THE BLIGHT IN THE PEAR-TREE.[18]ITS CAUSE AND A REMEDY FOR IT.Theyear 1844 will long be remembered for the extensive ravages of that disease hitherto denominatedfire-blight. Beginning at the Atlantic coast, we have heard of it in Pennsylvania, Maryland, Virginia, Ohio, Kentucky, Indiana, and as far as Tennessee; and it is probable that it has been felt in every fruit-growing State in the Union where the season of 1843 was the same as that west of the Alleghany range, namely, cold in spring, dry throughout the summer, and a wet and warm fall, with early and sudden winter.In Indiana, and Ohio theblighthas prevailed to such an extent as to spread dismay among cultivators; destroying entire collections—taking half the trees in large orchards—affecting both young and old trees, whether grafted or seedings in soils of every kind. Many have seen the labor and fond hope of years cut off, in one season, by an invisible destroyer, against which none could guard; because, in the conflicting opinions, none were certain whether the disease was atmospheric, insect or chemical.I shall now proceed to describe that blight known in the western States (without pretending to identify it with the blight known in New York and New England), to examine the theories proposed for its causation, and to present what now seems to me the true cause.I.Description.—Although the signs of it, as will appear in the sequel, may be detected long before the leaves put out in the spring, yet its full effects do not begin to appear until May, or if the spring be backward, until June. On the wood of the last year will be found a point where thebark is either dead and dry, or else at the same point the bark will be puffed, softened, or sappy with thickened sap—these two appearances indicating only different degrees of the same blight. Wherever the bark is dead and dry, the limb will flourish above it, make new wood, ripen its fruit, but perish the ensuing winter. In the other case, as soon as the circulation of the sap becomes active, the point described shows signs of disease, the leaf turns to a darker brown than is natural to its ordinary decay, being nearly black, and the wood perishes.The disease, at first, blights the terminal portions of the branch; but the affection spreads gradually downward, and sometimes affects the whole trunk. The time from the first appearance of the blight to that in which any affected part dies, is various; sometimes two or three weeks—sometimes a day only; and sometimes, but rarely, even a few hours consummate the disease.On dissecting the branch, the wood is of a dirty, brownish, yellow color; the sap thick and unctuous, of a sour disagreeable odor, like that of a fermented watermelon, on the tops of potato vines after they have been frosted. In still, moist days, where the blight is extensive in an orchard, this odor fills the air, and is disagreeably perceptible at some distance from the trees.Sometimes the bark bursts, the sap exudes, and runs down, turning black; and its acridity will destroy vegetation on which it may drop, and shoots, at a distance from the trunk, upon which the rain washes this ichor, will soon perish. When we come to treat of thecauseof this disease, it will be important to remember this malignancy of the fluids.We are carefully to distinguish these appearances, peculiar to what I suppose ought to be calledwinter-blight, from another and asummer-blight. In this last, the leaf is affected at first in spots; gradually the whole leaf turns russet color and drops. Along the wood may be seen the hardenedtrail as of a slimy insect, of an ash color. Thewoodsuffers very little by this summer-blight, and sometimes none. The winter-blight is found on almost all kinds of trees. This summer it has affected the apple, the pear, the peach, the quince, the English hawthorn, privet, black birch, Spanish chestnut, elder, and calycanthus. I enumerate the most of these kinds on the authority of J. H. James, of Urbana, Ohio, and C. W. Elliott, of Cincinnati, having observed it myself only on fruit-trees.II.Theories.—A variety of theories exist as to the causes of this disease. Some are mere imaginations; some are only ingenious; and some so near to what I suppose to be the truth, that it is hardly possible to imagine how the discovery was not made.The injury is done in the fall, but is not seen till spring or summer, or even the next fall. Thus, six months or a year intervene between thecauseand theeffect—a sufficient reason for the difficulty of detecting the origin of the evil.1. Some have alleged that the rays of the sun, passing through vapors which arise about the trees, concentrate upon the branches, and destroy them by the literal energy of fire. Were this true, the young and tender shoots would suffer first and most; all pear-trees would suffer alike; moist and hot summers would be affected with blight; herbaceous plants would suffer more than ligneous: all of which results are contrary to facts.2. Some have supposed the soil to contain deleterious substances, or to be wanting in properties necessary to health. But in either case such a cause of the blight appears untrue, when we consider that trees suffer in all soils, rich or poor; that, in the same soil, one tree is blighted and the next tree escapes; that they will flourish for twenty years and then blight; that a tree partially diseased recovers, and thrives for ten or more years without recurrence of blight.3. It has been attributed to violent and sudden changesof temperature in the air and of moisture in the earth; to sudden change from sward to high tillage; and the result is stated to be an “overplus” of sap, or a “surfeit.” All these causes occur every year; but the blight does not every year follow them. Changes of temperature, and violent changes in the condition of the soil, may bealliedwith the true cause. But whenonlythese things exist, no blight follows.4. Others have attributed the disease to over-stimulation by high manuring, or constant tillage; and it has been said that covering the roots with stones and rubbish, or laying the orchard down to grass, would prevent the evil. Facts warrant no such conclusions. Pear-trees in Gibson County, Indiana, on a clay soil, with blue slaty subsoil, were affected this year more severely than any of which we have heard. Pears in southern parts of this State, on red clay, where the ground had long been neglected, suffered as much as along the rich bottom lands of the Wabash about Vincennes. If there was any difference it was in favor of the richest land. About Mooresville, Morgan County, Indiana, pears have been generally affected, and those in grass landsas muchas those in open soils. Aside from these facts, it is well known that pear-trees do not blight in those seasons when they make the rankest growth more than in others. They will thrive rampantly for years, no evil arising from their luxuriance, and then suddenly die of blight.5. It has been supposed by a few to be the effect ofage, the disease beginning on old varieties, and propagated upon new varieties by contagion. Were this the true cause, we should expect it to be most frequently developed in those pear regions where old varieties most abound. But this disease seems to be so little known in England, that Loudon, in his elaborateEncyclopedia of Gardening, does not even mention it. Mr. Manning’s statement will be given further on, to the same purport.6. Insect theory: The confidence with which eastern cultivators pronounce the cause to be aninsect, has in part served to cover up singular discrepancies in the separate statements in respect to the ravages, and even the species of this destroyer. TheGenesee Farmerof July, 1843, says, “the cause of the disease was for many years a matter of dispute, and is so still by some persons; but the majority are now fully convinced that it is the work of an insect (scolytus pyri).” T. W. Harris, in his work on insects, speaks of the minuteness and obscure habits of this insect, as “reasons why it has eluded the researches of those persons who disbelieve in its existence as the cause of the blasting of the limbs of thepear-tree.” Dr. Harris evidently supposed, until so late as 1843, that this insect infested only thepear-tree; for he says, “the discovery of the blight-beetle in the limbs of the apple-tree, is a new fact in natural history; but it is easily accounted for, because this tree belongs not only to the same natural group, but also to the same genus as the pear-tree. It is not, therefore, surprising, that both the pear and the apple-tree should occasionally be attacked by the same insect.” [See an article in theMassachusetts