Cover crops may be said to be supplementary to tillage. In the previous chapter this function has been discussed. It now remains to point out another important function—that of a green manure crop adding humus and plant food to the soil. Not only do some cover crops add plant food and all humus to the soil, but they tend to conserve these by preventing leaching, especially of nitrates, and they help to render plant food more available by reworking it and leaving it in a form more available for the tree. They sometimes act as a protection against winter injury by holding snow and by their own bulk. They also help to dry out the soil in spring, thus making the land tillable earlier.
There are two great classes of cover or green manure crops, leguminous and non-leguminous. A non-leguminous crop merely adds humus andimproves the physical condition of the soil. In itself it adds no plant food, although it may take up, utilize, and leave behind plant food in a more available form for the tree's use. But in addition to these benefits, leguminous crops actually add to the soil plant food in the form of nitrogen which they have the ability to assimilate from the air by means of bacterial organisms on their roots.
Non-Leguminous Crops.—The most important of the non-leguminous crops are rye, buckwheat, turnips or rape, barley, oats, and millet. The first mentioned are the most commonly used. Also in order of importance the following are the usual leguminous cover and green manure crops to be used: clovers, winter vetch, soy beans, alfalfa, cow peas (first in the South). In order to determine the relative advisability of the use of these various crops let us now look at some of their characteristics and requirements.
Rye is one of the best non-leguminous cover crops, especially in the young orchard, as it does not grow as well in shade as in the open. A particularly strong point about rye is that it grows rapidly quite late in the fall and starts early in the spring. Starting earlier than mostcrops in the spring, it makes a considerable amount of growth before the land is fit to plow. Especially in warmer climates rye should not be sown too early in the fall—not usually before September 1st—because of this too heavy growth. Rye is also adapted to a great variety of soils and hence will often grow where other crops will not do well. About two bushels of seed are required per acre.
Buckwheat is probably about equally as good as rye for an orchard cover crop, although it does not produce quite as much organic matter. It will germinate at almost any season of the year even if it is very dry. It is a great soil improver because of its ability to feed and thrive on soils too poor for other crops, due to its numerous shallow feeding rootlets. It grows rapidly and covers the ground well, but like rye does not thrive as well in shade. Buckwheat should not be used to excess on the heavier types of soil as it is rather hard on the land. One bushel of seed to an acre makes a good seeding.
Turnips or rape often make good pioneer cover or green manure crops. They are great soil improvement crops and it is comparatively easy to secure a good stand of them even indry weather. Sown in late July in the North they will produce a great bulk of humus and add much moisture to the soil, especially if they cover the ground well. Their broad, abundant leaves and high tops also hold the snow well in winter. Cow Horn is the best variety of turnips to use, as it is a large, rank grower. Use one to two pounds of seed to the acre. Rape makes an excellent pasture crop in an orchard both for sheep and hogs, but especially for the former. Eight or nine pounds of seed are necessary to the acre.
Barley, oats, and millet are not as good crops as the foregoing, because, with the possible exception of millet, they make their best growth early in the season. Moreover they take up too much moisture from the soil at a time when the tree most needs this moisture. In fact they are sometimes used for this specific purpose on wet land in too wet seasons. Two to two and one half bushels of oats or barley and one to one and one half bushels of millet to the acre are necessary for a good seeding.
Although weeds can hardly be classified as cover crops, they are often valuable ones. They grow rapidly and rank, making a large bulk of humus, without the expense of seeding. Ifthey are not allowed to go to seed so as to scatter the seed about the farm, they often make the best of cover crops. This necessitates a mowing in September. Weeds are plants out of place, and when these plants are in place they are not necessarily weeds, as they have then become serviceable.
Legumes.—In general, legumes are more valuable as cover and green manure crops than non-leguminous plants, because as a rule they are more rank growers and more deeply rooted, as well as because they add nitrogen to the soil. But it is rather more difficult to secure a good stand of most legumes than it is of the crops previously mentioned for several reasons. As a rule the seeds are smaller and a large seed usually has greater germinating power than a small one. This often means much at the time of the year when the cover crop is sown. Then legumes are more difficult to grow, requiring better soil conditions. Still these should be present in good orchard soils. Drainage must be good, the soil must be at least average in fertility and physical condition, it must not be sour—hence it is often necessary to use lime—and soils frequently require inoculation before they will grow legumes satisfactorily.
Where the clovers grow well they make excellent cover crops as well as green manure crops. The chief difficulty with them is that of obtaining a good stand in a dry midsummer. The mammoth red and the medium red clovers are probably the best of their genus on the heavier soils, while crimson clover is best on sandy soils and where it will grow, on the lighter gravel loams. The latter is especially well adapted to building up run down sandy soils. Although it is somewhat easier to secure a stand of this clover, alsike does not grow rank enough to make a good cover or green manure crop. Most clovers are deep rooted plants and therefore great soil improvers physically as well as being great nitrogen gatherers. The amounts of seed required per acre for the different kinds are about as follows: mammoth fifteen to twenty pounds; red (medium) twelve to fifteen pounds; crimson twelve to fifteen pounds; and alsike ten to twelve pounds.
