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？
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 1990s in shipments of goods from China. The emerald ash borer has des…