Ploughman, summer of 1843, quoted inGenesee Farmer, July, 1843.]This insect is said to eat through thealburnum, the hard wood, and even a part of the pith, and to destroy the branch by separation of part from part, as a saw would. On these facts, which there is no room to question, we make two remarks.1st. That the blight thus produced islimited, and probably sectional or local. No account has met my eye which leads me to suppose that any considerable injury has been done by it. Mr. Manning, of Salem,Mass., in the second edition of his “Book of Flowers,” states that he has never “had any trees affected by it”—the blight. Yet his garden and nursery has existed for twenty years, and contained immense numbers of trees.2d. It is very plain that neither Mr. Lowell, originally, nor Dr. Harris, nor any who describe the blight as caused by the blight-beetle, had any notion of that disease which passes by the same name in the middle and western States. The blight of thescolytus pyriis a meregirdlingof the branches—a mechanical separation of parts; and no mention is made of the most striking facts incident to the great blight—the viscid unctuous sap; the bursting of the bark, through which it issues; and its poisonous effects on the young shoots upon which it drops.We do not doubt the insect-blight; but we are sure that it is notourblight. We feel very confident, also, that this blight, which from its devastations may be called the great blight, has been felt in New England, in connection with the insect-blight, and confounded with it, and the effects of two different causes happening to appear in conjunction, have been attributed to one, and the least influential cause. The writer in Fessenden’sAmerican Gardener(Mr. Lowell?) says of the blight, “it is sometimes so rapid in its progress, that in a few hours from its first appearance the whole tree will appear to be mortally diseased.” This is not insect-blight; for did the blight-beetle eat sosuddenlyaround the wholetrunk? Now here is a striking appearance of the great blight, confounded with the minor blight, as we think will appear in the sequel.This theory has stood in the way of a discovery of the true cause of the great blight; for every cultivator has gone in search of insects; they have been found in great plenty, and in great variety of species, and their harmless presence accused with all the mischief of the season. A writer in theFarmer’s Advocate, Jamestown,N. C., discerned the fire-blight, and traced it to “small,red, pellucid insects, briskly moving from place to place on the branches.” This is not thescolytus pyriofProf.Peck and Dr. Harris.Dr. Mosher, of Cincinnati, in a letter published in theFarmer and Gardenerfor June, 1844, describes a thirdinsect—“very minute brown-colored aphides, snugly secreted in the axilla of every leaf on several small branches; … most of them were busily engaged with their proboscis inserted through the tender cuticle of this part of thepetioleof the leaf, feasting upon thevital juicesof the tree. The leaves being thus deprived of the necessary sap for nourishment and elaboration soon perished, … while all that part of the branch and trunk below, dependent upon the elaborated sap of the deadened leaves above, shrunk, turned black, and dried up,”p.261.Lindley, in his work onHorticulture,p.42-46, has detailed experiments illustrating vegetableperspiration, from which we may form an idea of the amount of fluid which these “very-minute brown-colored aphides” would have to drink. A sunflower, three and a half feet high, perspired in a very warm day thirty ounces—nearly two pounds; on another day, twenty ounces. Taking the old rule, “a pint a pound,” nearly a quart of fluid was exhaled by a sunflower in twelve hours; and the vessels were still inflated with a fresh supply drawn from the roots. Admitting that the leaves of a fruit-tree have a less current of sap than a sunflower or a grape-vine, yet in the months of May and June, the amount of sap to be exhausted by these very minute brown aphides, would be so great, that if they drank it so suddenly as to cause a tree to die in a day, they would surely augment in bulk enough to be discovered without a lens. If some one had accounted for the low water in the Mississippi, in the summer of 1843, by saying that buffaloes had drank up all the upper Missouri, and cut off the supply, we should be at a loss which most to pity, the faith of the narrator, or the probable condition of the buffaloes after their feat of imbibition.But the most curious resultsfollowthese feats of suction. The limbs and trunkbelowshrink and turn black, for want of that elaborated sap extracted by the aphides. And yet every year we perform artificially this very operation inringingordecorticationof branches, for the purpose of accelerating maturation or improving the fruit. Every year thesawtakes off a third, a half, and sometimes more, of a living tree; and the effect is to produce new shoots, not death. Is an operation which can be safely performed by man,deadlywhen performed by an insect? Dr. Masher did not detect the insects without extreme search, and then only in colonies, on healthy branches. Do whole trees wither in a day by the mere suction of such insects? Had they been supposed topoisonthe fluids, the theory would be less exceptionable, since poisons in minute quantities may be very malignant.While we admit a limited mischief of insects, they can never be the cause of the prevalent blight of the middle and western States—such a blight as prevailed in and around Cincinnati in the summer of 1844—nor of that blight which prevailed in 1832. Theblight-beetle, after most careful search and dissection, has not been found, nor any trace or passage of it. Dr. Mosher’s insect may be set aside without further remark.I think that further observation will confirm the following conclusions:1. Insects are frequently found feeding in various ways upon blighted trees, or on trees which afterward become so.2. Trees are fatally blighted on which no insects are discerned feeding—neither aphides norscolytus pyri.3. Multitudes of trees have such insects on them as are in other cases supposed to cause the blight, without a sign of blight following. This has been the case in our own garden.III.Cause of the Blight.—The Indiana Horticultural Society, early in the summer of 1844, appointed a committee to collect and investigate facts on the Fire-Blight. While serving on this committee, and inquiring in all the pear-growing regions, we learned that Reuben Reagan, of Putnam County, Ind., was in possession of much information, andsupposed himself to have discovered the cause of this evil; and to him we are indebted for a first suggestion of the cause. Mr. Reagan has for more than twelve years past suspected that this disease originated in the fall previous to the summer on which it declares itself. During the last winter Mr. Reagan predicted the blight, and in his pear-orchards he marked the trees that would suffer, and pointed to the spot which would be the seat of the disease; and his prognostications were strictly verified. After gathering from him all the information which a limited time would allow, we obtained from Aaron Alldredge, of Indianapolis, a nurseryman of great skill, and possessed of careful, cautious habits of observation, much corroborative information; and particularly a tabular account of the blight for nine years past in his nursery and orchard.The spring of 1843 opened early, but cold and wet, until the last of May. The summer was both dry and cool, and trees made very little growth of new wood. Toward autumn, however, the drought ceased, copious rains saturated the ground, and warm weather started all trees into vigorous, though late, growth. At this time, while we hoped for a long fall and a late winter, on the contrary we were surprised by an early and sudden winter, and with unusual severity at the very beginning. In the West, much corn was ruined and more damaged; and hundreds of bushels of apples were caught on the trees and spoiled—one cultivator alone losing five hundred bushels. Caught in this early winter, what was the condition of fruit-trees? They were making rapid growth, every part in a state of excitement, the wood unripe, the passages of ascent and descent impleted with sap. In this condition, the fluids were suddenly frozen—the growth instantly checked; and the whole tree, from a state of great excitability, was, by one shock, rudely forced into a state of rest. Warm suns, for a time, followed severe nights. What would be the effect of this freezing and sudden thawing upon the fluids andtheir vessels? We have been able to