Where it can be readily and successfully grown alfalfa is really a better cover and green manure crop than the clovers. It is deeper rooted, makes a better top growth, and therefore adds more nitrogen and more humus to the soil than the clovers. It cannotbe recommended for common use, however, as it is so difficult to grow except under favorable conditions. It requires a more fertile soil than clover, a soil with little or no acidity, good drainage, and usually the soil must be inoculated. Only where these conditions prevail can alfalfa be generally recommended.
Vetch is an excellent cover and green manure crop, forming a thick, close mat of herbage which makes a good cover for the soil. It is very quick to start growing and a rapid grower in the spring. It also adds larger quantities of nitrogen. The hairy or winter vetch lives through the hard freezing winters. Summer vetch, although an equally good grower, is killed by freezing. One bushel of seed is required per acre and the seed is expensive, which is the greatest objection to the use of this excellent crop.
Two other less well known and used leguminous crops are well worth trial as cover crops—soy beans in the North and cow peas in the South. Both are great nitrogen gatherers and as they are rank and rapid growers add large quantities of humus to the soil. Under favorable conditions they will cover the ground with a perfect mat of vegetation in a very short time.Being larger seeded, it is considerably easier to obtain a stand on dry soils and in dry seasons than it is of the smaller seeded clovers. It is usually best to sow in drills the ordinary width, seven inches, apart.
Cow peas are universally used as a cover and green manure crop in the South, but they do not thrive so well in the North. One and one half to two bushels of seed are required per acre. In the North the earlier maturing varieties of soy beans are almost equally good. One to one and one half bushels of seed are sown per acre.
Leguminous cover crops are also the best and the cheapest source of nitrogen for the apple orchard, after they are well established. Their use may be overdone, however. Too much nitrogen results in a growth of wood at the expense of fruit buds. To avoid this it is often advisable to use non-leguminous and leguminous crops alternately, when the orchard is making a satisfactory growth. Sometimes also these two kinds of crops, as buckwheat and clover for example, may be combined with good results. When this is done one half the usual amount of seed of each should be used.
Early Plowing.—Many people make thecommon mistake of thinking that a green manure crop must be allowed to grow until late in June in order to secure the maximum amount of growth. There are several reasons why this is not good practice. In the first place cultivation is most essential in the early spring as has been pointed out. Then moisture is better conserved by plowing under the crop early and a better physical condition of the soil secured. Plowing early in the spring warms up the soil and sets plants to work more quickly. Lastly, material rots much more quickly in the early spring when moisture is more abundant, which is very important.
An apple tree is as much a crop as anything grown on the farm and must be so regarded by those who would become successful orchardists. When it is not properly fed and cared for, good yields of fruit may not justly be expected. Especially is this true of an orchard which is being intercropped. But because of the fact that an apple tree is not an annual crop but the product of many years' growth, because its root system is deeper and more widely spread out than those of other crops, and because the amount of plant food removed in a crop of fruit is comparatively small, fertilization is lessimportant than many persons would have us think. It is a fact that where orchards receive good cultivation and a liberal supply of humus commercial fertilizers give but medium results.
Elements of Fertility.—Three elements are necessary for the growth of apple trees, nitrogen, phosphoric acid, and potash. To these lime may be added, although its benefit is indirect rather than direct as a plant food. How badly any of these elements may be needed depends on the soil, its previous treatment, and on the system of management. By learning what are the effects of these elements on the tree and fruit we may determine under what conditions, if any, their use is advisable.
Nitrogen promotes the growth of new wood and leaves, giving the latter a dark green color. In fact the color of the leaves and the amount of the wood growth are usually good indicators of the need of nitrogen. Nitrogen in excess develops over vigorous growth and prevents the maturity of wood and buds. It always has a tendency to delay the maturity of the fruit by keeping it growing late. On many varieties it tends to produce poorly colored fruits.
When trees are making a normal amount of growth in a year—say a foot to three feet ormore—and when the leaves are of good size and a dark green in color, there is little need of nitrogen. But when trees are not growing satisfactorily and the leaves have a sickly yellow color, then the need of nitrogen is evident. On early soils and in long growing seasons nitrogen may be more freely and safely used than under other conditions.
The effect of phosphoric acid and potash on the tree and fruit is much more uncertain. They are supposed to influence the quality and the flavor of the fruit, giving better color and flavor, and this they undoubtedly do to some extent. Potash probably gives the leaves a darker green color. The precise effect of these two elements is at present a subject of much discussion, one set of investigators maintaining after a long and careful investigation that these effects are too small to be worth while, and the other claiming that they have a marked effect in the ways above indicated. The only safe guide is the actual local result. If the fruit is satisfactory in every way it will be of little use to try fertilizers. On the other hand, if it is not, then it will pay to experiment with them. The needs of and the results on different soils are so variable that it is always wise toexperiment on a small scale before using fertilizers extensively.
Stable Manure.—The necessary plant food is best supplied by stable manure applied at the rate of ten loads per acre for a light application to twenty loads per acre for a heavy application. This amounts to a load for from two to five mature trees. Such an application will not only go far toward supplying the necessary nitrogen, phosphoric acid, and potash, but especially if coarse will add considerable humus and improve the physical condition of the soil.
Except on land which washes badly, manure should be applied in the fall and winter. It should not be piled near the trunk of the tree but spread uniformly over the entire surface of the ground. It is particularly important to spread the manure under and beyond the farthest extent of the branches as this is the most important feeding root area of the tree.
