美国英语听力80篇3 Lesson44


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[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

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