find so little written upon vegetable morbid anatomy (probably from the want of access to books), that we can give but an imperfect account of the derangement produced upon the circulating fluids by congelation. We cannot state the specific changes produced by cold upon the ascending sap, or on the cambium, nor upon the elaborated descending current. There is reason to suppose that the two latter only suffer, and probably only the last. That freezing and thawing decompose the coloring matter of plants is known; but what other decomposition, if any, is effected, we know not. The effect of congelation upon the descending sap of pear and apple-trees, is to turn it to a viscid, unctuous state. It assumes a reddish brown color; becomes black by exposure to the air; is poisonous to vegetables even when applied upon the leaf. Whether in some measure this follows all degrees of congelation, or only under certain conditions, we have no means of knowing.The effect of freezing and thawing upon the tissues and sap-vessels is better known. Congelation is accompanied with expansion; the tender vessels are either burst or lacerated; the excitability of the parts is impaired or destroyed; the air is expelled from the aëriferous cavities, and forced into the passages for fluids; and lastly, the tubes for the conveyance of fluids are obstructing by a thickening of their sides.[19]The fruit-trees, in the fall of 1843, were then brought into a morbid state—the sap thickened and diseased; the passages lacerated, obstructed, and probably, in many instances burst. The sap elaborated, and now passing down in an injured state, would descend slowly, by reason of its inspissation, the torpidity of the parts, and the injured condition of the vessels. The grosser parts, naturally the most sluggish, would tend to lodge and gradually collect at the junction of fruit-spurs, the forks of branches,or wherever the condition of the sap-vessels favored a lodgment. In some cases the passages are wholly obstructed; in others, only in part.At length the spring approaches. In early pruning, the cultivator will find, in those trees which will ere long develop blight, that the knife is followed by an unctuous sap, and that the liber is of a greenish yellow color. These will be the first signs, and the practised eye may detect them long before a leaf is put forth.When the season is advanced sufficiently to excite the tree to action, the sap will, as usual, ascend by the alburnum, which has probably been but little injured; the leaf puts out, and no outward sign of disease appears; nor will it appear until the leaf prepares the downward current. May, June and July, are the months when the growth is most rapid, and when the tree requires the most elaborate sap; and in these months the blight is fully developed. When the descending fluid reaches the point where, in the previous fall, a total obstruction had taken place, it is as effectually stopped as if the branch were girdled. For the sap which had lodged there would, by the winds and sun, be entirely dried. This would not be the case if the sap was good and the vitality of the wood unimpaired; but where the sap and vessels are both diseased, the sun affects the branch on the tree just as it would if severed and lying on the ground. There will, therefore, be found on the tree, branches with spots where the bark is dead and shrunk away below the level of the surrounding bark; and at these points the current downward is wholly stopped. Only theoutwardpart, however, is dead, while thealburnum, or sap-wood, is but partially injured. Through the alburnum, then, the sap from the roots passes up, enters the leaf, and men are astonished to see a branch, seemingly dead in the middle, growing thriftily at its extremity. No insect-theory can account for this case; yet it is perfectly plain and simple when we consider that there are two currentsof sap, one of which may be destroyed, and the other for alimited timego on. The blight, under this aspect, is nothing butringingordecortication, effected by diseased sap, destroying the parts in which it lodges, and then itself drying up. The branch will grow, fruit will set, and frequently become larger and finer flavored than usual.But in a second class of cases, the downward current comes to a point where the diseased sap had effected only a partial lodgment. The vitality of the neighboring parts was preserved, and the diseased fluids have been undried by wind or sun, and remain more or less inspissated. The descending current meets and takes up more or less of this diseased matter, according to the particular condition of the sap. Wherever the elaborated sap passes, after touching this diseased region, it will carry its poison along with it down the trunk, and, by the lateral vessels, in toward the pith. We may suppose that a violence which would destroy the health of the outer parts, would, to some degree, rupture the inner sap-vessels. By this, or by some unknown way, the diseased sap is taken into the inner,[20]upward current, and goes into the general circulation. If it be in a diluted state, or in small quantities, languor and decline will be the result; if in large quantities, and concentrated, the branch will die suddenly, and the odor of it will be that of frost-bitten vegetation. All the different degrees of mortality result from the quantity and quality of the diseased sap which is taken into circulation. In conclusion, then, where, in one class of cases, the feculent matter was, in the fall, so virulent as to destroy the parts where it lodged, and was then dried by exposure to wind and sun, the branch above will live, even through the summer, but perish the next winter; and the spring afterward, standing bare amid green branches, the cultivator may suppose the branch tohave blighted that spring, although the cause of death was seated eighteen months before. When, in the other class of cases, the diseased sap is less virulent in the fall, but probably growing worse through the spring, a worse blight ensues, and a more sudden mortality.We will mention some proofs of the truth of this explanation.1. The two great blight years throughout the region of Indianapolis, 1832 and 1844, were preceded by a summer and fall such as we have described. In the autumns of both 1831 and 1843, the orchards were overtaken by a sudden freeze while in a fresh-growing state; and in both cases the consequence was excessive destruction the ensuing spring and summer.2. In consequence of this diagnosis, it has been found practicable to predict the blight six months before its development. The statement of this fact, on paper, may seem a small measure of proof; but it would weigh much with any candid man to be told, by an experienced nurseryman, this is such a fall as will make blight; to be taken, during the winter into the orchard, and told, this tree has been struck at the junction of these branches; that tree is not at all affected; this tree will die entirely the next season; this tree will go first on this side, etc., and to find, afterward, the prediction verified.3. This leads us to state separately, the fact, that, after such a fall, blighted-trees may be ascertained during the process of late winter or early spring pruning.In priming before the sap begins to rise freely, no sap should follow the knife in a healthy tree. But in trees which have been affected with blight, a sticky, viscid sap exudes from the wound.4. Trees which ripen their wood and leaves early, are seldom affected. This ought to elicit careful observation; for, if found true, it will be an important element in determining the value of varieties of the pear in the middle andwestern States, where the late and warm autumns render orchards more liable to winter blight than New England orchards. An Orange Bergamot, grafted upon an apple stock, had about run out; it made a small and feeble growth, and cast its leaves in the summer of 1843, long before frost. It escaped the blight entirely; while young trees, and of the same kind (we believe), standing about it, and growing vigorously till the freeze, perished the next season. I have before me a list of more than fifty varieties, growing in the orchard of Aaron Alldredge, of Indianapolis, and their history since 1836; and so far as it can be ascertained, late-growing varieties are the ones, in every case, subject to blight; and of those which have always escaped, the most part are known to ripen leaf and wood early.5. Wherever artificial causes have eitherproducedorpreventeda growth so late as to be overtaken by a freeze, blight has, respectively, beenfeltoravoided. Out of 200 pear-trees, only four