beans and runner beans but not
against cherry blackfly.

The bracken must be gathered when brown and brittle dry. Pulp the
leaves and store in paper bags until wanted. Using a graduated jar,
measure out 120cc (4fl oz) of the bracken and pour on 420cc (14fl oz)
of hot water, stir and allow to soak for twenty-four hours, strain,
then bottle into airtight jars and keep out of reach of children, of

For use as a spray, dilute 25cc (1 fl oz) to 4.5 litres (1 gal) of rainwater and
spray each day for three days.

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.

Twigs of elder, cut in the spring and placed at intervals, inverted
V-wise, over early turnip rows, are said to ward off attack by flea

Horsetail tea

Horsetail (Equisetum arvense) is a
pernicious weed which spreads by underground stems which may go down as
deep as ten feet, forming horizontal rhizome systems at intervals. This
makes it particularly difficult to control. 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 straw-berries and other
crops, and checks rust on celery and celeriac.

Collect the horsetail, foliage, stems, rhizomes and all, and for
each 28g (1 oz) pour on 1.1 Litres (2pt) hot, not boiling, water, and
allow to stand for twenty-four hours. Strain off the ‘tea’ and use

Nettle spray

Bio-dynamic gardeners and growers have a very high regard for the
common stinging nettle, using the leaves in sprays of several kinds. As
well as using nettles as an activator on the compost heap (page 27) the
organic gardener can use them as a liquid manure and as an aphicide.

Gather 224g (l/2 lb) young nettles and soak in a bucket of water for
a week. Strain and use undiluted as a control of aphids on roses and
celery leaf miner. Add the mushy nettles to the compost heap.

Rhubarb spray

The oxalic acid in rhubarb leaves is a safe control agent for aphids,
particularly those on roses. Cut 450g (1 lb) rhubarb leaves, place in
an old saucepan with 1.1 litres (2pt) water and boil for half an hour,
topping up as necessary. When cool, add 1 dsp soap flakes dissolved in
275ml (l/2 pt) warm water. This acts as the wetting agent when added to
the strained rhubarb liquid. Stir the mixture thoroughly and use
undiluted as a spray.

Soap spray

Use the recipe above as an effective weapon against aphids on many crops.

Seaweed spray

The value of seaweed as a liquid manure is well known. Used as a foliar
feed on a wide range of vegetable crops, it also has an insecticidal
and fungicidal effect possibly because the alginates make the surface
of the foliage less attractive to pests and the spores of fungi.


The advice from the book quoted above is dated. As far as I know
none of the fungicides shown below are now approved for organic use.
Never use anything containing sulphur on cucumbers, marrows, courgettes
or any other squash as it will kill the plant. A few years back I heard that
horsetail tea was once used as a fungicide.

Bordeaux mixture

This was discovered in 1845, but not used as a fungicide until 1885
when it was found to control downy mildew . It is the most important
preventative of potato blight and is made from copper sulphate and
lime. Applied before the fungus spores of blight settle on the leaves,
the copper sulphate gradually releases small amounts of soluble copper
which kills the germinating spores. It is equally effective in
preventing blight attack on tomatoes outdoors.

Burgundy mixture

Substantially the same as Bordeaux mixture, but the lime is replaced by
washing soda. It can be used as a prevention against mildew on roses
and gooseberries by spraying the bushes in January.

Potassium permanganate

A combined pesticide and fungicide that offers some control over aphids
and powdery mildew on roses, delphiniums, chrysanthemums and other


Usually sold as flowers of sulphur or yellow sulphur, it is
also available as a brand-named spray for control of black spot on
roses, powdery mildew and scab on fruit vegetables and ornamentals. It
can harm parasitic wasps and predatory mites.

Also available as a combined insecticide and fungicide when mixed
with lime. It is used as a winter wash on fruit trees and is useful in
controlling big bud and other mites.


Used neat it is an effective winter wash for soft and top fruit. For
gooseberry mildew use 0.5 litre (1 pt) urine to 3.9 litres (7 pts) hot
water into which 84g (3oz) washing soda and 28g (1 oz) soap flakes have
been dissolved. Spray when cool.

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