Commercial Fertilizers.—Where manure is not available or where it cannot be applied in sufficient amounts, commercial fertilizers may be resorted to, after they have been experimentally tested out. Leguminous cover crops are the best source of nitrogen, as has been indicated, but where these do not grow well,or in seasons when they have for some reason failed, nitrate of soda or dried blood are good substitutes. From two hundred to three hundred pounds of one or the other of these may be applied broadcast in the spring soon after growth is well started and all danger of its being checked by frost or cold weather is past. It is well to apply the nitrate of soda in two applications a few weeks apart, especially on soils which are leachy and in wet seasons, as part of the nitrogen may leach away if all is applied at once. These should be thoroughly worked into the soil with a spring-tooth harrow.
To supply the other two elements, from two hundred to four hundred pounds of treated rock phosphate or basic slag for the phosphoric acid, and the same amount of sulphate of potash for the potash, should be applied at any time in the early part of the season, preferably just before a light rain, and worked into the soil as before. Home-made wood ashes are a good source of both these elements, and especially of the potash. They cannot be purchased economically in any quantity, but on the general farm there could be no better way to utilize the wood ashes made around the place than by applying them two or three bushels to a full grown treeevery year or two. Wood ashes are also a good source of lime, being about one-third calcium oxide. Thus a large amount of available plant food will be supplied to the tree, and where it is needed should result not only in better wood growth but in the formation of vigorous leaf and fruit buds for the following year.
Lime is not usually considered as a fertilizer except on soils actually deficient in it. But it will usually be advisable to apply from one thousand five hundred to two thousand pounds of fresh burned lime or its equivalent, in order to correct any natural soil acidity, to hasten the decay of organic material, to increase the activity of the soil bacteria, and to improve the physical condition of the soil by floculating the soil particles and helping to break up lumpy soils. Lime also helps to liberate plant food by recombining it with certain other elements in the soil. All these effects make a more congenial medium for the leguminous crops to grow in, and it is frequently advisable to use lime for this purpose alone. After this first heavy application about 800 pounds of lime should be applied per acre every four or five years.
It is a common saying among farmers who have grown apples on their farms for many years that there are many more pests to fight than there used to be. How often we have heard a farmer tell of the perfect apples that grew on a certain tree "when he was a boy," before people had generally heard of codling moth, San José scale, apple scab, or other troubles now only too common. "We never sprayed, but the apples were fine," he says. Is this the usual glorification of the mythical past or is it true? In all probability it is a little of both, but it is undoubtedly true that insects and fungous diseases have increased rapidly of late years.
Reasons for Pest Increase.—When there is an abundance of food and conditions are otherwise favorable, any animal or plant will thrive better than when the food supply is scarce and conditions unfavorable. As long as appletrees were scattered and few in number there was not the opportunity for the development of apple pests, but as soon as they became numerous the prosperity of bugs and minute plant parasites was wonderful to see. Another factor which has been at least partly responsible for the great increase in our insect life is that man has upset nature's balance by destroying so many birds, and, by interfering with their natural surroundings, driven them away. Birds are great destroyers of insects, and their presence in the orchard should be encouraged in every possible way. Add to these facts the marvelous fecundity of the insect tribe, and the increase is less remarkable. Loss from these orchard pests has now run up into the millions. It has been estimated that the loss in the United States from wormy apples alone is over $11,000,000 annually. Thus has the necessity for fighting these enemies of good fruit arisen.
In order successfully to combat an insect or a disease it is very necessary to have a somewhat detailed knowledge of its life history and to know its most vulnerable point of attack. It is impossible to work most intelligently and effectively without this knowledge, which should include the several stages of the insect ordisease, the point of attack, the time of making it, and when and with what it can be most easily destroyed. The number of insects and diseases which affect the apple is so great that it is simply out of the question to treat them all in detail here. We have therefore selected nine insects and three diseases as those pests of the apple which are most common and whose effects are usually most serious. The essential facts in their life histories and their vulnerable points will now be pointed out. The method of study may be taken as applicable to any other pests which it may be necessary to combat.
Insect Pests.—Of the many insects which affect either the tree or the fruit of the apple, the nine selected probably inflict the most damage and are the most difficult to control of all those in the Northeastern States. According to their method of attack all insects may be divided into two classes: biting and sucking. Biting insects are those which actually eat parts of the tree, as the leaves or fruit. These are combated by the use of stomach poisons as we shall see in the following chapter. Sucking insects are those which do not eat the tree or fruit directly, but by means of a tubelike proboscis suck the juices or sap from the limbs, leaves orfruit. Of the biting insects the five which we shall discuss are: (1) codling moth, (2) apple maggot, (3) bud moth, (4) cigar case bearer, (5) curculio. The four sucking insects discussed are: (6) San José scale, (7) oyster shell scale, (8) blister mite, and (9) aphis or plant louse.
1.The Codling Moth, the most insidious of all apple pests, is mainly responsible for wormy apples. The adult is a night flying moth with a wing expanse of from one-half to three-quarters of an inch. The moths appear about the time the apple trees are in bloom. Each female is supposed to lay about fifty eggs which are deposited on both the leaves and fruit, but mostly on the calyx end of the young apples. The eggs hatch in about a week and the young larvae or caterpillars begin at once to gnaw their way into the core of the fruit. Three-fourths of them enter the apple through its blow end.
