VOA慢速英语 2008 0219a

This is the VOA Special English Agriculture Report.

Back in the year two thousand, big producers of poplar trees in the American Pacific Northwest needed help. Their hybrid¹ poplars, nearly ten years old, were under threat. Young insects were getting into the heartwood, weakening a tree and making it likely to break and fall. Small, newly planted trees were being killed.

Two professors from Washington State University discovered that the threat was not from traditional poplar pests but from a new one.

Doug Walsh and John Brown found ninety-five western poplar clearwing moths³ in traps in a four-week period in two thousand one. Then, during a four-week period in two thousand two, they found more than eighteen thousand moths in traps placed in the same locations.

Unlike most moths, this one is active during the day. As a defense⁴, it can make itself look like a yellow jacket.

It was a threat to fourteen thousand hectares of poplar planted in eastern Washington state and Oregon. The producers used twenty thousand kilograms of a pesticide⁵, Lorsban, in two thousand two to try to control the outbreak. But that and other poisons failed to stop the moths.

So the professors asked for help from an expert at the University of California, Riverside. Years earlier, Jocelyn Millar had copied the sex pheromone of the clearwing moth².

Pheromones produce chemical signals that animals and insects use to identify friends and enemies. Pheromones also attract the opposite sex. The Washington State team had used Jocelyn Millar's version of the pheromone in the traps.  

The researchers began treating poplars with the synthetic⁶ pheromone in two thousand three. The idea was to confuse male moths. They would sense the presence of females and not be able to find them, and that would interfere⁷ with reproduction.

After the success of tests, and improvements to the treatment, it won full approval from the United States Environmental Protection Agency. That was in two thousand six.

Professor Brown says the synthetic pheromone is safe so workers can re-enter a forest after a few hours. And only small amounts are needed -- as little as one gram per two and a half hectares. Professor Walsh says the treatment reduces clearwing moth populations quickly. Today, the population is under control, but preventive treatments continue.

And that's the VOA Special English Agriculture Report, written by Jerilyn Watson.

 

1 hybrid   

n.(动，植）杂种，混合物

参考例句：

• That is a hybrid perpetual rose.那是一株杂交的四季开花的蔷薇。
• The hybrid was tall,handsome,and intelligent.那混血儿高大、英俊、又聪明。

2 moth   

n.蛾，蛀虫

参考例句：

• A moth was fluttering round the lamp.有一只蛾子扑打着翅膀绕着灯飞。
• The sweater is moth-eaten.毛衣让蛀虫咬坏了。

3 moths   

n.蛾( moth的名词复数 )

参考例句：

• The moths have eaten holes in my wool coat. 蛀虫将我的羊毛衫蛀蚀了几个小洞。 来自《简明英汉词典》
• The moths tapped and blurred at the window screen. 飞蛾在窗帘上跳来跳去，弄上了许多污点。 来自《现代英汉综合大词典》

4 defense   

n.防御，保卫；[pl.]防务工事；辩护，答辩

参考例句：

• The accused has the right to defense.被告人有权获得辩护。
• The war has impacted the area with military and defense workers.战争使那个地区挤满了军队和防御工程人员。

5 pesticide   

n.杀虫剂，农药

参考例句：

• The pesticide was spread over the vegetable plot.菜田里撒上了农药。
• This pesticide is diluted with water and applied directly to the fields.这种杀虫剂用水稀释后直接施用在田里。

6 synthetic   

adj.合成的，人工的；综合的；n.人工制品

参考例句：

• We felt the salesman's synthetic friendliness.我们感觉到那位销售员的虚情假意。
• It's a synthetic diamond.这是人造钻石。

7 interfere   

v.(in)干涉，干预；(with)妨碍，打扰

参考例句：

• If we interfere, it may do more harm than good.如果我们干预的话，可能弊多利少。
• When others interfere in the affair,it always makes troubles. 别人一卷入这一事件，棘手的事情就来了。