美国白蜡树面临虫灾威胁(2)

英语自学网

虫虫入侵，美国白蜡树们该如何抵挡？有没有谁来帮帮它们呢？The United States Department of Agriculture is working to save the ash tree. So are agriculture departments and university extensions in a number of states.
In some places, farmers are using "detection trees." These have an area where bark has been cut away. The area circles the tree and is called a…