After twenty to thirty days of eating in the apple, during which time they become full grown and about three-quarters of an inch long, they leave the apple, usually through its side. The full grown caterpillar now secretes itself in the crevices in the bark of the tree or inrubbish beneath the tree and spins a tough but slight silken cocoon in which the pupal period is passed. This lasts about a fortnight, when the process is sometimes repeated, so that in the Eastern States there are often two broods each season.
The most vulnerable point in the career of this little animal is when it is entering the fruit. If a fine poison spray covers the surface of the fruit, and especially if it covers the calyx end of the apple inside and out, when the young larvae begin to eat they will surely be killed. It is estimated that birds destroy eighty-five per cent. of the cocoons on the bark of trees.
2.Apple Maggot.—It is fortunate that the apple maggot, often called the railroad worm because of its winding tunnels all through the fruit, is not as serious a pest as the codling moth for it is much more difficult to control with a poison. A two-winged fly appears in early summer and deposits her eggs in a puncture of the skin of the apple. In a few days the eggs hatch and the maggots begin to burrow indiscriminately through the fruit. The full grown larvae are a greenish white in color and about a quarter of an inch long. From the fruit this insect goes to the ground where the pupal stage ispassed in the soil. The next summer the fly again emerges and lays its eggs.
Spraying is not effective against this insect as the poison cannot be placed where it will be eaten by the maggots. The best known remedy is to destroy the fruit which drops to the ground and for this purpose hogs in the orchard are very effective. The distribution of this insect in the orchard is limited and it has shown a marked preference for summer and autumn varieties.
3.The Bud Mothclosely resembles the codling moth in form and size, but differs from it in color and life history. The larvae, after hibernating through the winter, appear as little brown caterpillars about May first or as soon as the buds begin to open, and a week or two later begin their work of destruction. They inflict great damage on the young leaf and fruit buds by feeding on them. When full grown the larvae, cinnamon brown in color with a shining black head, are about one-half inch long. They then roll themselves up in a tube made from a leaf or parts of leaves securely fastened together with silken threads. In this cocoon pupation, which lasts about ten days, takes place. Early in June the moths appear. There is butone brood in the North. These insects can be successfully combated with a poison spray applied early before the buds open.
4.The Cigar Case Bearerwinters in its case attached to a twig. When the buds begin to open in the spring it moves to them, carrying its case with it, and begins to feed on the young and tender buds. By the time the leaves are well open, it has fed a good deal on the tender buds and young leaves and is ready to make a new and larger case. This it does by cutting a leaf to suit and then rolling it up in the form of a cigar, whence its name. In this case the larvae continue feeding about a month, causing much injury to the leaves, although this is not as serious as the mutilation of the young buds in the spring, before the tree is fully leafed out.
About the last of June pupation takes place and in about ten days the moth emerges. The eggs are then layed along the midribs of the leaves and hatch in about fifteen days. The newly hatched larvae become leaf miners during August, and migrate to the branches again in the fall where they pass the winter. These leaf and bud eating insects can be destroyed by applying a poison to the buds before they openand again later to the opening leaf and flower buds.
5.Curculio Beetlespass the winter under leaves and grass. In the spring they feed on the blossoms and the tender leaves. As soon as the young fruits are formed the female deposits her eggs in a puncture made just inside a short, crescent-shaped cut in the little apple. The eggs soon hatch and the young grubs burrow into the fruit to the core where they remain two or three weeks, or until full grown. The larvae then bore their way out of the fruit and drop to the soil where they pupate. The earliest of the beetles to emerge again feed on the fruit. The principal damage from this pest comes from the feeding of the beetles and the work of the larvae, although the latter is not as bad in the apple as in the stone fruits. A poison on the young foliage as soon as the beetles begin to feed is the best method of combating curculio. Jarring the tree is not as practicable with the apple as it is with the plum.
6.The San José Scale, one of our worst apple tree pests, is a sucking insect extracting the juices of the tree from the trunk, limbs or branches, or even from the leaves and fruit when it is very abundant. At first the growthis checked only, but as the insects develop their work finally results in the death of the part, unless they are destroyed. The insect winters in an immature condition on the bark under a grayish, circular, somewhat convex scale about the size of a pinhead. The young, of which a great many broods are produced, are soft bodied but soon form a scale. In the early spring small two-winged insects issue from these scales.
After mating the males die, but the females continue to grow and in about a month begin the production of living young—minute, yellow, oval creatures. These young settle on the bark and push their slender beaks into the plant from which they begin to suck out the sap. In about twelve days the insects molt and in eight to ten more they change to pupae, and in from thirty-three to forty days are themselves bearing young. A single female may give birth to four hundred young in one season and there are several generations in a season. This great prolificacy is what makes the scale so serious a pest.
In fighting it every scale must be destroyed or thousands more are soon born. In order to be able to use a strong enough mixture of limeand sulphur to destroy them by smothering or choking the spray must be applied on the dormant wood in the spring or fall or both. Thoroughness is most essential.
7.The Oyster Shell Scale, although it is essentially the same in its habits and in its methods of sucking the sap from the tree is not as bad a pest as the San José scale because it is less prolific, there being but one brood a year. Still this scale often destroys a branch and sometimes a whole tree. The "lice" winter as eggs under the scale and hatch in late May or early June. After crawling about the bark for two or three days, the young fix their beaks into it and remain fastened there for life, sucking out the sap. By the end of the season they have matured and secreted a scaly covering under which their eggs for the next season's crop winter. A smothering spray like lime and sulphur applied strong when the trees are dormant will practically control this scale. But the young may be destroyed in summer by a contact spray such as tobacco leaf extract or whale oil soap.
