【沪江慢速VOA】2月26日: 美国白蜡树面临虫灾威胁(1)
Insect Threatens Ash Trees in US (1/2)
A beetle invasion in the United States has killed at least 20 million ash trees. The invasion of the emerald ash borer was first discovered near Detroit, Michigan, in 2002. Experts believe the small green insects arrived in the 1990 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.