escaped in 1832, in the orchard of Mr. Reagan. These four had, the previous spring, beentransplanted, and had made little or no growth during summer or fall. If, however, they had recovered themselves, during the summer, so as to grow in the autumn, transplanting would have had just the other effect; as was the case in a row of pear-trees, transplanted by Mr. Alldredge in 1843. They stood still through the summer and made growth in the fall—were frozen—and in 1844 manifested severe blight. Mr. Alldredge’s orchard affords another instructive fact. Having a row of the St. Michael pear (of which any cultivator might have been proud), standing close by his stable, he was accustomed, in the summer of 1843, to throw out, now and then, manure about them, to force their growth. Under this stimulus they were making excessive growth when winter-struck. Of all his orchard, they suffered, the ensuing summer, the most severely. Of twenty-two treestwelvewere affected by the blight, andeightentirely killed. Of seventeen trees of the Bell pear,eleven suffered, but none were killed. All in this region know the vigorous habit of this tree. Of eight Crassane Bergamot (a late grower), five were affected and two killed. In an orchard of 325 trees of 79 varieties, one in seven blighted, 25 were totally destroyed. Although a minute observation was not made on each tree, yet, as a general fact, those which suffered were trees of a full habit and of a late growth.6. Mr. White, a nurseryman near Mooresville, Morgan County, Indiana, in an orchard of from 150 to 200 trees, had not a single case of the blight in the year 1844, though all around him its ravages were felt. What were the facts in this case? His orchard is planted on a mound-like piece of ground; is high, of a sandy, gravelly soil: earlier by a week than nursery soils in this county; and in the summer of 1843 his trees grew through the summer; wound up and shed their leaves early in the fall, and during the warm spell made nosecond growth. The orchard, then, that escaped, was one on such a soil as insured anearlygrowth, so that the winter fell upon ripened wood.7. It may be objected, that if the blightbeganin the new and growing wood, it would appear there; whereas the seat of the evil,i. e.the place where the bark is diseased or dead, is lower down and on old wood. Certainly, it should be; for the returning sap falls some ways down before it effects a lodgment.8. It might be said thatspring-frostsmight produce this disease. But in the spring of 1834, in the last of May, after the forest-trees were in full leaf; there came frost so severe as to cut every leaf; and to this day the dead tops of the beech attest the power of the frost. But noblightoccurred that year in orchard, garden or nursery.9. It may be asked why forest-trees do not suffer. To some extent they do. But usually the dense shade preserves the moisture of the soil, and favors an equal growth during the spring and summer; so that the excitability ofthe tree is spent before autumn, and it is going to rest when frost strikes it.10. It may be inquired why fall-growing shrubs are not always blighted, since many kinds are invariably caught by the frost in a growing state.We reply, first, that we are not to say thateverytree or shrub suffers from cold in the same manner. We assert it of fruit-trees because it has been observed; it must be asserted of other trees only when ascertained.We reply more particularly, that amere frostis not supposed to do the injury. The conditions under which blight is supposed to originate are, a growing state of the tree, a suddenfreeze, and sudden thawing.We would here add, that many things are yet to be ascertained before this theory can be considered as settled; as the actual state of the sap after congelation, ascertained by experiment; the condition of sap-vessels, as ascertained by dissection; whether the congelation, or the thawing, or both, produce the mischief; whether the character of the seasonfollowingthe fall-injury may not materially modify the malignancy of the disease; seasons that are hot, moist and cloudy, propagating the evil; and others dry, and cool, restraining growth and the dsease. It is to be hoped that these points will be carefully investigated, not by conjecture, but by scientific processes.11. We have heard it objected, that trees grafted in the spring blight in the graft during the summer. If thestockhad been affected in the fall, blight would arise fromit; if the scion had, in common with the tree from which it was cut, been injured, blight must arise fromit.Blight is frequently caused in the nursery; and the cultivator, who has brought trees from a distance, and with much expense, has scarcely planted them before they show blight and die.12. It is objected, that while only a single branch is at first affected, the evil is imparted to the whole tree; notonly to the wood of the last year, but to the old branches. We reply, that if a single branch only should be affected by fall-frost, and be so severely affected as to become a repository of much malignant fluid, it might gradually enter the system of the whole tree, through the circulation. This fact shows, whycuttingis a partial remedy; every diseased branch removed, removes so much poison; it shows also why cutting frombelowthe seat of the disease (as if to fall below the haunt of a supposed insect), is beneficial. The farther the cut is made from that point where the sap has clogged the passages, the less of it will remain to enter the circulation.13. Trees of great vigor of constitution, in whose system but little poison exists, may succeed after a while in rejecting the evil, and recover. Where much enters the system, the tree must die; and with a suddenness proportioned to the amount of poison circulated.14. A rich anddrysoil would be likely to promote early growth, and the tree would finish its work in time; but a rich andmoistsoil, by forcing the growth, would prepare the tree for blight; so that rich soils may prevent or prepare for the blight, and the difference will be the difference of the respective soils in producing an early instead of a late growth.IV.Remedy.—So long as the blight was believed to be of insect origin, it appeared totally irremediable. If the foregoing reasoning be found correct, it will be plain that the scourge can only be occasional; that it may be in a degree prevented; and to some extent remedied where it exists.1. We should begin by selecting for pear orchards a warm, light, rich, dry and early soil. This will secure an early growth and ripe wood before winter sets in.2. So soon as observation has determined what kinds are naturally early growers and early ripeners of wood, such should be selected; as they will be least likely to come under those conditions in which blight occurs.3. Wherever orchards are already planted; or where a choice in soils cannot be had, the cultivator may know by the last of August or September, whether a fall-growth is to be expected. To prevent it, we suggest immediateroot-pruning. This will benefit the tree at any rate, and will probably, by immediately restraining growth, prevent blight.4. Whenever blight has occurred, we know of no remedy but free and earlycutting. In some cases it will remove all diseased matter; in some it will alleviate only; but in bad blight, there is neither in this, nor in anything else that we are aware of, any remedy.There are two additional subjects, with which we shall close this paper.1. This blight is not to be confounded withwinter-killing. In the winter of either 1837 or 1838, in March a deep snow fell (in the region of Indianapolis) and was immediately followed by brilliant sun. Thousands of nursery-trees perished in consequence, but without putting out leaves, or lingering. It is a familiar fact to orchardists, that severe cold, followed by warm suns, produce a bursting of the bark along the trunk; but usually at the surface of the ground.2. We call the attention of cultivators to the disease of the peach-tree, called “The Yellows.” We have not spoken of it as the same disease as theblightin the pear and the apple, only because we did not wish to embarrass this subject by too many issues. We will only say, that it is the opinion of the most intelligent cultivators among us, that the yellows are nothing but the development of the blight according to the peculiar habits of the peach-tree. We mention it, that observation may be directed to the facts.[18]Read before the Indiana Horticultural Society, and communicated by Mr. Beecher to Hovey’s Magazine of Horticulture, December, 1844.[19]Lindley’s Horticulture,p.81-82.[20]See Lindley,p.32.
