Fatal Hormone

Scientists anxious to find a safe but powerful pesticide have long been fascinated by the juvenile hormone that is secreted by insects. At certain stages of an insect's life cycle, the hormone must be present to regulate growth and control the transformation from larva to pupa. At other times the hormone must be absent, or the insect will develop abnormally and never reach sexual maturity. If a sufficient dose is given to a mature female, it can make her sterile for life thus eliminating future generations. The trouble is that the hormone, synthesized in commercial quantities and sprayed across a field, could eliminate insects essential for pollination as well as those that destroy crops.

Czechoslovak scientists have now developed a technique for using hormone-like chemicals to attack one species of bug at a time. Working with DMF, a synthesized chemical compound that acts like a juvenile hormone, a Prague team under Biologist Karel Slama discovered that it took just one microgram (a millionth of a gram) to sterilize for life a female linden-bug. They also found that a dose as much as 10,000 times the amount of DMF required to produce sterility would cause no other harmful effects. So they figured that a male linden-bug treated with a massive quantity of DMF might be able to lead a normal life, yet pass enough of the chemical to females during mating to sterilize them.

Sterilization in All. To test their premise, the Czechs dripped solutions containing 1, 10 and 100 micrograms of DMF on three groups of ten male linden-bugs, then placed each group in a separate container with ten normal females. As the bugs mated, eggs laid by the females were carefully watched. None of those from females confined with males treated with 100 micrograms of DMF ever hatched. Few eggs from the 10-microgram group and only half from the 1-microgram group eventually hatched into larvae. Analysis of the females that had mated with the 100-microgram males proved that between 1 and 5 micrograms of the absorbed DMF had been passed to them in the male sexual fluids, enough to cause lifelong sterilization.

If the Czech-mating technique works on other insect species, it may provide a final answer to man's bug problems. Unlike the spraying of DDT and other chemical pesticides, the hormone technique affects only the treated species of insect and does not contaminate plant and animal life. And insects cannot develop immunity against it, for if they did, they would become immune to the hormone that is essential to part of their life cycle. The new technique is also superior to the release of radiation-sterilized male insects, which often fail to compete with their unradiated brothers in mating with fertile females.

Harvard Biologist Carroll Williams, once Slama's senior associate in juvenile hormone research, foresees practical applications of the Czech method "probably within five or six years." Although DMF itself affects the sterility of only a few insect species, Williams points out that other juvenile hormone-like chemicals can be used in the same way to sterilize a wide variety of insect pests. "The day may be near at hand," he says, "when we can do in individual insect pests such as the housefly, mosquito and boll weevil."

This file is automatically generated by a robot program, so reader's discretion is required.