Prevention of Plant Disease

Prevention of Plant Disease

In the last two sections you have learned something of the nature of those fungi and bacteria that cause disease in animals and plants. Now let us see how we can use this knowledge to lessen the diseases of our crops. Farmers lose through plant diseases much that could be saved by proper precaution.

First, you must remember that every diseased fruit, twig, or leaf bears millions of spores. These must be destroyed by burning. They must not be allowed to lie about and spread the disease in the spring. See that decayed fruit in the bin or on the trees is destroyed in the same manner. Never throw decayed fruit into the garden or orchard, as it may cause disease the following year.

So that you may not spread disease

So that you may not spread disease

So that you may not spread disease

Bacteria are so small that they are readily borne on the dust particles of the air and are often taken into the body through the breath and also through water or milk. You can therefore see how careful you should be to prevent germs from getting into the air or into water or milk when there is disease about your home. You should heed carefully all instructions of your physician on this point, so that you may not spread disease.

You see that some of the yeast plants and bacteria

You see that some of the yeast plants and bacteria

You see that some of the yeast plants and bacteria

You see that some of the yeast plants and bacteria, as many of these forms are called, are very friendly to us, while others do us great harm.

Some bacteria grow within the bodies of men and other animals or in plants. When they do so they may produce disease. Typhoid fever, diphtheria, consumption, and many other serious diseases are caused by bacteria. Fig. 118, e, shows the bacterium that causes typhoid fever. In the picture, of course, it is very greatly magnified. In reality these bacteria are so small that about twenty-five thousand of them side by side would extend only one inch. These small beings produce their great effects by very rapid multiplication and by giving off powerful poisons.

When you see any decaying matter you may

When you see any decaying matter you may

When you see any decaying matter you may

When you see any decaying matter you may know that in it minute plants much like the yeast plant are at work. Since decay is due to them, we take advantage of the fact that they cannot grow in strong brine or smoke; and we prepare meat for keeping by salting it or by smoking it or by both of these methods.

Fig. 118. Forms of Bacteria
a, grippe;
b, bubonic plague;
c, diphtheria;
d, tuberculosis;
e, typhoid fever

The cider will not ferment or sour as it did before

The cider will not ferment or sour as it did before

The cider will not ferment or sour as it did before

Later, other kinds of plants equally small will grow and change the alcohol into an acid which you will recognize as vinegar by its sour taste and peculiar odor. Thus vinegar is made by the action of two different kinds of little living plants in the cider. That these are living beings you can prove by heating the cider and keeping it tightly sealed so that nothing can enter it. You will find that because the living germs have been killed by the heat, the cider will not ferment or sour as it did before. The germs could of course be killed by poisons, but then the cider would be unfit for use. It is this same little yeast plant that causes bread to rise.

Yeast And Bacteria

Yeast And Bacteria

Can you imagine a plant so small that it would take one hundred plants lying side by side to equal the thickness of a sheet of writing-paper? There are plants that are so small. Moreover, these same plants are of the utmost importance to man. Some of them do him great injury, while others aid him very much.

You will see their importance when you are told that certain of them in their habits of life cause great change in the substances in which they live. For example, when living in a sugary substance they change the sugar into a gas and an alcohol. Do you remember the bright bubbles of gas you have seen rising in sweet cider or in wine as it soured? These bubbles are caused by one of these small plants—the yeast plant. As the yeast plant grows in the sweet fruit juice, alcohol is made and a gas is given off at the same time, and this gas makes the bubbles.

Fig. 117. Yeast Plants
A, a single plant;
B, group of two budding cells;
C, group of several cells

EXERCISE

EXERCISE

EXERCISE

EXERCISE

Why do things mold more readily in damp places? Do you now understand why fruit is heated before it is canned? Try to grow several kinds of mold. Do you know any fungi which may be eaten?

Transfer disease from a rotten apple to a healthy one and note the rapidity of decay. How many really healthy leaves can you find on a strawberry plant? Do you find any spots with reddish borders and white centers? Do you know that this is a serious disease of the strawberry? What damage does fruit mold do to peaches, plums, or strawberries?

Write to your experiment station for bulletins on plant diseases and methods for making and using spraying mixtures.

