18 AUGUST 1967, Page 21

Pest buy


A few years ago the Shell Chemical Company published an ldentikit of wild flowers and plants under the title Farm Weeds. It is a beautiful little book, illustrated with water- colours by Doris R. Thompson, showing the charms of the wild pansy, the cornflower and the dog daisy. But it is a rogues' gallery, inten- ded to give the farmer instant recognition of these villainous trespassers 'so that he can determine the most effective type of control and rate of application....' Note that applica- tion bit in the introduction. Not surprisingly Shell were thinking of chemicals, because that is what they sell. And few farmers have time to spare for more subtle forms of control that depend on an extensive knowledge of biology.

But since Smarden, when a whole farming area of Kent was poisoned by fluoroacetamide, a few students and commentators have been taking an active interest in non-chemical pest control, partly to achieve some protection for our wildlife, which is vanishing at a great rate (Shell publish a T4.4,44.,444y 44 the Countryside, incidentally), partly to protect humanity. Biological research, however, is miles behind chemistry in this respect. And the main reason is the enormous research funds at thedisposal of chemists and the almost complete absence of comparable funds for biologists. The science of selective killing that has developed over the past decade has shown us little or nothing about the long-term side effects of human ingestion of, for example, the organochlorine pesticides. A Ministry of Agriculture advisory committee, reporting in 1964, was inconclusive in its com- ments on the retention of DDT, dieldrin and others in human body fat (they are retained but what harm do they do?), but cases have been reported of illness apparently caused by DDT release from body fat. The Ministry of Agriculture committee, under Sir James Cook, did urge that fertilisers and sheep dips should no longer contain dieldrin, but gave DDT a clear field, subject to review after three years. This review is taking place now and it will be more than interesting to hear about its findings.

In a new book, Pesticides and Pollution (Collins 30s), to be published next week, Ken- neth Mellanby of the Nature Conservancy says

aldrin and heptachlor . . . have been proved dangerous and the recommendation that their use be restricted was justified. I per- sonally believe that they should be removed from use as soon as substitutes as effective, but less persistent, have been found.' The organo- chlorine compounds, says Mellanby, have pol- luted the whole world, and there is not a field in Britain 'which does not contain a detectable amount of pesticide.' These substances linger for ten years or more, and their ecological and genetic effects can spread throughout the biological chain to man and his food animals.

The curious aspect of it all is the simplicity with which such pesticides as DDT were greeted. But as Barry Commoner pointed out in Science and Survival, no one realised at first that DDT could kill a lot more creatures than insects. It is particularly lethal to fish, for example, but that was discovered only the hard way when a mili- tary beach had been sprayed against flies and was covered days later by tons of dead and rotting fish. Obviously we cannot give up the use of pesticides, but are we thinking hard enough about the alternatives?

I would like to believe that the message of George Ordish's new book, appropriately pub- lished in summer when the British city dweller takes his annual look at the countryside, was being taken to heart in official circles. He says that such devices as the introduction of a predator such as cactoblastis cactorum, which rid fifty million acres of Queensland of prickly pear in the 1920s, is both cheaper and safer than the indiscriminate use of destructive chemicals, the spectrum of which may be thought to be narrow and then prove to be wide. Biological Methods in Crop Pest Control (Coq-.. stable 30s) is not an inspiring title for a book lit with inspiration. It ought to move one of the great Foundations to support research into biological control.

Another book that opens up the wonders of symbiosis as a means of controlling weeds and pests, as well as encouraging beneficial insects and plants, is Companion Plants by Helen Philbrick and Richard B. Gregg (Stuart and Watkins, 15s). Its philosophy is biodynamism, a new name for the control of organisms by studying their mutual influences. The stinging nettle, so often looked upon as a noxious weed, assists the growth of tomatoes and improves the development of other neighbouring crops such as sage, mint and marjoram. Salsify plants among carrots will prevent carrot fly. Garlic and onions will benefit the growth of roses, while boxwood will harm them. The authors. -.fly that there is a lot more to be learnt than their little book encompasses. I believe them, and can only hope that such constructive effort will be followed up widely lest Silent Spring comes true.