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What Do Organic Growers Do About Insecticides?
Many organic gardeners deal with pests by making up natural sprays themselves. Nettle spray for greenfly and wormwood tea for blackfly are two common examples. However there are some commercially available insecticides that are used by organic gardeners for extreme problems. While they are considered safer than many other chemicals they are not specific to pests and should only be applied in an emergency.
Derris
Derris is the best known of the so-called organic insecticides. Made from the root of a tropical plant, it is highly effective against aphids, red spider mite, caterpillars, weevils, flea beetles, apple sawfly and many similar pests. A great advantage of derris is the fact that it breaks down very quickly in the soil and is harmless to bees. However, as it was originally used to poison fish in Malaya it must not be applied anywhere near ponds, streams or rivers. It also kills the eggs and larvae of common ladybirds.
Pyrethrum
This insecticide comes from a type of chrysanthemum grown in Zimbabwe. It is mentioned in organic literature as a control for greenfly, blackfly, weevils, flea beetles and other pests.
However pyrethrum is dangerous to fish and kills ladybirds and bees. If you have to use it, then do so in the evening when the bees are not around.
Quassia
Quassia comes in the form of wood chips from a particular West Indian tree and is effective against most small flies. It is harmless to adult predators such as hoverflies and ladybirds.
Quassia is effective against most species of aphids but can destroy the larvae of hoverflies.
Soft Soap
Many organic gardening books refer to soft soap as a safe insecticide. Younger gardeners might wonder what it is. This old-fashioned green soap is not as pleasant to use in the shower as the more modern highly perfumed varieties, but the potassium carbonate which it contains is effective against most small pests including aphids. It's often recommended to be added to other sprays because of its ability to act as a 'sticker' or wetting agent. It helps the solution to stick to the plant especially the underside of leaves.
Biological control
Initally used by commercial growers, increasing numbers of biological controls are now available for gardeners. Not that the idea is anything new. Gardeners who carry ladybirds to their aphid infected plants or grow plants to attract predators have been using biological control for years.
The great advantage of using naturally occurring predators is that the predator will only attack the specific pest. Also, unlike chemical controls there is no danger of the pest developing an immunity.
They are quick and easy to apply. For example, for greenfly all you do is sprinkle a few eggs of the predator on every third or fourth plant and wait two or three days till they hatch out and begin to devour the pests.
There's no need to be afraid of these tiny predators. If, like me you are a curious individual, you can safely hatch out a few in your salad bowl and observe them at work.
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