Healthy Potatoes

Did you ever meet a plant doctor who spends his time looking at potatoes to see whether they are sick or healthy? Do you know how careful a farmer must be to keep his potato plants well?

Autumn is the time when potatoes are dug and stored for the winter. They should have smooth skins. Their flesh should be sound—without dark spots or streaks. They should, indeed, be healthy in the fall if they are to keep in good condition to eat during the winter, for sick potatoes are likely to rot or to become spoiled in other ways while they are lying in cellars or other storage places.

They must be well, too, if they are to serve as suitable seed potatoes in the spring.

Potatoes belong to the same plant family as tomatoes. A tomato plant has its seeds in fruits that grow in the flower clusters. So does a potato plant.

A man who wishes to have tomato plants in his garden grows them from seeds that are taken from ripe tomatoes. Potato plants, also, may be grown from seeds taken from ripe potato fruits.

However, for many good reasons, the farmer who grows potatoes for food does not plant potato seeds at all. He plants, instead, the potatoes themselves after he has cut them into suitable pieces. These are called seed potatoes or seed pieces, though there are no seeds in them. Potatoes have buds (often called "eyes"). Sprouts start from these buds and grow into new potato plants.

So you see that the farmer should have good sound seed potatoes to put away in the fall if healthy plants are to grow from them in the spring.

Even if the plants start from good potatoes, they may become ill later. Perhaps the plant doctor will come into the field and look at them and say, "These potatoes have late blight." 

Late blight is a disease caused by a kind of fungus.  Funguses (or fungi ) have no flowers or leaves. They cannot get food from the air and the soil, as can plants with green leaves. They must take their food from other plants or from animals. A toadstool,  or mushroom,  is a kind of large fungus. Molds on jelly or old bread are kinds of small fungi.

The kind of fungus that causes late blight is so small that you cannot see one of these fungi without a magnifying glass. Late blight may make brown places on the potato leaves. It may attack the stems and the potatoes in the ground.

If a potato that is sick with late blight is planted, the new potato plants that grow from it are likely to have late blight, too. The stalks of such plants may be slender and weak.

As you have just learned, a fungus does not have flowers. It does not have seeds either. Instead of seeds, it has spores.  The spores are very fine and blow about like dust.

Spores from the late-blight fungus may blow from sick leaves to well plants. They may be washed from the air on to plants by raindrops. So the disease may spread in damp weather. Sometimes whole fields of potatoes die from late blight.

Or the plant doctor may look at some potatoes and say, "They have blackleg. " The base of the stem of a potato plant sick with this disease becomes quite black. The potatoes may have bad-smelling, rotten places.

Blackleg is caused by a kind of bacterium.  A bacterium is a tiny living thing. Its body consists of only one small part called a cell. (Two or more of these little forms of life are called bacteria. ) Bacteria are so exceedingly small that hundreds of them could live in a drop no larger than the period at the end of this sentence.

Most kinds of bacteria are harmless. Many kinds are helpful to plants and animals. But some kinds cause diseases in plants or animals. Perhaps you know that diphtheria  and tuberculosis  are two kinds of diseases that bacteria may cause people to have.

There are still other kinds of potato diseases caused by fungi and bacteria. Late blight and blackleg are only two of them.

Sometimes plants become ill because aphids  carry the juice of sick plants in their mouths and take it to well plants. Aphids are small insects with sharp, slender mouth parts. They thrust their beaks into leaves or stems of plants and suck the juices. If they feed on sick potato plants and later put their beaks into well plants, they may give the healthy plants some diseases in this way.

You do not need to worry about eating sick potatoes. You will not have late blight or blackleg or any other potato disease even if you taste potatoes from sick plants. People and potatoes do not have the same diseases.

Farmers, however, worry about the health of their potatoes. They cannot get good crops of potatoes from sick plants. And such potatoes are likely to spoil in storage. So the farmers read books and bulletins that plant doctors have written about potato diseases. Then they try to keep their potatoes healthy.

They begin by giving their seed potatoes a bath before they cut them into seed pieces. They put something into the bath that prevents certain diseases.

After the potato plants are growing in the field, the farmers spray or dust them to keep them in good condition.

