Beetles are invading ash trees in the United States and now have killed at least twenty million of them. Experts believe the small green insects arrived in the 1990s in shipments of goods from China.
The emerald ash borer has destroyed trees in the Midwest and as far east in the United States as Maryland. The insects have also spread as far north as Ontario， Canada.
Ash trees are popular. They grow well in heavy clay soils， and they can survive ice storms well. They produce many leaves， so they provide shade protection from the sun. And in the fall the leaves turn a beautiful gold and purple.
Ash trees can resist many diseases. But they cannot resist the emerald ash borer. It lays eggs on the bark. Then the young larvae drill into and feed on the inner bark. This harms the ability of the tree to transport water and nutrients.
The insect is attacking tree farms and can also spread when logs and firewood are transported.
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 girdle. The girdling process weakens the trees. It makes them easier targets for borers， and shows if the insects are nearby.
Efforts to stop the spread of the emerald ash borer include cutting down affected trees. A tree farmer in Maryland， for example， recently faced the loss of hundreds of trees.
There are worries that the ash tree might disappear unless the invasion is controlled. To prepare for such a possibility， a government laboratory is collecting seeds from ash trees.
73. Find in the passage a word closest in meaning to the underlined word “invading”。
74. According to the passage， how do the emerald ash borers destroy the trees? (回答词数不超过8个)
75. What is the purpose of collecting seeds from ash trees by a government laboratory? (回答词数不超过6个)
「答案及解析」
73. attacking.根据划线单词所在句子的语境Beetles are invading ash trees in the United States and now have killed at least twenty million of them可知，invading意为“攻击，袭击”，于是在文章的第五段The insect is attacking tree farms and can also spread when logs and firewood are transported可找到attacking一词。
74. Their larvae drill into the trees‘ inner bark. / Their larvae feed on the trees’ inner bark. 根据文章第四段最后两句Then the young larvae drill into and feed on the inner bark. This harms the ability of the tree to transport water and nutrients 可知。
75. To stop the trees‘ disappearing. 根据文章最后一段 There are worries that the ash tree might disappear unless the invasion is controlled. To prepare for such a possibility， a government laboratory is collecting seeds from ash trees可知。