8.The Leaf Blister Miteis a small, four-legged animal, so small as hardly to be visible to the naked eye. It passes the winter in thebud scales and as soon as these begin to open in the spring it passes to the tender leaves which it punctures, producing light green or reddish pimples according to the variety of apple. These later develop into galls or blisters of a blackish or reddish brown color and finally result in the destruction of the leaf. Trees are sometimes practically defoliated by this pest, and this at a time when a good foliage is most needed. Inside of the galls eggs are deposited and when the young hatch they burrow in all directions. In October the mites abandon the leaves to hibernate in the bud scales again. A strong contact spray of lime sulphur when the trees are dormant destroys the young mites while they are yet on the bud scales, which is practically the only time when they are vulnerable.
9.Aphides, or plant lice, are of seasonal importance. Although nearly always present, it is only occasionally that they become so numerous as seriously to damage mature apple trees. But they are more often serious pests on young trees where they should be carefully watched. Their presence is determined by the curled and distorted condition of the terminal leaves on the under side of which the green or pinkish lice will be found. Eggs deposited in autumnpass the winter in this condition, hatching in the spring about the time of the beginning of the growth of vegetation. From these winter eggs females are hatched which bear living young, which may also bear living young and so on for several generations until autumn, when eggs are again deposited for the winter stage.
Fortunately weather conditions together with parasitic and predaceous insects hold them more or less in check. Because of the difficulty of getting at the underside of the curled leaves where these lice mostly work they are extremely hard to control. Lime and sulphur when the trees are dormant destroy as many of the eggs as it comes in contact with. A tobacco extract is quite effective as a contact spray in the growing season. The trees must be closely watched and if the lice appear in any considerable number they must be promptly attended to or serious damage is likely to result.
These are by no means all the insect pests which the fruit grower has to combat, but they are usually the most important. Canker worm and tent caterpillars often do great damage in unsprayed orchards, but they are easily controlled by an application of a poison as soonas they appear. The same is true of other caterpillars and leaf eating worms. Apple tree borers are frequently serious, especially in young orchards, where the trees should be regularly "grubbed" and the borers dug out or killed with a piece of wire. They may be prevented to some extent by painting the tree trunks with a heavy lime and sulphur or some gas tar preparation.
Diseases.—Although not as numerous as insects, the diseases which attack the apple inflict great damage and are fully as difficult to control. They are caused by bacteria and by fungi which may be compared to weeds growing on or in the tree instead of the soil. If either of these works within the plant, as is sometimes the case, it must be attacked before it enters. It is very necessary to be thorough in order to control these diseases. Weather conditions influence nearly all of them materially. Of those which attack the apple tree or fruit we have selected three as the most serious and the most necessary for the grower to combat, namely, (1) apple scab, (2) New York apple tree canker, and (3) fire blight. To these should be added in the South and middle latitudes, sooty blotch and bitter rot. Baldwinspot is also frequently serious in some seasons and localities.
(1)The Apple Scab, commonly known among growers as "the fungus," is the most important of our common apple diseases and is most evident on the fruit, although it attacks the leaves as well. In some seasons the fruit is made almost unsalable. This disease lives through the winter on old leaves. In the spring about blossoming time the spores are scattered by the wind and other agencies, and reaching the tender shoots germinate and enter the tissues of the plant. Their development is greatly dependent on the weather. In a season in which there is little fog or continued damp or humid weather, they may not develop at all, but where these conditions are present they frequently become very virulent.
Spraying will be governed by the weather conditions, but the mixture must be applied very promptly as soon as it is evident that it is likely to be necessary and must cover every part of the tree to be effective. The object is to prevent the spores from germinating, the spray being entirely a preventive and in no sense a cure. The disease most frequently first manifests itself on the tender new growth and on theblossoms. Two mixtures have been found to control it, namely, Bordeaux and a weak solution of lime and sulphur. One or other of these should be applied just before the blossoms open, just before they fall, and when necessary two and nine weeks later.
(2)New York Apple Tree Cankeris usually found mainly on the trunks of old trees, but it also affects the smaller branches. Practically every old or uncared for orchard has more or less of this canker, and where it is not checked it eventually destroys the tree. This fungus is the cause of most of the dead wood found in old orchards. The surface of the canker is black and rough and covered with minute black pimples. It lives over winter and spreads from one branch or tree to another. As it most frequently enters a branch through wounds made in pruning, these should be promptly painted over with a heavy lead and oil paint. All diseased parts should be cut out and removed as soon as observed. The value of spraying for this disease is not definitely known, but it is seldom very troublesome in well sprayed and well cared for orchards.
(3)Blightappears on apple trees in three forms, as blossom blight, as twig blight, and asblight cankers. It is a bacterial disease which is distributed by flies, bees, birds, etc., and cannot be controlled by spraying. The bacteria are carried over the winter in cankers on the main limbs and bodies of the trees, oozing out in a sticky mass in the spring. These cankers should be cut out with a sharp knife cutting well into the healthy bark and then washing the wound with corrosive sublimate, one part to one thousand of water. Cutting out and destroying are also the chief remedies to be used when the blight appears in the twigs and blossoms. It is not usually as serious on apples as on pears. Some varieties, like Alexander, are more subject to it than others.