Bordeaux  is the name of one mixture that is used. This may be dusted over the plants in a dry form or mixed with water and put on as a spray. Bordeaux protects potatoes from late blight and some other diseases.

When a farmer wishes to get rid of the aphids on his potato plants, he is likely to use a poison with nicotine  in it. Nicotine is found in tobacco. This poison is mixed with other things and put on the plants as a dry dust or used in a wet spray. Nicotine kills aphids in a short time; so this is a useful poison.

Colorado potato beetles  are sometimes so numerous in a field that they could eat enough leaves to cause the plants to die unless something was done to stop them.

A Colorado potato beetle has bright tan wing covers with ten black stripes on them. It shuts the wing covers down over its back like a hard shell when it is not flying. The shell-like covers protect the thin red wings.

Less than one hundred years ago there were no beetles of this kind anywhere in our country except in the West near the Rocky Mountains. They lived on wild plants belonging to the Potato Family. They had never tasted potato leaves. After people planted potatoes in that part of the country, the beetles began to eat them. Each year some of them flew from one field to a new one farther on, until at last they reached all parts of the country where potatoes are grown.

The beetles lay their yellow eggs in clusters on the plants. The fat, reddish, wingless young that hatch from the eggs eat potato leaves even more greedily than the old beetles do.

Farmers save their potatoes from these insects by spraying the plants with a poison that has arsenic  in it. The pests eat the sprayed leaves and die.

Even if there were no insects and no diseases to attack potato plants, farmers would need to be rather careful of this crop, for they have to keep the soil in good condition. Potatoes grow best in soil that is slightly acid, but not too acid. If the soil is too acid for the potatoes, lime  must be added. Lime makes soil less acid. There must be, too, the right sort of plant food in the soil. Some food for plants is prepared in factories. It is one kind of fertilizer.  Farmers often buy it and put it on the soil.

After the crop is dug, the potatoes must still have care. They must be stored in places that are cold enough, but not too cold.

So, in one way and another, potatoes need attention all through the year. When you taste a white baked potato that is so perfect that even the skin is good to eat, you may think of the farmer who took care of the crop. You may like to think, too, of the plant doctors who have learned so much about keeping potatoes healthy.

What To Do after Reading Chapter Two

A POTATO SHOW

If your teacher approves, have a Potato Show at school. Perhaps a few members of your class will offer to bring samples of potatoes for the show.

Choose one of your class to pretend he is a plant doctor. Let the plant doctor say which potatoes he thinks look as if they have smooth, healthy skins. Let him cut a few of the potatoes to see whether the flesh is firm and sound or whether it has dark spots or streaks.

READ

Choose at least one of the following subjects to read:

(1) Aphids.  You have just read something about potato aphids. The story of another kind of aphid may be found in the chapter of Holiday Pond  that is called "Nim Fay, the Sap-Drinker."

On pages 12–16 in Chapter 1 in First Lessons in Nature Study  there is a section called "Aphids and Honeydew."

(2) Beetles.  You have just read something about potato beetles. The story of another kind of beetle may be found in Hexapod Stories  in the chapter called "Lampy's Fourth o' July."

(3) Tubers.  Read "Tubers" on pages 65–67 in Chapter 3 in First Lessons in Nature Study.

ANSWER THREE QUESTIONS

Here are six questions. Answer any three of them.

(1) Does an aphid chew the leaves of a plant? If not, how does it feed?

(2) Tell two ways in which aphids may harm a plant.

(3) Look at the pictures of some aphids and some beetles. Then tell how the wings of an aphid differ from those of a beetle.

(4) Write a list of all the different kinds of beetles whose names you can remember.

(5) Tell one fact about each beetle in your list.

(6) Does a beetle chew food or suck it?

TUBERS, ROOTS, AND BULBS

White potatoes are called tubers.  These tubers are thickened underground stems. Beets, carrots, and turnips are thickened roots. Onions, as you know, are thickened underground leaf buds or bulbs.

Look at a potato, a carrot (or beet or turnip), and an onion. Are there any roots on the potato tuber? Are there any "eyes" on the carrot or onion?

Cut a potato, a carrot, and an onion in halves. What differences do you find inside?