Theyear 1844 will long be remembered for the extensive ravages of that disease hitherto denominatedfire-blight. Beginning at the Atlantic coast, we have heard of it in Pennsylvania, Maryland, Virginia, Ohio, Kentucky, Indiana, and as far as Tennessee; and it is probable that it has been felt in every fruit-growing State in the Union where the season of 1843 was the same as that west of the Alleghany range, namely, cold in spring, dry throughout the summer, and a wet and warm fall, with early and sudden winter.
In Indiana, and Ohio theblighthas prevailed to such an extent as to spread dismay among cultivators; destroying entire collections—taking half the trees in large orchards—affecting both young and old trees, whether grafted or seedings in soils of every kind. Many have seen the labor and fond hope of years cut off, in one season, by an invisible destroyer, against which none could guard; because, in the conflicting opinions, none were certain whether the disease was atmospheric, insect or chemical.
I shall now proceed to describe that blight known in the western States (without pretending to identify it with the blight known in New York and New England), to examine the theories proposed for its causation, and to present what now seems to me the true cause.
I.Description.—Although the signs of it, as will appear in the sequel, may be detected long before the leaves put out in the spring, yet its full effects do not begin to appear until May, or if the spring be backward, until June. On the wood of the last year will be found a point where thebark is either dead and dry, or else at the same point the bark will be puffed, softened, or sappy with thickened sap—these two appearances indicating only different degrees of the same blight. Wherever the bark is dead and dry, the limb will flourish above it, make new wood, ripen its fruit, but perish the ensuing winter. In the other case, as soon as the circulation of the sap becomes active, the point described shows signs of disease, the leaf turns to a darker brown than is natural to its ordinary decay, being nearly black, and the wood perishes.
The disease, at first, blights the terminal portions of the branch; but the affection spreads gradually downward, and sometimes affects the whole trunk. The time from the first appearance of the blight to that in which any affected part dies, is various; sometimes two or three weeks—sometimes a day only; and sometimes, but rarely, even a few hours consummate the disease.
On dissecting the branch, the wood is of a dirty, brownish, yellow color; the sap thick and unctuous, of a sour disagreeable odor, like that of a fermented watermelon, on the tops of potato vines after they have been frosted. In still, moist days, where the blight is extensive in an orchard, this odor fills the air, and is disagreeably perceptible at some distance from the trees.
Sometimes the bark bursts, the sap exudes, and runs down, turning black; and its acridity will destroy vegetation on which it may drop, and shoots, at a distance from the trunk, upon which the rain washes this ichor, will soon perish. When we come to treat of thecauseof this disease, it will be important to remember this malignancy of the fluids.
We are carefully to distinguish these appearances, peculiar to what I suppose ought to be calledwinter-blight, from another and asummer-blight. In this last, the leaf is affected at first in spots; gradually the whole leaf turns russet color and drops. Along the wood may be seen the hardenedtrail as of a slimy insect, of an ash color. Thewoodsuffers very little by this summer-blight, and sometimes none. The winter-blight is found on almost all kinds of trees. This summer it has affected the apple, the pear, the peach, the quince, the English hawthorn, privet, black birch, Spanish chestnut, elder, and calycanthus. I enumerate the most of these kinds on the authority of J. H. James, of Urbana, Ohio, and C. W. Elliott, of Cincinnati, having observed it myself only on fruit-trees.
II.Theories.—A variety of theories exist as to the causes of this disease. Some are mere imaginations; some are only ingenious; and some so near to what I suppose to be the truth, that it is hardly possible to imagine how the discovery was not made.
The injury is done in the fall, but is not seen till spring or summer, or even the next fall. Thus, six months or a year intervene between thecauseand theeffect—a sufficient reason for the difficulty of detecting the origin of the evil.
1. Some have alleged that the rays of the sun, passing through vapors which arise about the trees, concentrate upon the branches, and destroy them by the literal energy of fire. Were this true, the young and tender shoots would suffer first and most; all pear-trees would suffer alike; moist and hot summers would be affected with blight; herbaceous plants would suffer more than ligneous: all of which results are contrary to facts.
2. Some have supposed the soil to contain deleterious substances, or to be wanting in properties necessary to health. But in either case such a cause of the blight appears untrue, when we consider that trees suffer in all soils, rich or poor; that, in the same soil, one tree is blighted and the next tree escapes; that they will flourish for twenty years and then blight; that a tree partially diseased recovers, and thrives for ten or more years without recurrence of blight.
3. It has been attributed to violent and sudden changesof temperature in the air and of moisture in the earth; to sudden change from sward to high tillage; and the result is stated to be an “overplus” of sap, or a “surfeit.” All these causes occur every year; but the blight does not every year follow them. Changes of temperature, and violent changes in the condition of the soil, may bealliedwith the true cause. But whenonlythese things exist, no blight follows.
4. Others have attributed the disease to over-stimulation by high manuring, or constant tillage; and it has been said that covering the roots with stones and rubbish, or laying the orchard down to grass, would prevent the evil. Facts warrant no such conclusions. Pear-trees in Gibson County, Indiana, on a clay soil, with blue slaty subsoil, were affected this year more severely than any of which we have heard. Pears in southern parts of this State, on red clay, where the ground had long been neglected, suffered as much as along the rich bottom lands of the Wabash about Vincennes. If there was any difference it was in favor of the richest land. About Mooresville, Morgan County, Indiana, pears have been generally affected, and those in grass landsas muchas those in open soils. Aside from these facts, it is well known that pear-trees do not blight in those seasons when they make the rankest growth more than in others. They will thrive rampantly for years, no evil arising from their luxuriance, and then suddenly die of blight.
5. It has been supposed by a few to be the effect ofage, the disease beginning on old varieties, and propagated upon new varieties by contagion. Were this the true cause, we should expect it to be most frequently developed in those pear regions where old varieties most abound. But this disease seems to be so little known in England, that Loudon, in his elaborateEncyclopedia of Gardening, does not even mention it. Mr. Manning’s statement will be given further on, to the same purport.
6. Insect theory: The confidence with which eastern cultivators pronounce the cause to be aninsect, has in part served to cover up singular discrepancies in the separate statements in respect to the ravages, and even the species of this destroyer. TheGenesee Farmerof July, 1843, says, “the cause of the disease was for many years a matter of dispute, and is so still by some persons; but the majority are now fully convinced that it is the work of an insect (scolytus pyri).” T. W. Harris, in his work on insects, speaks of the minuteness and obscure habits of this insect, as “reasons why it has eluded the researches of those persons who disbelieve in its existence as the cause of the blasting of the limbs of thepear-tree.” Dr. Harris evidently supposed, until so late as 1843, that this insect infested only thepear-tree; for he says, “the discovery of the blight-beetle in the limbs of the apple-tree, is a new fact in natural history; but it is easily accounted for, because this tree belongs not only to the same natural group, but also to the same genus as the pear-tree. It is not, therefore, surprising, that both the pear and the apple-tree should occasionally be attacked by the same insect.” [See an article in theMassachusetts Ploughman, summer of 1843, quoted inGenesee Farmer, July, 1843.]
