The hemlock(铁杉) trees along the Wappinger Creek, New York, look healthy. However, scientist Gary Lovett says the white balls which provide protection for the bugs are created by a tiny insect. It's hard to believe the tiny bug could kill a tree. However, trees can end up with millions and millions of the pests. When there are that many, it ends up killing the tree.
The bug from East Asia is slowly killing trees across the USA. The trouble－making bug is just one of many invasive(入侵的) pests that have slipped into the United States. They can hurt other living things in their new home.
Many invasive pests arrive on wooden pallets piled inside shipping containers. They support and separate goods, and keep them from sliding around. Invasive pests often tunnel into the pallets. How can we stop pests from riding on pallets? Lovett says new rules are needed. The companies that make pallets don't want more rules. Congress has added an amendment(修正案) in the 2018 Farm Bill to try and prevent this problem. However, Lovett is not hopeful it will make much of a difference. Pallets are checked by inspectors. Many are sprayed with bug－killing pesticide. "I believe in the system，" said Brent McClendon, president of The National Wooden Pallet and Container Association. He also said shipping containers are checked very carefully.
Still, each year 13 million containers are shipped to the U.S. Each is full of wooden pallets. Lovett says: "Inspectors can't possibly check everything. All it takes are a few bad pallets; we should get rid of wooden pallets." He believes pallets should be made of plastic or eco－composite wood. Eco－composite wood is a mix of wood fiber and plastic. Insects cannot hide into it. One problem is that these choices cost more. They may be worth the extra money, though. Invasive pests cost the U.S. $5 billion a year. Trees don't just die in forests. They also die in cities and our yards. Then, they need to be replaced. That costs money, too.
