Texas, 1961

In these instances no desirable changes appeared in the plant grown directly from treated seeds, but they appeared several generations later. In most cases hundreds of thousands of plants were examined before the desirable ones were found. The desired changes were almost always accompanied by undesirable ones, and years of cross-breeding and “purifying” were necessary to obtain usable varieties.

The technique of radiation breeding can be used on any form of life where large numbers can be grown and discarded at little cost. The output of penicillin has been increased a thousandfold by repeated mutations caused in the microorganism producing this antibiotic. Several studies on radiation breeding of poultry have been started.

An ingenious reverse twist of induced mutation is being applied in the field of plant diseases. While some scientists are irradiating seeds and plants in an effort to obtain disease-resistant mutations, others are irradiating the fungi which cause the diseases. They hope in this way to foresee the new strains of pathogenic microbes that will occur naturally in order to breed resistant plants before the new diseases appear.

Some claims have been made that radiation can stimulate plant growth, germination, earlier maturity, and so on. Similar benefits are sometimes claimed for human health. These allegations are almost never proved in reputable laboratories. It seems likely that radiation is stimulating, in the words of one authority, “only in the sense that a pruning knife is stimulating.”

Can Radiation Destroy Germs and Insects?

Food technologists have studied ways of preserving food with radiation for more than ten years. Their findings indicate that complete sterilization of food with radiation requires doses so high (2 to 6 million roentgens[2]) that cost is prohibitive at present, and the food often becomes distasteful. These amounts of energy completely destroy the microbes and enzymes which normally cause food to putrefy.

If radiation is to be used in preserving food, it will probably be as a supplement to conventional methods of heating and freezing. “Pasteurizing” with radiation to destroy most (but not all) of the microbes in meat or fruit or vegetables is accomplished with less than five per cent of the dosage required for sterilizing. Such treatment does not alter flavor or texture appreciably and could be used to prolong the refrigerated “life” of many fresh foods. It is the responsibility of the Federal Food and Drug Administration to determine that no threat to human welfare could possibly result before approving the use of high-energy radiation to preserve foods.

With agricultural products stored dry, such as grain, tobacco, and wool, the chief agents of damage are not microbes, but insects. The loss of stored field crops caused by insects is estimated at $200 million annually in the United States. Deinfesting such goods with radiation doses in the “pasteurizing” range promises to be practical and causes no apparent change in the product.

Like many other foodstuffs, potatoes are often stored for months between harvest and use. Precaution must be taken to prevent their deterioration during storage not only from decay but also from sprouting.

Cold storage inhibits sprouting but is costly and has another serious drawback. In the making of potato chips, tubers held at low temperature contain excess sugar and result in darkened chips. Storage at higher temperatures prevents conversion of starch to sugar but encourages sprouting.

Atomic energy promises to resolve this dilemma. Given low doses of gamma rays (5000 to 10,000 roentgens), potatoes may be kept at room temperature for a year or more without sprouting. Similar doses inhibit sprouting of onions. The estimated cost of irradiating tubers and bulbs at such doses is as low as 14 cents per ton. No chemical changes have yet been found in irradiated potatoes that would make them unsafe for eating. In fact, health officials in Canada have recently approved the use of gamma rays on potato tubers that will be stored and later used for human food. Our own Food and Drug Administration has given similar approval for applying gamma rays to bacon and fast electrons to wheat (for killing insects).

An ingenious application of atomic energy to agriculture concerns the screwworm fly, which inhabits large areas of southern United States, Mexico, and the Caribbean. The fly lays eggs in open wounds of livestock, including navels of newly born, and the burrowing maggots inevitably kill the animal. In the southeastern United States, damage from this insect amounted to $15 to $25 million annually.

In the years 1958 and 1959 more than two billion screwworm flies were deliberately released from airplanes over the entire state of Florida and parts of Georgia and Alabama. This astonishing act was a major step in successful eradication of the pest from southeastern United States.

The entomologists who conceived this remarkable scheme had the following information from basic studies: the insect produces a generation about every three weeks. In the pupal stage males can be sterilized by 2500 roentgens of X or gamma rays, females by 5000 roentgens. The insect can be reared in large numbers. Sterile males are fully competitive with normal males for mates. And, of course, sterile eggs do not hatch. (It was helpful, though incidental, that females mate only once.)

After initial tests on an island in the Caribbean, a large fly-producing plant was set up. Flies were grown to the pupal stage, irradiated with 8000 roentgens of gamma rays, permitted to mature, and released from airplanes. With 50 million flies being released weekly over Florida, Georgia, and Alabama, the area was smothered with sterile flies, and the number of eggs that hatched (from the normal native flies) rapidly diminished to zero. The program was continued for 18 months, and in this time the insect was completely eliminated.

Certain other insects are being considered for the sterility-eradication technique. Among them are the boll weevil, European corn borer, mosquito, and tsetse fly. Oriental scientists are using gamma rays instead of the conventional heating to kill silkworms inside cocoons.

How Does Radiation Affect Farm Animals?

At a few colleges of agriculture in this country, radiation effects on farm animals are being studied.

Although it may not be flattering to be likened to a pig or a donkey, the fact remains that human beings are physiologically very similar to swine and burros. These animals are mammals with simple stomachs and have the same general size, shape, and placement of organs as do humans. Radiation studies with swine and burros, although slow and expensive, should give information more applicable to humans than the more rapid and inexpensive studies with small laboratory animals.

What Else Can Radiation Tell Us?

Two characteristics of soils besides fertility are vitally important and difficult to measure. These characteristics are moisture and density. Moisture must be determined frequently for efficient irrigation. Density controls the pore space available for water and oxygen; the possible damage to the soil from tillage and harvesting machines is revealed by before-and-after tests of density.

Both soil moisture and density were formerly determined by laboratory methods, which had two drawbacks: the methods were laborious, and they tested