One such poison is the Bordeaux

One such poison is the Bordeaux

One such poison is the Bordeaux

You see, then, that fungi are living plants that grow at the expense of other plants and cause disease. Now if you can cover the leaf with a poison that will kill the spore when it comes, you can prevent the disease. One such poison is the Bordeaux (bôr-dō') mixture, which has proved of great value to farmers.

Since the fungus in most cases lives within the leaves, the poison on the outside does no good after the fungus is established. The treatment can be used only to prevent attack, not to cure, except in the case of a few mildews that live on the outside of the leaf, as does the rose mildew.

Use one ounce of the liver of sulphur to two gallons of water

Use one ounce of the liver of sulphur to two gallons of water

Use one ounce of the liver of sulphur to two gallons of water

Mildew on the rose or on any other plant may be killed by spraying the leaves with a solution of liver of sulphur; to make this solution, use one ounce of the liver of sulphur to two gallons of water.

The fungus that causes the pear-leaf spots has its spores in little pits (Fig. 115). The spores of some fungi also grow on stalks, as shown in Fig. 116. This figure represents an enlarged view of the pear scab, which causes so much destruction.

Just as the fungus studied above lives in the apple or bread

Just as the fungus studied above lives in the apple or bread

Just as the fungus studied above lives in the apple or bread

Just as the fungus studied above lives in the apple or bread, so other varieties live on leaves, bark, etc. Fig. 113 represents the surface of a mildewed rose leaf greatly magnified. This mildew is a fungus. You can see its creeping stems, its upright stalk, and numerous spores ready to fall off and spread the disease with the first breath of wind. You must remember that this figure is greatly magnified, and that the whole portion shown in the figure is only about one tenth of an inch across. Fig. 114 shows the general appearance of a twig affected by this disease.

It cannot pierce healthy apple skin

It cannot pierce healthy apple skin

It cannot pierce healthy apple skin

The same blue mold that grows on bread often attacks apples that have been slightly bruised; it cannot pierce healthy apple skin. You can plant the mold in the bruised apple just as you did on bread and watch its rapid spread through the apple. You learn from this the need of preventing bruised or decayed apples from coming in contact with healthy fruit.

Fig. 116. Spores of the Pear Scab
The spores are borne on stalks

The little plants which make up these molds are called fungi

The little plants which make up these molds are called fungi

The little plants which make up these molds are called fungi

The little plants which make up these molds are called fungi. Some fungi, such as the toadstools, puffballs, and devil's snuff-box, are quite large; others, namely the molds, are very small; and others are even smaller than the molds. Fungi never have the green color of ordinary plants, always reproduce by spores, and feed on living matter or matter that was once alive. Puffballs, for example, are found on rotting wood or dead twigs or roots. Some fungi grow on living plants, and these produce plant disease by taking their nourishment from the plant on which they grow; the latter plant is called the host.

Possibly this experiment will help us

Possibly this experiment will help us

Possibly this experiment will help us

It is also of great importance to decide whether by keeping the spores away we may prevent mold. Possibly this experiment will help us. Moisten a piece of bread, then dip a match or a pin into the blue mold on a lemon, and draw the match across the moist bread. You will thus plant the spores in a row, though they are so small that perhaps you may not see any of them. Place the bread in a damp place for a few days and watch it. Does the mold grow where you planted it? Does it grow elsewhere? This experiment should prove to you that molds are living things and can be planted. If you find spots elsewhere, you must bear in mind that these spores are very small and light and that some of them were probably blown about when you made your sowing. When you touch the moldy portion of a dry lemon, you see a cloud of dust rise. This dust is made of millions of spores.

If you cut a lemon and let it stand for a day or two

If you cut a lemon and let it stand for a day or two

If you cut a lemon and let it stand for a day or two

If you cut a lemon and let it stand for a day or two, there will probably appear a blue mold like that you have seen on the surface of canned fruit. Bread also sometimes has this blue mold; at other times bread has a black mold, and yet again a pink or a yellow mold.

These and all other molds are tiny living plants. Instead of seeds they produce many very small bodies that serve the purpose of seeds and reproduce the mold. These are called spores. Fig. 112 shows how they are borne on the parent plant.

