Chemical sprays will upset the ecological balance in your garden and result in a cascade of further problems. Beneficial predators will also be wiped out so that pests previously under control may take over. Instead, try one of the organically acceptable sprays, which include garlic spray, wormwood spray, pepper spray, pyrethrum spray, and the fungicides lime Sulphur and Bordeaux mixture. The latter contains copper and hydrated lime and is used on potato blight and other fungal problems. Bordeaux spray should be restricted in use as it builds up levels of copper in the soil. And lime sulphur should only be applied when a plant is dormant.
Pyrethrum is derived from the white flower heads of an African daisy species and is useful against aphids including greenfly and whitefly. But note that pyrethrum can also kill useful insects. Soapy water spray made from soft soap (not detergent) is useful against aphids.
Insect repelling ‘teas’
‘Teas’ can be made with plant material known to be insect repellent. Chop the leaves roughly, cover with water in an enamel saucepan and simmer for 15 minutes. Strained and cooled, the resulting tea can be used as a spray. Try eucalyptus, wormwood, southernwood, black sage (Salvia mellifera) and equisetum. Ensure no one is tempted to drink these teas, and that they are will labelled.
Homemade organic sprays
A number of old-fashioned homemade sprays are remarkably effective in helping to restore balance in the garden when a pest reaches the nuisance level. While these sprays may temporarily clear the kitchen with their odour, they certainly won’t endanger you or your family.
100 g (3 ½ oz.) Picrasma quassioides wood chips
3.5 litres (3 ½ qt) water
Very gently simmer the chips in the water for 2 hours. Strain and cool. Dilute the tea c1:5 with water for spraying g pests.
This makes a good all-purpose spray. The garlic works on sucking insects such as aphids on roses, while the chilli works on chewing insects such as caterpillars.
1 bulb garlic, broken into cloves
250 ml (9 fl oz./1 cup) water
3 chilli pepper pods
1 tablespoon soft soap or grated soap flakes
Place all ingredients except the soft soap in a blender. Filter through a double layer of cloth or coffee filter paper.
To use, dilute the liquid with 3.75 litres (8 ¼ pt.) of water and add the soft soap. Apply with a clean spray gun.
155g (5 ½ oz.) roughly chopped onions
250 ml (9ft oz./1 cup) water
5 feverfew leaves (for extra impact)
Prepare, dilute and use as for the Garlic spray