Thursday, 17 March 2016

Insecticides and the Balance of Nature

"The Ladybug wears no disguises.
She is just what she advertises.
A speckled spectacle of spring,
A fashion statement on the wing....
A miniature orange kite.
A tiny dot-to-dot delight."
(J. Patrick Lewis)

Although the pesticide found in water supplies was an anti-fungal, the use of other pesticides against insects is still widespread.

So here is an article from “The Pilot” (the magazine for Anglican Churches in Jersey), which warns about the dangers of those sprays which destroy insects. The message still needs to be heard, for insecticides are still in use, despite the warnings here.

This article, by the way, was written in 1976, which just goes to show that these environmental concerns have been present for a very long time.

Insecticides and the Balance of Nature
By Roger Harris, Fellow of the Royal Entomological Society

For centuries note, gardeners have fought a long and hard battle against that pest with a thousand mouths - the aphid - better known to vegetable growers as blackfly, to rose lovers as greenfly, or to greenhouse owners as whitefly. These three belong to a very large group of insects related to bugs.

In the days of the past gardeners tackled these pests by a long and laborious process of crushing them with their fingers, or perhaps spraying them with a solution of soapy water mixed with the liquid from boiled rhubarb leaves. No need for such trouble nowadays.

Every garden shop sells ready mixed sprays in aerosol form and systemic insecticides which can be watered into the soil around the plant.

These systemic insecticides are taken up through the roots of the plant itself, which then becomes entirely poisonous to those who suck its sap or eat its leaves.

When we treat our greenhouse, spray our roses, or water poisons around our cabbages, we are completely ignoring the possibility that we might be harming other things too, that indirectly we might be helping the very beasts we wish to destroy. No type of animal is an island, entire of itself.

Aphids have existed on this Earth for many millions of years, and during this time have become tangled in a very complex web of relationships with other animals and plants around them. Long before man came onto the scene the number of aphids was kept in careful check by an army of small insects, including ladybirds, who always managed to eat enough of them to keep the aphid hordes under control.

When our modern gardener finds some blackfly on his beans and some greenfly on his roses, he sprays the beans and waters the soil beneath the roses with systemic insecticide.

Soon the healthy and active aphids are reduced to little stumbling bags of poison, which easily fall prey to any hungry ladybirds or other aphid eaters in the area. Now most of these insecticides are non-selective, that is they are deadly to all and sundry who devour them.

And so they not only poison the aphid but ladybirds are poisoned too, and so are the many other creatures which chance to feed on the poisoned carcases.

It is a law of nature that there are always fewer of the hunting animals than the smaller animals which they feed on. And so, in our modern garden, there is a great danger that we will poison most of the hunters which normally eat our aphids for us.

Soon, fresh supplies of aphids will invade the plants which we are protecting. The common blackfly which eats our beans and cabbages also breeds on poppies and on dock, and so reinforcements are soon at hand.

Not so the aphid feeders, the ladybirds and others. They are scarcer and they breed more slowly, and if all our neighbours are using poisons then they may not be replaced at all. We will have killed the aphid's natural enemies.

The blackfly, and all his relatives, may start to romp uncontrolled over the docks in the hedgerow. They will breed rapidly, and amongst their offspring there may be some which are immune to the poisons we use. We will be much worse off than we were when we started.

Now you see why I spray the aphids in my garden with soap solution mixed with the liquid from boiled rhubarb leaves, and crush them off the plants with a pair of old rubber gloves.

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