Fig. 113. Magnified Rose Mildew

Fig. 114. A Mildewed Rose

It was this that caused the apple to decay

It was this that caused the apple to decay

It was this that caused the apple to decay

Sometimes when the skin of a rotten apple has been broken you will find in the broken place a blue mold. It was this that caused the apple to decay. This mold is a living plant; very small, certainly, but nevertheless a plant. Let us learn a little about molds, in order that we may better understand our apple and potato rots, as well as other plant diseases.

Many of these diseases are contagious

Many of these diseases are contagious

Many of these diseases are contagious

Many of the yellowish or discolored spots on leaves are the result of disease, as is also the smut of wheat, corn, and oats, the blight of the pear, and the wilt of cotton. Many of these diseases are contagious, or, as we often hear said of measles, "catching." This is true, among others, of the apple and peach rots. A healthy apple can catch this disease from a sick apple. You often see evidence of this in the apple bin. So, too, many of the diseases found in the field or garden are contagious.

It costs farmers millions of dollars annually

It costs farmers millions of dollars annually

It costs farmers millions of dollars annually

You have all seen rotten fruit. This is diseased fruit. Fruit rot is a plant disease. It costs farmers millions of dollars annually. A fruit-grower recently lost sixty carloads of peaches in a single year through rot which could have been largely prevented if he had known how.

Fig. 112. Tangled Threads of Blue Mold

The Cause And Nature of Plant Disease

The Cause And Nature of Plant Disease

Plants have diseases just as animals do; not the same diseases, to be sure, but just as serious for the plant. Some of them are so dangerous that they kill the plant; others partly or wholly destroy its usefulness or its beauty. Some diseases are found oftenest on very young plants, others prey on the middle-aged tree, while still others attack merely the fruit. Whenever a farmer or fruit-grower has disease on his plants, he is sure to lose much profit.

If the temperature is from 50° to 90°

If the temperature is from 50° to 90°

If the temperature is from 50° to 90°

If the temperature is from 50° to 90°, averaging 70°, try abutilon, begonia, bouvardia, caladium, canna, Cape jasmine, coleus, fuchsia, gloxinia, heliotrope, lantana, lobelia, roses, and smilax.

If your box or window is shaded a good part of the time, raise begonias, camellias, ferns, and Asparagus Sprengeri.

Fig. 111. Ferns for Both Indoors and Outdoors

When the soil is dry, water it; then apply no more water until it again becomes dry. Beware of too much water. The plants should be washed occasionally with soapsuds and then rinsed. If red spiders are present, sponge them off with water as hot as can be borne comfortably by the hand. Newspapers afford a good means of keeping off the cold.

The soil must be rich and loose

The soil must be rich and loose

The soil must be rich and loose

The soil must be rich and loose. The best contains some undecayed organic matter such as leaf-mold or partly decayed sods and some sand. Raise your plants from bulbs, cuttings, or seed, just as in outdoor gardens. Some plants do better in cool rooms, others in a warmer temperature.

If the temperature ranges from 35° to 70°, averaging about 55°, azaleas, daisies, carnations, candytuft, alyssum, dusty miller, chrysanthemums, cinerarias, camellias, daphnes, geraniums, petunias, violets, primroses, and verbenas make especially good growths.

A BEAUTIFUL WINDOW FLOWER

The window-garden may vary in size from an

The window-garden may vary in size from an

The window-garden may vary in size from an

The window-garden may vary in size from an eggshell holding a minute plant to boxes filling all the available space about the window. The soil may be in pots for individual plants or groups of plants or in boxes for collections of plants. You may raise your flowers inside of the window on shelves or stands, or you may have a set of shelves built outside of the window and inclosed in glazed sashes. The illustration on page 119 gives an idea of such an external window-garden.

Fig. 110. Making the Outside of a Window Bloom

And is a means of beautifying the room at very small expense

And is a means of beautifying the room at very small expense

And is a means of beautifying the room at very small expense

Window-Gardening. Growing plants indoors in the window possesses many of the attractions of outdoor flower-gardening, and is a means of beautifying the room at very small expense. Especially do window-gardens give delight during the barren winter time. They are a source of culture and pleasure to thousands who cannot afford extended and expensive ornamentation.