This insect is said to eat through thealburnum, the hard wood, and even a part of the pith, and to destroy the branch by separation of part from part, as a saw would. On these facts, which there is no room to question, we make two remarks.
1st. That the blight thus produced islimited, and probably sectional or local. No account has met my eye which leads me to suppose that any considerable injury has been done by it. Mr. Manning, of Salem,Mass., in the second edition of his “Book of Flowers,” states that he has never “had any trees affected by it”—the blight. Yet his garden and nursery has existed for twenty years, and contained immense numbers of trees.
2d. It is very plain that neither Mr. Lowell, originally, nor Dr. Harris, nor any who describe the blight as caused by the blight-beetle, had any notion of that disease which passes by the same name in the middle and western States. The blight of thescolytus pyriis a meregirdlingof the branches—a mechanical separation of parts; and no mention is made of the most striking facts incident to the great blight—the viscid unctuous sap; the bursting of the bark, through which it issues; and its poisonous effects on the young shoots upon which it drops.
We do not doubt the insect-blight; but we are sure that it is notourblight. We feel very confident, also, that this blight, which from its devastations may be called the great blight, has been felt in New England, in connection with the insect-blight, and confounded with it, and the effects of two different causes happening to appear in conjunction, have been attributed to one, and the least influential cause. The writer in Fessenden’sAmerican Gardener(Mr. Lowell?) says of the blight, “it is sometimes so rapid in its progress, that in a few hours from its first appearance the whole tree will appear to be mortally diseased.” This is not insect-blight; for did the blight-beetle eat sosuddenlyaround the wholetrunk? Now here is a striking appearance of the great blight, confounded with the minor blight, as we think will appear in the sequel.
This theory has stood in the way of a discovery of the true cause of the great blight; for every cultivator has gone in search of insects; they have been found in great plenty, and in great variety of species, and their harmless presence accused with all the mischief of the season. A writer in theFarmer’s Advocate, Jamestown,N. C., discerned the fire-blight, and traced it to “small,red, pellucid insects, briskly moving from place to place on the branches.” This is not thescolytus pyriofProf.Peck and Dr. Harris.
Dr. Mosher, of Cincinnati, in a letter published in theFarmer and Gardenerfor June, 1844, describes a thirdinsect—“very minute brown-colored aphides, snugly secreted in the axilla of every leaf on several small branches; … most of them were busily engaged with their proboscis inserted through the tender cuticle of this part of thepetioleof the leaf, feasting upon thevital juicesof the tree. The leaves being thus deprived of the necessary sap for nourishment and elaboration soon perished, … while all that part of the branch and trunk below, dependent upon the elaborated sap of the deadened leaves above, shrunk, turned black, and dried up,”p.261.
Lindley, in his work onHorticulture,p.42-46, has detailed experiments illustrating vegetableperspiration, from which we may form an idea of the amount of fluid which these “very-minute brown-colored aphides” would have to drink. A sunflower, three and a half feet high, perspired in a very warm day thirty ounces—nearly two pounds; on another day, twenty ounces. Taking the old rule, “a pint a pound,” nearly a quart of fluid was exhaled by a sunflower in twelve hours; and the vessels were still inflated with a fresh supply drawn from the roots. Admitting that the leaves of a fruit-tree have a less current of sap than a sunflower or a grape-vine, yet in the months of May and June, the amount of sap to be exhausted by these very minute brown aphides, would be so great, that if they drank it so suddenly as to cause a tree to die in a day, they would surely augment in bulk enough to be discovered without a lens. If some one had accounted for the low water in the Mississippi, in the summer of 1843, by saying that buffaloes had drank up all the upper Missouri, and cut off the supply, we should be at a loss which most to pity, the faith of the narrator, or the probable condition of the buffaloes after their feat of imbibition.
But the most curious resultsfollowthese feats of suction. The limbs and trunkbelowshrink and turn black, for want of that elaborated sap extracted by the aphides. And yet every year we perform artificially this very operation inringingordecorticationof branches, for the purpose of accelerating maturation or improving the fruit. Every year thesawtakes off a third, a half, and sometimes more, of a living tree; and the effect is to produce new shoots, not death. Is an operation which can be safely performed by man,deadlywhen performed by an insect? Dr. Masher did not detect the insects without extreme search, and then only in colonies, on healthy branches. Do whole trees wither in a day by the mere suction of such insects? Had they been supposed topoisonthe fluids, the theory would be less exceptionable, since poisons in minute quantities may be very malignant.
While we admit a limited mischief of insects, they can never be the cause of the prevalent blight of the middle and western States—such a blight as prevailed in and around Cincinnati in the summer of 1844—nor of that blight which prevailed in 1832. Theblight-beetle, after most careful search and dissection, has not been found, nor any trace or passage of it. Dr. Mosher’s insect may be set aside without further remark.
I think that further observation will confirm the following conclusions:
1. Insects are frequently found feeding in various ways upon blighted trees, or on trees which afterward become so.
2. Trees are fatally blighted on which no insects are discerned feeding—neither aphides norscolytus pyri.
3. Multitudes of trees have such insects on them as are in other cases supposed to cause the blight, without a sign of blight following. This has been the case in our own garden.
III.Cause of the Blight.—The Indiana Horticultural Society, early in the summer of 1844, appointed a committee to collect and investigate facts on the Fire-Blight. While serving on this committee, and inquiring in all the pear-growing regions, we learned that Reuben Reagan, of Putnam County, Ind., was in possession of much information, andsupposed himself to have discovered the cause of this evil; and to him we are indebted for a first suggestion of the cause. Mr. Reagan has for more than twelve years past suspected that this disease originated in the fall previous to the summer on which it declares itself. During the last winter Mr. Reagan predicted the blight, and in his pear-orchards he marked the trees that would suffer, and pointed to the spot which would be the seat of the disease; and his prognostications were strictly verified. After gathering from him all the information which a limited time would allow, we obtained from Aaron Alldredge, of Indianapolis, a nurseryman of great skill, and possessed of careful, cautious habits of observation, much corroborative information; and particularly a tabular account of the blight for nine years past in his nursery and orchard.
The spring of 1843 opened early, but cold and wet, until the last of May. The summer was both dry and cool, and trees made very little growth of new wood. Toward autumn, however, the drought ceased, copious rains saturated the ground, and warm weather started all trees into vigorous, though late, growth. At this time, while we hoped for a long fall and a late winter, on the contrary we were surprised by an early and sudden winter, and with unusual severity at the very beginning. In the West, much corn was ruined and more damaged; and hundreds of bushels of apples were caught on the trees and spoiled—one cultivator alone losing five hundred bushels. Caught in this early winter, what was the condition of fruit-trees? They were making rapid growth, every part in a state of excitement, the wood unripe, the passages of ascent and descent impleted with sap. In this condition, the fluids were suddenly frozen—the growth instantly checked; and the whole tree, from a state of great excitability, was, by one shock, rudely forced into a state of rest. Warm suns, for a time, followed severe nights. What would be the effect of this freezing and sudden thawing upon the fluids andtheir vessels? We have been able to find so little written upon vegetable morbid anatomy (probably from the want of access to books), that we can give but an imperfect account of the derangement produced upon the circulating fluids by congelation. We cannot state the specific changes produced by cold upon the ascending sap, or on the cambium, nor upon the elaborated descending current. There is reason to suppose that the two latter only suffer, and probably only the last. That freezing and thawing decompose the coloring matter of plants is known; but what other decomposition, if any, is effected, we know not. The effect of congelation upon the descending sap of pear and apple-trees, is to turn it to a viscid, unctuous state. It assumes a reddish brown color; becomes black by exposure to the air; is poisonous to vegetables even when applied upon the leaf. Whether in some measure this follows all degrees of congelation, or only under certain conditions, we have no means of knowing.
