Many crop protection chemicals are hazardous, either to people, or to the environment, or both. The hazards to the consumers of crop products are usually slight or insignificant, but they concern very large numbers of people. However, it must be noted that some pesticides act as hormone mimics, and they may be very dangerous to an unborn foetus, or a young child. The dangers are also great for the much smaller numbers of people who actually work with these chemicals. These are mainly agricultural workers, and the dangers can become serious, even acute, when safety precautions and supervision are inadequate.

The hazards to the environment are many and various. The best known dangers are the killing of non-target species. Some of these non-target species are agriculturally valuable, such as pollinating insects, and the agents of biological control. Occasionally, there is a risk of irreversible damage, when a rare species is threatened with extinction. Some animals are particularly sensitive to the presence of crop protection chemicals. For example, there is now a serious decline in the world population of frogs, and some species appear to have disappeared, probably for ever. Other species suffer from the side-effects of crop protection chemicals. For this reason, there has been a decline in the numbers of insect-eating birds. Usually, pesticide hazards are not discovered until considerable environmental damage has been done. There is then, quite rightly, a public outcry, but the difficult task of crop parasite control becomes even more difficult.

Sadly, many of these hazards are not due to the pesticide itself, so much as to its misuse. When compared to the salts of lead, mercury, arsenic, and cyanide, for example, DDT is an excellent and relatively safe insecticide, which is also incredibly cheap. Unfortunately, it was applied to agricultural crops with such abandon, and in such enormous quantities that there was serious environmental damage. Nevertheless, in my opinion, the use of DDT should have been controlled, rather than banned. Had that control been present from the outset, it is likely that many DDT-resistant insects would never have appeared, and those thin-shelled eagle eggs would never have become a problem. It must also be remembered that not all crop protection chemicals are hazardous. To the best of our knowledge, a century of use of Bordeaux mixture, and perhaps a millennium of use of natural pyrethrins and rotenone, have not harmed anyone.

One again, a comparison with horizontal resistance is illuminating. Horizontal resistance is absolutely safe, both to people and to the environment.

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