The spraying of fruit trees in the United States is of comparatively recent origin, having been a general commercial practice for less than two decades. It involves the principle of applying with force and in the form of a fine rain or mist, water in which a poison or a substance which kills by contact is suspended. The first application of the principle was against chewing insects with hellebore. Pure arsenic was early used and soon led to the use of other arsenicals.
Our greatest fungicide, Bordeaux mixture, was discovered by accident in 1882 when it was found to control mildew in France. Up until about five years ago Bordeaux mixture as the fungicide and paris green as the poison were almost universally used. Within the last few years, however, there have been developed two substitutes which, although known and used to some extent for twenty years, have onlyrecently come into such general use as practically to replace the old sprays. These are lime and sulphur as the fungicide and partial insecticide and arsenate of lead as a partial insecticide.
The necessity for and the advisability of spraying have already been pointed out. There is an increasing demand for fine fruit the supplying of which is possible only with thorough spraying. In the humid East especially the competition of more progressive sections in the West is demanding more and better spraying. There is no cure-all in this process. It does not make a tree more fruitful except as it improves its general health, but it does bring a larger percentage of the fruit to perfection. Certain knowledge is fundamental; the grower must know what he is spraying for, when and with what to combat it and how to accomplish the desired result most effectively.
Spraying is an insurance against anticipated troubles with the fruit, and the best and most successful growers are those most completely insured. It has many general advantages also. It stimulates the grower to a greater interest in his business because of the extra knowledge and skill required. It compels thoroughness. It necessitates spending money, therefore areturn is looked for. To be sure, it is only one of the operations necessary to success, but it enables us to grow a quality of fruit which we could not obtain without it.
Spray Materialsare conveniently divided into two classes, insecticides and fungicides. An insecticide is a poison by which the insect is killed either directly by eating it, or indirectly by the caustic, smothering, or stifling effects resulting from closing its breathing pores. Direct poisons are used for insects which eat some part of the tree or fruit and are called stomach poisons. Sprays which kill indirectly are used for insects which suck the sap or juice from the tree or fruit and are called contact sprays. Arsenical compounds have supplanted practically all other substances used to combat external biting insects. Two stomach poisons are commonly used, namely, arsenate of lead and paris green, but the former is rapidly replacing the latter.
Arsenate of Leadis prepared by mixing three parts of crystallized arsenate of soda with seven parts of crystallized white sugar (acetate) of lead in water, but it will not as a rule pay the grower to mix his own material, as arsenate of lead can be purchased in convenientcommercial form at a reasonable price. The preparation on the market is a finely pulverized precipitate in two forms, one a powder and the other a paste. These are probably about equally good and are readily kept suspended in water. Less free arsenic is contained in this form than in any other compound of arsenic, making it safer to use, especially in heavy applications. Arsenate of lead may be used without danger of burning the foliage as strong as five or six pounds to fifty gallons of water, but three pounds is the usual and a sufficient amount for the control of any apple insect for which it is efficacious.
Paris Greenis being rapidly displaced by arsenate of lead for several reasons. It is a compound of white arsenic, copper oxide, and acetic acid. The commercial form is a crystal which in suspension settles rapidly, a serious fault. It is more soluble than arsenate of lead and hence there is greater danger of burning the foliage with it. Moreover, it costs from twenty to twenty-five cents a pound, and the arsenate of lead can be purchased for from eight to ten cents a pound.
The amount which it is safe to use in fifty gallons of water is from one-half to three-quarters of a pound. When paris green is usedalone as a poison lime should be added. Both these arsenicals should be thoroughly wet up by stirring in a smaller receptacle before they are put into the spray tank, in order to get them in as complete suspension as possible. They may be used in the same mixture with Bordeaux or lime sulphur.
Contact Sprays.—Four compounds are used as contact sprays in combating sucking insects, namely, lime sulphur, soaps such as whale oil soap, kerosene emulsion, and tobacco extract. Of these lime sulphur is the most used and for winter spraying is probably the best. This preparation is made by boiling together for one hour or until they unite, twenty pounds of quick lime, fifteen pounds of flower of sulphur, and fifty gallons of water. Although the home made mixture is much cheaper than the commercial form which may be purchased on the market, many people prefer the latter because of the inconvenience and trouble of preparing the mixture, although there is nothing difficult about it.
This contact spray is used chiefly for the San José scale and the blister mite, and in order to control these must be applied strong on the dormant wood. The strength necessary will varyfrom one part of the mixture above mentioned or of the commercial preparation, to from seven to ten parts of water, according to the density test of the material, which should be around twenty-eight per cent. Beaumé (a scale for measuring the density of a liquid) for home made, and thirty-two per cent. for the commercial mixture.
Any good soap is effective in destroying soft bodied insects such as plant lice. The fish oil soaps, although variable in composition, are often valuable, especially the one known in the trade as whale oil soap. This soap dissolved in water by boiling at the rate of two pounds of soap to one gallon of water, makes a good winter spray for scale but should be applied before it gets cold as it is then apt to become gelatinous. For a summer contact spray against lice, one pound of soap to seven gallons of water is strong enough to be effective. It is objectionable because of its odor and because it is disagreeable to make and handle. Lime sulphur is to be preferred as a winter spray, but the soap spray is often necessary and valuable for summer sucking insects.
