[00:09.87]44) Edward Knipling
[00:15.52]A leading American research scientist died last month at his home in Virginia.
[00:22.88]Edward Knipling was ninety-one years old.
[00:26.75]Mister Knipling was a world famous expert in the study of insects.
[00:32.89]Most of his work was done for the Agricultural Research Service,
[00:38.30]the chief research agency of the United States Department of Agriculture.
[00:44.15]During his lifetime, Mister Knipling received many awards,
[00:49.97]including the National Medal of Science and the World Food Prize.
[00:55.38]Last year, Progressive Farmer magazine named him among twenty-one scientists
[01:03.06]who most influenced American agriculture in the past one hundred years.
[01:08.44]Mr Knipling developed effective ways to control insects without using harmful chemicals.
[01:17.43]His efforts resulted in the disappearance of the wild screwworm population from North America.
[01:25.26]This has helped to prevent hundreds of millions of dollars in losses to farmers around the world.
[01:32.79]The screwworm fly lays its eggs in cuts in the skin of cows and other farm animals.
[01:41.75]When the young insects are born, they feed on the living tissue of the animals and cause serious wounds.
[01:50.63]Unless treated, an adult cow can die within a few days.
[01:56.09]Mr Knipling and another American researcher, Raymond Bushland, developed a method to stop the spread of the insects.
[02:07.40]They used radiation to make male screwworm flies unable to reproduce.
[02:14.69]Then they released the treated males to mate in the wild with fertile female flies.
[02:22.45]The eggs from the females could not become fertilized and did not produce young screwworm flies.
[02:31.85]As a result, the number of the insects dropped sharply.
[02:37.34]This method is now used worldwide to kill other insects harmful to agriculture,such as Mediterranean fruit flies.
[02:48.33]In Africa, the method is used to control the tsetse fly, which spreads sleeping sickness.
[02:56.07]Mr Knipling also helped develop the idea of using some kinds of insect enemies to control harmful insect populations.
[03:07.79]Some harmful insects are more easily treated with biological controls than with chemical ones.
[03:16.23]This idea has grown to include other methods that do not harm the environment |