The effect of freezing and thawing upon the tissues and sap-vessels is better known. Congelation is accompanied with expansion; the tender vessels are either burst or lacerated; the excitability of the parts is impaired or destroyed; the air is expelled from the aëriferous cavities, and forced into the passages for fluids; and lastly, the tubes for the conveyance of fluids are obstructing by a thickening of their sides.[19]The fruit-trees, in the fall of 1843, were then brought into a morbid state—the sap thickened and diseased; the passages lacerated, obstructed, and probably, in many instances burst. The sap elaborated, and now passing down in an injured state, would descend slowly, by reason of its inspissation, the torpidity of the parts, and the injured condition of the vessels. The grosser parts, naturally the most sluggish, would tend to lodge and gradually collect at the junction of fruit-spurs, the forks of branches,or wherever the condition of the sap-vessels favored a lodgment. In some cases the passages are wholly obstructed; in others, only in part.
At length the spring approaches. In early pruning, the cultivator will find, in those trees which will ere long develop blight, that the knife is followed by an unctuous sap, and that the liber is of a greenish yellow color. These will be the first signs, and the practised eye may detect them long before a leaf is put forth.
When the season is advanced sufficiently to excite the tree to action, the sap will, as usual, ascend by the alburnum, which has probably been but little injured; the leaf puts out, and no outward sign of disease appears; nor will it appear until the leaf prepares the downward current. May, June and July, are the months when the growth is most rapid, and when the tree requires the most elaborate sap; and in these months the blight is fully developed. When the descending fluid reaches the point where, in the previous fall, a total obstruction had taken place, it is as effectually stopped as if the branch were girdled. For the sap which had lodged there would, by the winds and sun, be entirely dried. This would not be the case if the sap was good and the vitality of the wood unimpaired; but where the sap and vessels are both diseased, the sun affects the branch on the tree just as it would if severed and lying on the ground. There will, therefore, be found on the tree, branches with spots where the bark is dead and shrunk away below the level of the surrounding bark; and at these points the current downward is wholly stopped. Only theoutwardpart, however, is dead, while thealburnum, or sap-wood, is but partially injured. Through the alburnum, then, the sap from the roots passes up, enters the leaf, and men are astonished to see a branch, seemingly dead in the middle, growing thriftily at its extremity. No insect-theory can account for this case; yet it is perfectly plain and simple when we consider that there are two currentsof sap, one of which may be destroyed, and the other for alimited timego on. The blight, under this aspect, is nothing butringingordecortication, effected by diseased sap, destroying the parts in which it lodges, and then itself drying up. The branch will grow, fruit will set, and frequently become larger and finer flavored than usual.
But in a second class of cases, the downward current comes to a point where the diseased sap had effected only a partial lodgment. The vitality of the neighboring parts was preserved, and the diseased fluids have been undried by wind or sun, and remain more or less inspissated. The descending current meets and takes up more or less of this diseased matter, according to the particular condition of the sap. Wherever the elaborated sap passes, after touching this diseased region, it will carry its poison along with it down the trunk, and, by the lateral vessels, in toward the pith. We may suppose that a violence which would destroy the health of the outer parts, would, to some degree, rupture the inner sap-vessels. By this, or by some unknown way, the diseased sap is taken into the inner,[20]upward current, and goes into the general circulation. If it be in a diluted state, or in small quantities, languor and decline will be the result; if in large quantities, and concentrated, the branch will die suddenly, and the odor of it will be that of frost-bitten vegetation. All the different degrees of mortality result from the quantity and quality of the diseased sap which is taken into circulation. In conclusion, then, where, in one class of cases, the feculent matter was, in the fall, so virulent as to destroy the parts where it lodged, and was then dried by exposure to wind and sun, the branch above will live, even through the summer, but perish the next winter; and the spring afterward, standing bare amid green branches, the cultivator may suppose the branch tohave blighted that spring, although the cause of death was seated eighteen months before. When, in the other class of cases, the diseased sap is less virulent in the fall, but probably growing worse through the spring, a worse blight ensues, and a more sudden mortality.
We will mention some proofs of the truth of this explanation.
1. The two great blight years throughout the region of Indianapolis, 1832 and 1844, were preceded by a summer and fall such as we have described. In the autumns of both 1831 and 1843, the orchards were overtaken by a sudden freeze while in a fresh-growing state; and in both cases the consequence was excessive destruction the ensuing spring and summer.
2. In consequence of this diagnosis, it has been found practicable to predict the blight six months before its development. The statement of this fact, on paper, may seem a small measure of proof; but it would weigh much with any candid man to be told, by an experienced nurseryman, this is such a fall as will make blight; to be taken, during the winter into the orchard, and told, this tree has been struck at the junction of these branches; that tree is not at all affected; this tree will die entirely the next season; this tree will go first on this side, etc., and to find, afterward, the prediction verified.
3. This leads us to state separately, the fact, that, after such a fall, blighted-trees may be ascertained during the process of late winter or early spring pruning.
In priming before the sap begins to rise freely, no sap should follow the knife in a healthy tree. But in trees which have been affected with blight, a sticky, viscid sap exudes from the wound.
4. Trees which ripen their wood and leaves early, are seldom affected. This ought to elicit careful observation; for, if found true, it will be an important element in determining the value of varieties of the pear in the middle andwestern States, where the late and warm autumns render orchards more liable to winter blight than New England orchards. An Orange Bergamot, grafted upon an apple stock, had about run out; it made a small and feeble growth, and cast its leaves in the summer of 1843, long before frost. It escaped the blight entirely; while young trees, and of the same kind (we believe), standing about it, and growing vigorously till the freeze, perished the next season. I have before me a list of more than fifty varieties, growing in the orchard of Aaron Alldredge, of Indianapolis, and their history since 1836; and so far as it can be ascertained, late-growing varieties are the ones, in every case, subject to blight; and of those which have always escaped, the most part are known to ripen leaf and wood early.
