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separation between diseased and healthy wood? If so, the bacteria are still living in the cambium. Cut out a small bit of the diseased portion and insert it under the bark of a healthy, juicy twig within a few inches of its tip and watch it from day to day. Does the tree catch the disease? This experiment may prove to you how easily the disease spreads. If you should see any drops like dew hanging from diseased twigs, touch a little of this moisture to a healthy flower and watch for results.

Cut and burn all diseased twigs that you can find. Estimate the damage done by fire-blight.

Farmers' bulletins on orchard enemies are published by the Department of Agriculture, Washington, D.C., and can be had by writing for them. They will help your father much in treating fire-blight.

Oat Smuts. Let us go out into a near-by oat field and look for all the blackened heads of grain that we can find. How many are there? To count accurately let us select an area one foot square. We must look carefully, for many of these blackened heads are so low that we shall not see them at the first glance. You will be surprised to find as many as thirty or forty heads in every hundred so blackened. These blackened heads are due to a plant disease called smut.

Fig. 121.
Fig. 121. Loose Smut
of Oats

The glumes at a
more nearly destroyed
than the glumes at b
Fig. 122.
Fig. 122. A Crop from Oats
treated with Formalin

When threshing-time comes you will notice a great quantity of black dust coming from the grain as it passes through the machine. The air is full of it. This black dust consists of the spores of a tiny fungous plant. The fungous smut plant grows upon the oat plant, ripens its spores in the head, and is ready to be thoroughly scattered among the grains of the oats as they come from the threshing-machine.

These spores cling to the grain and at the next planting are ready to attack the sprouting plantlet. A curious thing about the smut is that it can gain a foothold only on very young oat plants; that is, on plants about an inch long or of the age shown in Fig. 121.

When grain covered with smut spores is planted, the spores develop with the sprouting seeds and are ready to attack the young plant as it breaks through the seed-coat. You see, then, how important it is to have seed grain free from smut. A substance has been found that will, without injuring the seeds, kill all the smut spores clinging to the grain. This substance is called formalin. Enough seed to plant a whole acre can be treated with formalin at a cost of only a few cents. Such treatment insures a full crop and clean seed for future planting. Try it if you have any smut.

Fig. 122 illustrates what may be gained by using seeds treated to prevent smut. The annual loss to the farmers of the United States from smut on oats amounts to several millions of dollars. All that is needed to prevent this loss is a little care in the treatment of seed and a proper rotation of crops.

EXERCISE

Count the smutted heads on a patch three feet square and estimate the percentage of smut in all the wheat and oat fields near your home. On which is it most abundant? Do you know of any fields that have been treated for smut? If so, look for smut in these fields. Ask how they were treated. Do you know of any one who uses bluestone for wheat smut? Can oats be treated with bluestone?

At planting time get an ounce of formalin at your drug store or from the state experiment station. Mix this with three gallons of water. This amount will treat three bushels of seeds. Spread the seeds thinly on the barn floor and sprinkle them with the mixture, being careful that all the seeds are thoroughly moistened. Cover closely with blankets for a few hours and plant very soon after treatment. Try this and estimate the per cent of smut at next harvest-time. Write to your experiment station for a bulletin on smut treatment.

Fig. 123.
Fig. 123. A Scabby Seed Potato
Fig. 124.
Fig. 124. A Healthy Seed Potato

Potato Scab. The scab of the white, or Irish, potato is one of the commonest and at the same time most easily prevented of plant diseases. Yet this disease diminishes the profits of the potato-grower very materially. Fig. 123 shows a very scabby potato, while Fig. 124 represents a healthy one. This scab is caused by a fungous growth on the surface of the potato. Of course it lessens the selling-price of the potatoes. If seed potatoes be treated to a bath of formalin just before they are planted, the formalin will kill the fungi on the potatoes and greatly diminish the amount of scab at the next harvest. Therefore before they are planted, seed potatoes should be soaked in a weak solution of formalin for about two hours. One-half pint of formalin to fifteen gallons of water makes a proper solution.

Fig. 125.
Fig. 125.
From a scabby potato,
like the one in Fig. 123,
this yield was obtained
Fig. 126.
Fig. 126.
From a healthy potato,
like the one in Fig. 124,
this yield was obtained

One pint of formalin, or enough for thirty gallons of water, will cost but thirty-five cents. Since this solution can be used repeatedly, it will do for many bushels of seed potatoes.

Fig. 127.
Fig. 127. Effect of Spraying
Sprayed potatoes on left; unsprayed on right

Late Potato Blight. The blight is another serious disease of the potato. This is quite a different disease from the scab and so requires different treatment. The blight is caused by another fungus, which attacks the foliage of the potato plant. When the blight seriously attacks a crop, it generally destroys the crop completely. In the year 1845 a potato famine extending over all the United States and Europe was caused by this disease.

