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.

In Scotland there once lived a poor shepherd whose name was James Hogg. It was his business to take care of the sheep which belonged to a rich landholder by the Ettrick Water. Sometimes he had several hundreds of lambs to look after. He drove them to the pastures(牧场) on the hills and watched them day after day while they fed on the short green grass.

He had a dog which was called Syrah. This dog helped him watch the sheep. He would drive them from place to place as his master wished. Sometimes he would take care of the whole flock while the shepherd was resting or eating his dinner.

One dark night James Hogg was on the hilltop with a flock of seven hundred lambs. Syrah was with him. Suddenly a storm came up. There was thunder and lightning ; the wind blew hard ; the rain poured. The poor lambs were frightened. The shepherd and his dog could not keep them together. Some of them ran towards the east, some towards the west, and some towards the south. The shepherd soon lost sight of them in the darkness. With lighted lantern in his hand, he went up and down the rough hills calling for his lambs.

Two or three other shepherds joined him in the search. All night long they sought(寻找) for the lambs. At last James Hogg said, “It’s of no use. All what we can do is to go home and tell the master that we have lost his whole flock.” They had walked a mile or two towards home, when they came to the edge of a narrow and deep valley. They looked down, and at the bottom they saw some lambs huddled(蜷缩) together among the rocks. And there was Syrah standing guard over them. They counted them and were surprised to find that not one lamb of the great flock of seven hundred was missing.

I bought several packs of seeds, 24 small plastic seed pots, plant fertilizer and potting soil. I made sure the soil didn't contain added fertilizer. I wanted something that I could grow quickly, that wouldn't take up a lot of space and that wouldn't get too big. I ran this experiment in early fall in Maryland. So I knew I needed a plant that could grow when it's cool. I picked radishes (小萝卜), which grow well in the early fall or spring. Some varieties can grow a full radish in only 21 days.

I kept 12 of the pots and one pack of seeds for myself. I gave the other 12 pots and the other packet of seeds — along with some fertilizer and soil — to my editor, Sarah. This was to provide an additional control for location. After all, what if my yard just happens to be much better for growing plants? What if it's worse? By dividing the plants up between my yard and Sarah's, I hoped to make sure that any difference with the plants came from the fertilizer.

Sarah and I planted our seeds. Sometimes, seeds don’t sprout (发芽). So we carefully planted four evenly (相等地) spaced seeds in each pot. Six of my pots (and six of Sarah’s) served as controls — pots that would not get fertilizer. Our other six were treated with fertilizer. For each of us, this added up to 24 control seeds, and 24 seeds that would get fertilizer.

We watered all the plants equally with clean water every other day (unless it rained). Once a week, we applied fertilizer to half the pots. We also took pictures every day, so we could see the plants change over time. As I expected, many of our seeds didn't sprout. In fact, only about a fourth of mine sprouted. Sarah has a greener thumb. She successfully grew half of hers.