在2014年5月25日的托福閱讀考試中有這樣一道題：如何處理害蟲。針對這道托福考題，出國留學網(wǎng)(www.liuxue86.com)小編來為大家普及一下關于如何處理害蟲的背景知識，這樣有助于考生在面對這類題目時方便作答。小編在此提醒大家：本篇文章講解了處理害蟲的不同方法。理解文章時按照不同的處理方法梳理文章的結構，不同的方法要把握住作者關于其優(yōu)點和缺點的介紹，不同的方法的不同特點為文章出題的題點。
托福閱讀真題再現(xiàn)：
講得是pest的問題，如何處理害蟲。。
先講了一個例子好像是美國西南部，具體記不清了，其實是為了引出 chemical 方法 ，就是殺蟲劑pesticide，而且還講了殺蟲劑的負作用，會對native的一些物種造成預想不到的損傷。同時pest產(chǎn)生耐藥性的時間大約5年，遠短于研制出新的pesticide所需要的時間。(就是說這方法有明顯缺陷，好引出下面的方法，你們懂得!!!肯定有題的嘛...)
然后就講了biological方法，引進pest的天敵，因為多數(shù)頑固的pest其實是外來物種，之所以成為pest就是沒有天敵。這里舉了中國古代的一個例子，知道例子的功能就好。 (有題)然后這提到了一些不足，細節(jié)記不太清楚了。
最后來到了終極大招，一個叫IPM的方法讓害蟲們明白!!!其實就是一種integrated的什么方法，綜合考慮各種因素，什么經(jīng)濟啊，生物學啊，如果不得不用殺蟲劑要控制劑量啊等等(有排除題)。其實我覺得不算新方法，但是就是綜合考慮，然后就有了IPM這樣一個酷炫的名字。
解析：
本篇文章講解了處理害蟲的不同方法。理解文章時按照不同的處理方法梳理文章的結構，不同的方法要把握住作者關于其優(yōu)點和缺點的介紹，不同的方法的不同特點為文章出題的題點。
Insects become resistant to chemical insecticides very rapidly—it can happen in as few as five generations. This is natural selection at work.
The problem is that an insecticide never kills all of its intended victims. If even a few insects survive, they will reproduce. These surviving insects will produce two types of young—those that are resistant to the spray, and those that are not. The non-resistant insects will be killed in the next spraying, but those that are left reproduce. At each generation, the number of naturally resistant insects in the population increases.
An individual insect does not become resistant during its lifetime. It is born either resistant or non-resistant, and it is the population as a whole that gradually becomes resistant to the pesticide over time. The Bt toxins become ineffective, and the benefits of using them (less toxicity to non-target species) disappear.
As this occurs, a new pesticide must be developed. Over time, populations of insects can become resistant to more and more pesticides. As a result, humans need to make different pesticides that are generally stronger.
Organic farmers have used Bt on their crops for a number of years. They are concerned that the increased use of the Bt toxin could speed up the development of resistant insect populations.
Entomologists know that controlled, laboratory experiments with generations of insects cannot be easily reproduced in the field. How the resistant insects breed with refuge insects, and over what time frames, will determine the success of this technology.
These concerns are balanced by concerns that existing pesticide practices can be much more dangerous for non-target insect species than insect-resistant crops. Conventional non-selective pesticides kill many non-target insects. By reducing the number of sprays needed, insect-resistant crops help to preserve beneficial predator insects and simplify management decisions.
>>>點擊了解更多托?？荚囅嚓P信息