Kerosene emulsion was formerly more commonly used than now against the scale and plantlice. It is a mixture of one-half pound of soap and two gallons of kerosene in one gallon of water—preferably in hot water. For dormant trees one gallon of this mixture should be diluted with six gallons of water. While this spray is effective it is no more so than lime-sulphur and is quite difficult and disagreeable to handle. As a summer spray, however, it is often necessary. Several preparations of petroleum known as the miscible oils are sometimes used. Their use is the same as that of lime-sulphur and they are not as good.
Within the last few years a tobacco concoction known as black leaf tobacco extract (nicotine sulphate) has come into quite common use. It can be purchased commercially under various brand names, and should be diluted according to its strength, but usually about one part to fifty of water. It may be made by boiling one pound of good tobacco stems in two gallons of water for one-half-hour. Objections to it are that it evaporates very quickly, although it is supposed to be non-volatile, and that it is expensive, but it is very convenient to use, can be readily mixed with other summer sprays, and is very effective against plant lice and mites.
Bordeaux Mixture.Fungicides aremixtures of chemical compounds made up for the purpose of controlling plant diseases caused by a class of plant weeds known as fungi. There are three commonly well known and used fungicides, Bordeaux mixture, commercial lime sulphur, and the self-boiled lime-sulphur. The Bordeaux mixture is the best all-around fungicide known. It is a mixture of three pounds of copper sulphate (blue vitriol or bluestone) with three or more pounds of fresh burned stone lime in fifty gallons of water. The two compounds should be put together as fruit growers say "with water between," that is each should be diluted with the water separately before the two are mixed.
The best plan is to have stock mixtures of each in barrels, fifty gallon cider or vinegar barrels making good receptacles for the purpose. Place the bluestone in an old fertilizer or meal sack and suspend it about midway in the barrel of water. In a few hours it will all be dissolved and will remain in suspension for some length of time very well. If say fifty pounds of the copper sulphate are dissolved in fifty gallons of water, each gallon of water will contain one pound of the bluestone, which makes a very convenientway to measure it. So also fifty pounds of fresh burned stone lime should be placed in a barrel—in this case in the bottom of the barrel rather than in a sack—just covered with water and allowed to slake, more water being added as required up to fifty gallons. If too much water is added to the lime at the first it will be "drowned" and its slaking checked. These two stock mixtures, each gallon containing one pound of the copper sulphate or one pound of the lime, are then mixed together.
It is well to fill the tank about half full of water, then put in the required amount of the copper sulphate, and after stirring well add the lime milk. It is a good plan to add an excess of lime as it minimizes the danger of burning and aids the mixture in sticking to the leaves well. If one is sure that he has at least as much lime, or an excess of lime, it will not be necessary to test the mixture, but if he is not, a simple test may be made with ferro-cyanide of potassium, obtained at a drug store. A few drops of this mixture will disappear if the lime is equal or in excess of the copper sulphate, that is, it will be neutralized, but if it is not, they will remain a bright purplish red. Bordeaux mixture is used in strengths varying from three tofive pounds each of bluestone and lime in fifty gallons of water, but the former is usually sufficient.
Lime-Sulphur.—The more important fungicides, the commercial lime sulphur and the self-boiled lime-sulphur, are practically superseding Bordeaux as a fungicide, not because they are necessarily better, but because there is frequently much burning of the foliage and russeting of the fruit from the use of the Bordeaux. This is unfortunate as the latter is a rather more effective fungicide as well as more convenient and pleasant to use. The self-boiled lime sulphur is a combination of lime and sulphur which is boiled by the heat of the slaking lime alone, and makes a pretty good substitute for the Bordeaux when it injures foliage or fruit. This preparation of lime and sulphur differs from the commercial form used as a winter wash in that it is wholly a mechanical mixture and not partly chemical like the latter. It may therefore be used on the foliage in summer at a greater strength, there being only a very small percentage of sulphur in solution when the mixture is properly made.
Equal amounts of lime and sulphur are used, these being from eight to ten pounds each tofifty gallons of water. The mixture is best prepared in larger quantities so as to get heat enough from the slaking lime to produce a violent boiling for a few minutes. First, place say forty pounds of lime in a barrel and pour on just water enough to start it slaking nicely—about a gallon to each three or four pounds of lime is usually sufficient. Then add the sulphur and enough more water to slake the paste, keeping it well stirred meanwhile. The violent boiling of the lime in slaking will cook the mixture in from five to fifteen minutes, depending on the quality of the lime and how fast it is slaked. Just as soon as the violent boiling is over add enough cold water to stop all action. If this is not done, some sulphur will unite with the lime and burning may be the result.
This self-boiled mixture is entirely harmless to apple foliage and even appears to have a stimulating effect upon it. Against the apple scab, however, it is not as effective as the boiled wash, or the commercial preparations. For this disease a strength of from one to thirty to one to forty (that is about one and one-half gallons of the prepared mixture testing 31 to 33 Beaumé to fifty gallons of water) of the commercial lime-sulphur is most effective.