5. Wherever artificial causes have eitherproducedorpreventeda growth so late as to be overtaken by a freeze, blight has, respectively, beenfeltoravoided. Out of 200 pear-trees, only four escaped in 1832, in the orchard of Mr. Reagan. These four had, the previous spring, beentransplanted, and had made little or no growth during summer or fall. If, however, they had recovered themselves, during the summer, so as to grow in the autumn, transplanting would have had just the other effect; as was the case in a row of pear-trees, transplanted by Mr. Alldredge in 1843. They stood still through the summer and made growth in the fall—were frozen—and in 1844 manifested severe blight. Mr. Alldredge’s orchard affords another instructive fact. Having a row of the St. Michael pear (of which any cultivator might have been proud), standing close by his stable, he was accustomed, in the summer of 1843, to throw out, now and then, manure about them, to force their growth. Under this stimulus they were making excessive growth when winter-struck. Of all his orchard, they suffered, the ensuing summer, the most severely. Of twenty-two treestwelvewere affected by the blight, andeightentirely killed. Of seventeen trees of the Bell pear,eleven suffered, but none were killed. All in this region know the vigorous habit of this tree. Of eight Crassane Bergamot (a late grower), five were affected and two killed. In an orchard of 325 trees of 79 varieties, one in seven blighted, 25 were totally destroyed. Although a minute observation was not made on each tree, yet, as a general fact, those which suffered were trees of a full habit and of a late growth.
6. Mr. White, a nurseryman near Mooresville, Morgan County, Indiana, in an orchard of from 150 to 200 trees, had not a single case of the blight in the year 1844, though all around him its ravages were felt. What were the facts in this case? His orchard is planted on a mound-like piece of ground; is high, of a sandy, gravelly soil: earlier by a week than nursery soils in this county; and in the summer of 1843 his trees grew through the summer; wound up and shed their leaves early in the fall, and during the warm spell made nosecond growth. The orchard, then, that escaped, was one on such a soil as insured anearlygrowth, so that the winter fell upon ripened wood.
7. It may be objected, that if the blightbeganin the new and growing wood, it would appear there; whereas the seat of the evil,i. e.the place where the bark is diseased or dead, is lower down and on old wood. Certainly, it should be; for the returning sap falls some ways down before it effects a lodgment.
8. It might be said thatspring-frostsmight produce this disease. But in the spring of 1834, in the last of May, after the forest-trees were in full leaf; there came frost so severe as to cut every leaf; and to this day the dead tops of the beech attest the power of the frost. But noblightoccurred that year in orchard, garden or nursery.
9. It may be asked why forest-trees do not suffer. To some extent they do. But usually the dense shade preserves the moisture of the soil, and favors an equal growth during the spring and summer; so that the excitability ofthe tree is spent before autumn, and it is going to rest when frost strikes it.
10. It may be inquired why fall-growing shrubs are not always blighted, since many kinds are invariably caught by the frost in a growing state.
We reply, first, that we are not to say thateverytree or shrub suffers from cold in the same manner. We assert it of fruit-trees because it has been observed; it must be asserted of other trees only when ascertained.
We reply more particularly, that amere frostis not supposed to do the injury. The conditions under which blight is supposed to originate are, a growing state of the tree, a suddenfreeze, and sudden thawing.
We would here add, that many things are yet to be ascertained before this theory can be considered as settled; as the actual state of the sap after congelation, ascertained by experiment; the condition of sap-vessels, as ascertained by dissection; whether the congelation, or the thawing, or both, produce the mischief; whether the character of the seasonfollowingthe fall-injury may not materially modify the malignancy of the disease; seasons that are hot, moist and cloudy, propagating the evil; and others dry, and cool, restraining growth and the dsease. It is to be hoped that these points will be carefully investigated, not by conjecture, but by scientific processes.
11. We have heard it objected, that trees grafted in the spring blight in the graft during the summer. If thestockhad been affected in the fall, blight would arise fromit; if the scion had, in common with the tree from which it was cut, been injured, blight must arise fromit.
Blight is frequently caused in the nursery; and the cultivator, who has brought trees from a distance, and with much expense, has scarcely planted them before they show blight and die.
12. It is objected, that while only a single branch is at first affected, the evil is imparted to the whole tree; notonly to the wood of the last year, but to the old branches. We reply, that if a single branch only should be affected by fall-frost, and be so severely affected as to become a repository of much malignant fluid, it might gradually enter the system of the whole tree, through the circulation. This fact shows, whycuttingis a partial remedy; every diseased branch removed, removes so much poison; it shows also why cutting frombelowthe seat of the disease (as if to fall below the haunt of a supposed insect), is beneficial. The farther the cut is made from that point where the sap has clogged the passages, the less of it will remain to enter the circulation.
13. Trees of great vigor of constitution, in whose system but little poison exists, may succeed after a while in rejecting the evil, and recover. Where much enters the system, the tree must die; and with a suddenness proportioned to the amount of poison circulated.
14. A rich anddrysoil would be likely to promote early growth, and the tree would finish its work in time; but a rich andmoistsoil, by forcing the growth, would prepare the tree for blight; so that rich soils may prevent or prepare for the blight, and the difference will be the difference of the respective soils in producing an early instead of a late growth.
IV.Remedy.—So long as the blight was believed to be of insect origin, it appeared totally irremediable. If the foregoing reasoning be found correct, it will be plain that the scourge can only be occasional; that it may be in a degree prevented; and to some extent remedied where it exists.
1. We should begin by selecting for pear orchards a warm, light, rich, dry and early soil. This will secure an early growth and ripe wood before winter sets in.
2. So soon as observation has determined what kinds are naturally early growers and early ripeners of wood, such should be selected; as they will be least likely to come under those conditions in which blight occurs.
3. Wherever orchards are already planted; or where a choice in soils cannot be had, the cultivator may know by the last of August or September, whether a fall-growth is to be expected. To prevent it, we suggest immediateroot-pruning. This will benefit the tree at any rate, and will probably, by immediately restraining growth, prevent blight.
4. Whenever blight has occurred, we know of no remedy but free and earlycutting. In some cases it will remove all diseased matter; in some it will alleviate only; but in bad blight, there is neither in this, nor in anything else that we are aware of, any remedy.
There are two additional subjects, with which we shall close this paper.
1. This blight is not to be confounded withwinter-killing. In the winter of either 1837 or 1838, in March a deep snow fell (in the region of Indianapolis) and was immediately followed by brilliant sun. Thousands of nursery-trees perished in consequence, but without putting out leaves, or lingering. It is a familiar fact to orchardists, that severe cold, followed by warm suns, produce a bursting of the bark along the trunk; but usually at the surface of the ground.
2. We call the attention of cultivators to the disease of the peach-tree, called “The Yellows.” We have not spoken of it as the same disease as theblightin the pear and the apple, only because we did not wish to embarrass this subject by too many issues. We will only say, that it is the opinion of the most intelligent cultivators among us, that the yellows are nothing but the development of the blight according to the peculiar habits of the peach-tree. We mention it, that observation may be directed to the facts.
[18]Read before the Indiana Horticultural Society, and communicated by Mr. Beecher to Hovey’s Magazine of Horticulture, December, 1844.
[19]Lindley’s Horticulture,p.81-82.
[20]See Lindley,p.32.