Fig. 128.
Fig. 128. Yield from Two Fields of the Same Size
The one at the top was sprayed; the one at the bottom was unsprayed

Spraying is the remedy for potato blight. Fig. 128 shows the effect of spraying upon the yield. In this case the sprayed field yielded three hundred and twenty-four bushels an acre, while the unsprayed yielded only one hundred bushels to an acre. Fig. 127 shows the result of three applications of the spraying mixture on the diseased field. Figs. 129 and 130 show how the spraying is done.

Fig. 129.
Fig. 129. Spraying Machine


Fig. 130.
Fig. 130. Spraying Machine

EXERCISE

Watch the potatoes at the next harvest and estimate the number that is damaged by scab. You will remember that formalin is the substance used to prevent grain smuts. Write to your state experiment station for a bulletin telling how to use formalin, as well as for information regarding other potato diseases. Give the treatment a fair trial in a portion of your field this year and watch carefully for results. Make an estimate of the cost of treatment and of the profits. How does the scab injure the value of the potato? The late blight can often be recognized by its odor. Did you ever smell it as you passed an affected field?

Fig. 131.
Fig. 131. Club Root

Club Root. Club root is a disease of the cabbage, turnip, cauliflower, etc. Its general effect is shown in the illustration (Fig. 131). Sometimes this disease does great damage. It can be prevented by using from eighty to ninety bushels of lime to an acre.

Black Knot. Black knot is a serious disease of the plum and of the cherry tree. It attacks the branches of the tree; it is well illustrated in Fig. 132. Since it is a contagious disease, great care should be exercised to destroy all diseased branches of either wild or cultivated plums or cherries. In many states its destruction is enforced by law. All black knot should be cut out and burned some time before February of each year. This will cost little and save much.

Fig. 132.
Fig. 132. Black Knot
Fig. 133.
Fig. 133. Moldy Peaches
Fig. 134.
Fig. 134. Peach Mummies

Peach Leaf Curl. Peach leaf curl does damage amounting to about $3,000,000 yearly in the United States. It can be almost entirely prevented by spraying the tree with Bordeaux mixture or lime-sulphur wash before the buds open in the spring. It is not safe to use strong Bordeaux mixture on peach trees when they are in leaf.

Cotton Wilt. Cotton wilt when it once establishes itself in the soil completely destroys the crop. The fungus remains in the soil, and no amount of spraying will kill it. The only known remedy is to cultivate a resistant variety of cotton or to rotate the crop.

Fruit Mold. Fruit mold, or brown rot, often attacks the unripe fruit on the tree, and turns it soft and brown and finally fuzzy with a coat of mildew. Fig. 133 shows some peaches thus attacked. Often the fruits do not fall from the trees but shrivel up and become "mummies" (Fig. 134). This rot is one of the most serious diseases of plums and peaches. It probably diminishes the value of the peach harvest from 50 to 75 per cent. Spraying according to the directions in the Appendix will kill the disease.

Fig. 135.


Fig. 135.
Fig. 135. Half of Tree sprayed to prevent Peach Curl
Note the difference in foliage and fruit on the sprayed and unsprayed halves of the tree, and the difference in yield shown below

CHAPTER VII ORCHARD, GARDEN, AND FIELD INSECTS SECTION XXXI. INSECTS IN GENERAL
Fig. 136.
Fig. 136. Ants

The farmer who has fought "bugs" on crop after crop needs no argument to convince him that insects are serious enemies to agriculture. Yet even he may be surprised to learn that the damage done by them, as estimated by good authority, amounts to millions and millions of dollars yearly in the United States and Canada.

Every one thinks he knows what an insect is. If, however, we are willing in this matter to make our notion agree with that of the people who have studied insects most and know them best, we must include among the true insects only such air-breathing animals as have six legs, no more, and have the body divided into three parts—head, thorax, and abdomen. These parts are clearly shown in Fig. 136, which represents the ant, a true insect. All insects do not show the divisions of the body so clearly as this figure shows them, but on careful examination you can usually make them out. The head bears one pair of feelers, and these in many insects serve also as organs of smell and sometimes of hearing. Less prominent feelers are to be found in the region of the mouth. These serve as organs of taste.

Fig. 137.
Fig. 137. Parts of an Insect
Fig. 138.
Fig. 138. Compound Eye
Of Dragon Fly

The eyes of insects are especially noticeable. Close examination shows them to be made up of a thousand or more simple eyes. Such an eye is called a compound eye. An enlarged view of one of these is shown in Fig. 138.

Attached to the thorax are the legs and also the wings, if the insect has wings. The rear portion is the abdomen, and this, like the other parts, is composed of parts known as segments. The insect breathes through openings in the abdomen and thorax called spiracles (see Fig. 137).

An examination of spiders, mites, and ticks

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