Spray Pumps.—The application of the foregoing spray mixtures is fully as important as the sprays themselves, for on the right application at the right time depends the efficacy of the spray. For this purpose a considerable amount of special machinery has been devised. Lack of space prevents us from going into much detail on this question, so we must be content with merely outlining the different types of machines and mentioning their accessories. Sprays are forced through single, double or triple acting pumps, either by hand or power. The three types of power available are traction, compressed air, and gasoline, the last being the most used. Steam power is practically obsolete.
The knapsack is the simplest type of hand pump, but it is of no practical use in the mature apple orchard. For small orchards and small trees several types of hand pumps are quite effective. The lever type of pump, where the handle is pushed from and pulled toward the operator, probably gives the most power with the least tiring effect, because it enables one to use the weight of the body to some extent. It is best not to have the pump attached to the spray barrel or tank, but set on a movable base of itsown, as then it can be used for any one of a number of barrels. Such an outfit may be obtained for from twenty-five to forty dollars.
It is well to buy a standard make of pump, preferably from a nearby dealer, so that repairs may be readily secured. For all orchards up to three or four acres in size, and for larger orchards where the trees are not over twelve or fifteen feet in height, this kind of spray rig is the most practicable and advisable, when the expense is taken into consideration. This applies especially to the general farm.
The power of a traction sprayer is developed from the wheels. There is much discussion as to whether sufficient power to throw an effective spray can be supplied by this method. By accumulating considerable pressure by extra driving at the ends of the rows and then skipping every other tree in order to keep up the pressure, going over the rows twice, a very satisfactory pressure can be obtained for trees which are not too large. The argument for this type of machine, and it is especially applicable on the general farm, is that it can be used for other spraying on the farm as well as for the apple orchard, especially for potatoes and small fruits. It is a comparatively cheap type ofpower, particularly when it can be used for several purposes.
The compressed air gas sprayer comes next in point of simplicity and cost for a power sprayer. Its most economic use is found where orcharding is carried on extensively enough to pay to compress the air or gas right in the orchard. This is of course impracticable on the general farm. Therefore the air or gas must be purchased and shipped to the farm in steel tubes. This often causes delay at critical times and is rather expensive. Moreover, the gas is open to the objection of interfering with the lime-sulphur compound by precipitating some of the sulphur.
The gasoline engine is the most useful and popular type of power for the orchard sprayer, as well as for general use on the farm. Many makes are now so perfected that they give little or no trouble. One and a half or two horsepower are fully sufficient for spraying, but most farmers prefer from three to five horsepower in order to be able to use the engine more for other purposes. The latter power is open to objection for spraying purposes on account of its weight, as especially in early spring it is very difficult to haul so heavy a rig over the softground. Such an outfit is also rather expensive. Standard makes of gasoline engines of sufficient power for spraying cost from $75.00 to $150.00 according to horsepower and efficiency. For very large trees, for mature orchards, and for all orchards larger than four or five acres, the gasoline engine is the best source of power for spraying, particularly where it can be used for other purposes on the farm.
A double acting or two cylinder pump is most desirable. If there is plenty of power a triplex or three cylinder pump is still better. The requirements of a good pump are: sufficient power for the work desired of it; strong but not too heavy; fewest possible number of parts consistent with efficiency; brass parts and valves; and a good sized air chamber. A number of standard makes of pumps answer these conditions very well. Pumps should always be washed out with clean water when the operator is through with them and the metal parts coated with vaseline. Never leave water in a pump chamber or in the engine jacket in cold weather.
The ordinary hand pump and barrel give satisfactory use when placed on a wagon, unless the trees are very high. But for large orchards, high trees, and where larger tanks and powerpumps are used it is desirable to have a special truck for the outfit. The front wheel should be made low so as to turn under the tank to enable the driver to make short turns around the trees. A tower is desirable where high old trees are to be sprayed. This should be substantial but as small as is consistent with the purpose so as not to catch on the limbs and make it difficult to get close up around the trees. The height of the platform must be regulated by the need and by the roughness of the ground. On steep side hills the wagon body on which the tank rests should be underslung.
In order to get as near to the work as possible get a long hose—from twenty to thirty feet according to circumstances. The best quality, three to five ply, is none too good. Hose should be three-eighths to one-half inch in diameter, one inch being too heavy. Extension rods are a practical necessity. They should be ten to twelve feet long and made of bamboo lined with brass, that is, as light as possible. Nozzles are very important in thorough and effective spraying. There is no best nozzle, nor one with which all the work can be done.
Several things should be considered inselecting a nozzle. First of all, it must be of convenient form so as not to catch in trees and so constructed that it will not clog easily. Second, for apple trees it should have good capacity and deliver as spreading a spray as possible. Third, the nature of the spray is very important. Insecticides should usually be applied with force in a comparatively coarse driving spray, but fungicides should be applied in a fine mist or fog so that they will settle on every part of the tree. Therein lies the difficulty of applying insecticides and fungicides together.
Time of Spraying.—Fortunately it is not necessary to make a separate application for each insect and disease, but they may be treated together to some extent. In most cases expediency demands that the arsenicals be used with the fungicides. Many growers are finding the most satisfactory results, however, from applying the arsenical spray separately, just after the blossoms fall, because of the physical impossibility of properly applying the two sprays—the driving and the mist spray—together. For most practical purposes on the general farm, three sprayings are necessary in order to secure clean fruit and four, sometimes five, are oftenadvisable. These may be summarized as follows: