Insects lay many eggs and reproduce with remarkable rapidity

Insects lay many eggs and reproduce with remarkable rapidity

Insects lay many eggs and reproduce with remarkable rapidity

Insects lay many eggs and reproduce with remarkable rapidity. Their number therefore makes them a foe to be much dreaded. The queen honeybee often lays as many as 4000 eggs in twenty-four hours. A single house fly lays between 100 and 150 eggs in one day. The mosquito lays eggs in quantities of from 200 to 400. The white ant often lays 80,000 in a day, and so continues for two years, probably laying no less than 40,000,000 eggs. In one summer the bluebottle fly could have 500,000,000 descendants if they all lived. The plant louse, at the end of the fifth brood, has laid in a single year enough eggs to produce 300,000,000 young. Of course every one knows that, owing to enemies and diseases (for the insects have enemies which prey on them just as they prey on plants) comparatively few of the insects hatched from these eggs live till they are grown.

Do not completely change their form

Do not completely change their form

Do not completely change their form

Some insects, the grasshopper for example, do not completely change their form. Fig. 147 represents some young grasshoppers, which very closely resemble their parents.

Fig. 143. Butterfly

Fig. 144. Structure of the Caterpillar

Fig. 145. Moth Pupa in Cocoon

Fig. 146. A Butterfly Pupa
Note outline of the butterfly

Fig. 147. The Growth of a Grasshopper

It is generally the larvæ that do the most harm

It is generally the larvæ that do the most harm

It is generally the larvæ that do the most harm

From this you can see that it is especially important to know all you can about the life of injurious insects, since it is often easier to kill these pests at one stage of their life than at another. Often it is better to aim at destroying the seemingly harmless beetle or butterfly than to try to destroy the larvæ that hatch from its eggs, although, as you must remember, it is generally the larvæ that do the most harm. Larvæ grow very rapidly; therefore the food supply must be great to meet the needs of the insect.

Fig. 142. Moth and Cocoon

The egg hatches into a worm-like animal known as a grub

The egg hatches into a worm-like animal known as a grub

The egg hatches into a worm-like animal known as a grub

Many insects change their form from youth to old age so much that you can scarcely recognize them as the same creatures. First comes the egg. The egg hatches into a worm-like animal known as a grub, maggot, or caterpillar, or, as scientists call it, a larva. This creature feeds and grows until finally it settles down and spins a home of silk, called a cocoon (Fig. 145). If we open the cocoon we shall find that the animal is now covered with a hard outside skeleton, that it cannot move freely, and that it cannot eat at all. The animal in this state is known as the pupa (Figs. 145 and 146). Sometimes, however, the pupa is not covered by a cocoon, sometimes it is soft, and sometimes it has some power of motion (Fig. 141). After a rest in the pupa stage the animal comes out a mature insect (Figs. 142 and 143).

It is important to know how insects take their food

It is important to know how insects take their food

It is important to know how insects take their food

It is important to know how insects take their food, for by knowing this we are often able to destroy insect pests. Some are provided with mouth parts for chewing their food; others have a long tube with which they pierce plants or animals and, like the mosquito, suck their food from the inside. Insects of this latter class cannot of course be harmed by poison on the surface of the leaves on which they feed.

Fig. 141. Beetle
a, larva;
b, pupa;
c, adult;
d, burrow

The chief classes of insects are as follows

The chief classes of insects are as follows

The chief classes of insects are as follows

The chief classes of insects are as follows: the flies, with two wings only; the bees, wasps, and ants, with four delicate wings; the beetles, with four wings—two hard, horny ones covering the two more delicate ones. When the beetle is at rest its two hard wings meet in a straight line down the back. This peculiarity distinguishes it from the true bug, which has four wings. The two outer wings are partly horny, and in folding lap over each other. Butterflies and moths are much alike in appearance but differ in habit. The butterfly works by day and the moth by night. Note the knob on the end of the butterfly's feeler (Fig. 143). The moth has no such knob.

Fig. 140. A Typical Bug
a, adult;
b, side view of sucking
mouth-part Both a and b
are much enlarged

Therefore these do not belong to the true insects

Therefore these do not belong to the true insects

Therefore these do not belong to the true insects

An examination of spiders, mites, and ticks shows eight legs; therefore these do not belong to the true insects, nor do the thousand-legged worms and their relatives.

Fig. 139. The House Fly
a, egg;
b, larva, or maggot;
c, pupa;
(All enlarged)

Fig. 139a. The House Fly
adult male. (Enlarged)

The eyes of insects are especially noticeable

The eyes of insects are especially noticeable

The eyes of insects are especially noticeable

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).

Every one thinks he knows what an insect is

Every one thinks he knows what an insect is

Every one thinks he knows what an insect is

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. Parts of an Insect

Fig. 138. Compound Eye
Of Dragon Fly

Insects in General

Insects in General

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.

Often attacks the unripe fruit on the tree

Often attacks the unripe fruit on the tree

Often attacks the unripe fruit on the tree

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. 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

Peach leaf curl does damage amounting to about $3

Peach leaf curl does damage amounting to about $3

Peach leaf curl does damage amounting to about $3

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.

Club root is a disease of the cabbage

Club root is a disease of the cabbage

Club root is a disease of the cabbage

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. Black Knot

Fig. 133. Moldy Peaches

Fig. 134. Peach Mummies

Watch the potatoes at the next harvest

Watch the potatoes at the next harvest

EXERCISE

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. Club Root

Spraying is the remedy for potato blight

Spraying is the remedy for potato blight

Spraying is the remedy for potato blight

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. Spraying Machine

Fig. 130. Spraying Machine

The blight is another serious disease of the potato

The blight is another serious disease of the potato

The blight is another serious disease of the potato

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

Or enough for thirty gallons of water

Or enough for thirty gallons of water

Or enough for thirty gallons of water

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

123 shows a very scabby potato

123 shows a very scabby potato

123 shows a very scabby 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.
From a scabby potato,
like the one in Fig. 123,
this yield was obtained

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

Mix this with three gallons of water

Mix this with three gallons of water

Mix this with three gallons of water

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. A Scabby Seed Potato

Fig. 124. A Healthy Seed Potato

Do you know of any fields that have been treated for smut

Do you know of any fields that have been treated for smut

Do you know of any fields that have been treated for smut

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?

On plants about an inch long or of the age shown in Fig

On plants about an inch long or of the age shown in Fig

On plants about an inch long or of the age shown in Fig

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

This black dust consists of the spores of a tiny fungous plant

This black dust consists of the spores of a tiny fungous plant

This black dust consists of the spores of a tiny fungous plant

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.

Cut and burn all diseased twigs that you can find

Cut and burn all diseased twigs that you can find

Cut and burn all diseased twigs that you can find

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. Loose Smut
of Oats
The glumes at a
more nearly destroyed
than the glumes at b

Fig. 122. A Crop from Oats
treated with Formalin

EXERCISE

EXERCISE

EXERCISE

EXERCISE

Ask your teacher to show you a case of fire-blight on a pear or apple tree. Can you distinguish between healthy and diseased wood? Cut the twig open lengthwise and see how deep into the wood and how far down the stem the disease extends. Can you tell surely from the outside how far the twig is diseased? Can you find any twig that does not show a distinct line of 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.

Yet our country loses greatly by this disease each year

Yet our country loses greatly by this disease each year

Yet our country loses greatly by this disease each year

A large pear-grower once said that no man with a sharp knife need fear the fire-blight. Yet our country loses greatly by this disease each year.

It may be added that winter pruning tends to make the tree form much new wood and thus favors the disease. Rich soil and fertilizers make it much easier in a similar way for the tree to become a prey to blight.

All The Other Plants in This Field Died. This One Row Lived Because it Could Resist The Cotton Wilt

All The Other Plants in This Field Died. This One Row Lived Because it Could Resist The Cotton Wilt

Fig. 120. Fire-Blight
BacteriaMagnified

When any tree shows blight, every diseased twig on it must be cut off and burned in order to kill the germs, and you must cut low enough on the twig to get all the bacteria. It is best to cut a foot below the blackened portion. If by chance your knife should cut into wood containing the living germs, and then you should cut into healthy wood with the same knife, you yourself would spread the disease. It is therefore best after each cutting to dip your knife into a solution of carbolic acid. This will kill all bacteria clinging to the knife-blade. The surest time to do complete trimming is after the leaves fall in the autumn, as diseased twigs are most easily recognized at that time, but the orchard should be carefully watched in the spring also. If a large limb shows the blight, it is perhaps best to cut the tree entirely down. There is little hope for such a tree.

If harmful bacteria exist in near-by trees

If harmful bacteria exist in near-by trees

If harmful bacteria exist in near-by trees

The bacteria causing fire-blight are readily carried from flower to flower and from twig to twig by insects; therefore to keep these and other bacteria away from your trees you must see to it that all the trees in the neighborhood of your orchard are kept free from mischievous enemies. If harmful bacteria exist in near-by trees, insects will carry them to your orchard. You must therefore watch all the relatives of the pear; namely, the apple, hawthorn, crab, quince, and mountain ash, for any of these trees may harbor the germs.

Fig. 119. A Resistant Variety of Sea Island Cotton

This disease is caused by bacteria

This disease is caused by bacteria

This disease is caused by bacteria

This disease is caused by bacteria, of which you have read in another section. The fire-blight bacteria grow in the juicy part of the stem, between the wood and the bark. This tender, fresh layer (as explained on page 79) is called the cambium, and is the part that breaks away and allows you to slip the bark off when you make your bark whistle in the spring. The growth of new wood takes place in the cambium, and this part of the twig is therefore full of nourishment. If this nourishment is stolen the plant of course soon suffers.

Some Special Plant Diseases

Some Special Plant Diseases

Fire-Blight of the Pear and Apple. You have perhaps heard your father speak of the "fire-blight" of pear and apple trees. This is one of the most injurious and most widely known of fruit diseases. Do you want to know the cause of this disease and how to prevent it?

First, how will you recognize this disease? If the diseased bough at which you are looking has true fire-blight, you will see a blackened twig with withered, blackened leaves. During winter the leaves do not fall from blighted twigs as they do from healthy ones. The leaves wither because of the diseased twig, not because they are themselves diseased. Only rarely does the blight really enter the leaf. Sometimes a sharp line separates the blighted from the healthy part of the twig.

Second you can often kill spores on

Second you can often kill spores on

Second you can often kill spores on

Second, you can often kill spores on seeds before they are planted and thus prevent the development of the fungus (see pp. ).

Third, often the foliage of the plant can be sprayed with a poison that will prevent the germination of the spores (see pp. ).

Fourth, some varieties of plants resist disease much more stoutly than others. We may often select the resistant form to great advantage (see Fig. 119).

Fifth, after big limbs are pruned off, decay often sets in at the wound. This decay may be prevented by coating the cut surface with paint, tar, or some other substance that will not allow spores to enter the wound or to germinate there.

Sixth, it frequently happens that the spore or fungus remains in the soil. This is true in the cotton wilt, and the remedy is so to rotate crops that the diseased land is not used again for this crop until the spores or fungi have died.