Do not let the plants go to seed

Do not let the plants go to seed

Do not let the plants go to seed

To make your plants do best, cultivate them carefully. Allow no weeds to grow among them and do not let the surface of the soil dry into a hard crust. Beware, however, of stirring the soil too deep. Loosening the soil about the roots interrupts the feeding of the plant and does harm. Climbing plants may be trained to advantage on low woven-wire fences. These are especially serviceable for sweet peas and climbing nasturtiums. Do not let the plants go to seed, since seeding is a heavy drain on nourishment. Moreover, the plant has served its end when it seeds and is ready then to stop blossoming. You should therefore pick off the old flowers to prevent their developing seeds. This will cause many plants which would otherwise soon stop blossoming to continue bearing flowers for a longer period.

Fig. 109. An Inside Window Box in its Full Glory

Of perennials select bleeding-hearts

Of perennials select bleeding-hearts

Of perennials select bleeding-hearts

Of perennials select bleeding-hearts, pinks, bluebells, hollyhocks, perennial phlox, perennial hibiscus, wild asters, and goldenrods. From bulbs choose crocus, tulip, daffodil, narcissus, lily of the valley, and lily.

Some climbers are cobæa, honeysuckle, Virginia creeper, English ivy, Boston ivy, cypress vine, hyacinth bean, climbing nasturtiums, and roses.

Fig. 108. A Window-Garden

The kinds of flowers that you can grow are almost countless

The kinds of flowers that you can grow are almost countless

The kinds of flowers that you can grow are almost countless

The kinds of flowers that you can grow are almost countless. You can hardly make a mistake in selecting, as all are interesting. Start this year with a few and gradually increase the number under your care year by year, and aim always to make your plants the choicest of their kind.

Of annuals there are over four hundred kinds cultivated. You may select from the following list: phlox, petunias, China asters, California poppies, sweet peas, pinks, double and single sunflowers, hibiscus, candytuft, balsams, morning-glories, stocks, nasturtiums, verbenas, mignonette.

Fig. 107. A Window Box

Many of our ornamental evergreen trees

Many of our ornamental evergreen trees

Many of our ornamental evergreen trees

Many of our ornamental evergreen trees, such as the arbor vitæ, can be grown in the spring from seeds sowed in a frame. Cotton cloth should be stretched over the trees while they are young, to prevent the sun from scorching them. When a year old they may be set in nursery rows to develop until they are large enough to plant. Arbor vitæ may also be grown from cuttings made by setting young tips in boxes of sand in the fall and keeping them warm and moist through the winter. Most of them will be rooted by spring.

Fig. 106. Four-O'clocks set in a Good Place

A light cover of pine leaves will prevent damage from frost

A light cover of pine leaves will prevent damage from frost

A light cover of pine leaves will prevent damage from frost

Perennial plants, such as our flowering shrubs, are grown from cuttings of the ripe wood after the leaves have fallen in autumn. From North Carolina southward these cuttings should be set in rows in the fall. Cuttings ten inches long are set so that the tops are just even with the ground. A light cover of pine leaves will prevent damage from frost. Farther north the cuttings should be tied in bundles and well buried in the ground with earth heaped over them. In the spring set them in rows for rooting. In the South all the hardy hybrid perpetual roses can be grown in this way, and in any section the cuttings of most of the spring-flowering shrubs will grow in the same manner. The Japanese quince, which makes such a show of its scarlet flowers in early spring, can be best grown from three-inch cuttings made of the roots and planted in rows in the fall.

The canna makes large fleshy roots which in the North are taken up

The canna makes large fleshy roots which in the North are taken up

The canna makes large fleshy roots which in the North are taken up

The canna makes large fleshy roots which in the North are taken up, covered with damp moss, and stored under the benches of the greenhouse or in a cellar. If allowed to get too dry, they will wither. From central North Carolina south it is best to cover them up thickly with dead leaves and let them stay in the ground where they grew. In the early spring take them up and divide for replanting.

The sweet pea is one of the most popular flowers grown in this way

The sweet pea is one of the most popular flowers grown in this way

The sweet pea is one of the most popular flowers grown in this way

Many kinds of flower-seeds may be sowed directly in the open ground where they are to remain. The sweet pea is one of the most popular flowers grown in this way. The seeds should be sowed rather thickly in rows and covered fully four inches deep. The sowing should be varied in time according to the climate. From North Carolina southward, sweet peas may be sowed in the fall or in January, as they are very hardy and should be forced to bloom before the weather becomes hot. Late spring sowing will not give fine flowers in the South. From North Carolina northward the seeds should be sowed just as early in the spring as the ground can be easily worked. When the plants appear, stakes should be set along the rows and a strip of woven-wire fence stretched for the plants to climb on. Morning-glory seeds are also sowed where they are to grow. The seeds of the moonflower are large and hard and will fail to grow unless they are slightly cut. To start their growth make a slight cut just through the hard outer coat of the seed so as to expose the white inside. In this way they will grow very readily. The seeds of the canna, or Indian-shot plant, are treated in a similar way to start them growing.

Fig. 105. Dahlias

In this class we find begonias

In this class we find begonias

In this class we find begonias

There are many flower-seeds which are so small that they must not be covered at all. In this class we find begonias, petunias, and Chinese primroses. To sow these prepare boxes as for the other seeds, and press the earth smooth. Then scatter some fine, dry moss thinly over the surface of the soil. Sprinkle this with water until it is well moistened, and at once scatter the seeds thinly over the surface and cover the boxes with panes of glass until the seeds germinate. Transplant as soon as the young plants can be lifted out separately on the blade of a penknife.

Fig. 104. A Modern Sweet Pea

As soon as the seedlings have made a second pair of leaves

As soon as the seedlings have made a second pair of leaves

As soon as the seedlings have made a second pair of leaves

As soon as the seedlings have made a second pair of leaves, take them up with the point of a knife and transplant them into other boxes filled in the same way. They should be set two inches apart so as to give them room to grow strong. They may be transplanted from the boxes to the flower-garden by taking an old knife-blade and cutting the earth into squares, and then lifting the entire square with the plant and setting it where it is wanted.

Fig. 103. A Cyclamen

For seeds need to be covered according to their size

For seeds need to be covered according to their size

For seeds need to be covered according to their size

Seeds sowed in the same box should be of the same general size in order that they may be properly covered, for seeds need to be covered according to their size. After sowing the seed, sift the fine soil over the surface of the box. The best soil for covering small seeds is made by rubbing dry moss and leaf-mold through a sieve together. This makes a light cover that will not bake and will retain moisture. After covering the seeds, press the soil firm and smooth with a wooden block. Now sprinkle the covering soil lightly with a watering-pot until it is fairly moistened. Lay some panes of glass over the box to retain the moisture, and avoid further watering until moisture becomes absolutely necessary. Too much watering makes the soil too compact and rots the seed.

In growing annual plants from seed

In growing annual plants from seed

In growing annual plants from seed

In growing annual plants from seed, there is little difficulty if the grower has a greenhouse or a hotbed with a glass sash. Even without these the plants may be grown in shallow boxes in a warm room. The best boxes are about four inches deep with bottoms made of slats nailed a quarter of an inch apart to give proper drainage. Some moss is laid over the bottom to prevent the soil from sifting through. The boxes should then be filled with light, rich soil. Fine black forest mold, thoroughly mixed with one fourth its bulk of well-rotted manure, makes the best soil for filling the seed-boxes. If this soil be placed in an oven and heated very hot, the heat will destroy many weeds that would otherwise give trouble. After the soil is put in the boxes it should be well packed by pressing it with a flat wooden block. Sow the seeds in straight rows, and at the ends of the rows put little wooden labels with the names of the flowers on them.

Fig. 102. The Poet's Narcissus

They are generally used to originate new varieties

They are generally used to originate new varieties

They are generally used to originate new varieties

There are many perennial plants that will bloom the first season when grown from the seed, though such seedlings are seldom so good as the plants from which they came. They are generally used to originate new varieties. Seeds of the dahlia, for instance, can be sowed in a box in a warm room in early March, potted as soon as the plants are large enough to handle, and finally planted in the garden when the weather is warm. They will bloom nearly as soon as plants grown by dividing the roots or from cuttings.

Fig. 100. Outdoor-Grown Chrysanthemums

Fig. 101. The Carnation (Eldorado)

But there are no eyes on them as there are on the sweet potato

But there are no eyes on them as there are on the sweet potato

But there are no eyes on them as there are on the sweet potato

The dahlia makes a mass of roots that look greatly like sweet potatoes, but there are no eyes on them as there are on the sweet potato. The only eyes are on the base of the stem to which they are joined. They may be sprouted like sweet potatoes and then soft cuttings made of the green shoots, after which they may be rooted in the greenhouse and later planted in pots.