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.