The year 1844 will long be remembered for the extensive ravages of
that disease hitherto denominated _fire-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 the _blight_ has 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 the bark 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 the _cause_ of
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 called _winter-blight_, from another and a
_summer-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 hardened trail as of a slimy insect, of an ash color.
The _wood_ suffers 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
the _cause_ and the _effect_—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 changes of 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 be _allied_ with the true
cause. But when _only_ these 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 lands
_as much_ as 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 of _age_, 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 elaborate _Encyclopedia 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 an _insect_, 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. The _Genesee Farmer_
of 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 the _pear-tree_.” Dr. Harris
evidently supposed, until so late as 1843, that this insect infested
only the _pear-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 the _Massachusetts Ploughman_, summer of 1843, quoted in _Genesee
Farmer_, July, 1843.]
This insect is said to eat through the _alburnum_, 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 is _limited_, 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 the _scolytus
pyri_ is a mere _girdling_ of 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 not
_our_ blight. 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’s _American 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 so _suddenly_ around the whole _trunk_? 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 the _Farmer’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 the _scolytus pyri_ of Prof. Peck and Dr. Harris.
Dr. Mosher, of Cincinnati, in a letter published in the _Farmer and
Gardener_ for June, 1844, describes a third insect—“_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 the
_petiole_ of the leaf, feasting upon the _vital juices_ of 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 on _Horticulture_, p. 42-46, has detailed
experiments illustrating vegetable _perspiration_, 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 results _follow_ these feats of suction. The
limbs and trunk _below_ shrink and turn black, for want of that
elaborated sap extracted by the aphides. And yet every year we perform
artificially this very operation in _ringing_ or _decortication_ of
branches, for the purpose of accelerating maturation or improving the
fruit. Every year the _saw_ takes 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, _deadly_
when 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 to _poison_ the 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. The _blight-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 nor _scolytus 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,
and supposed 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 and their 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 the
_outward_ part, however, is dead, while the _alburnum_, 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
currents of sap, one of which may be destroyed, and the other for a
_limited time_ go on. The blight, under this aspect, is nothing but
_ringing_ or _decortication_, 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 to have 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 and western 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 either _produced_ or _prevented_ a
growth so late as to be overtaken by a freeze, blight has,
respectively, been _felt_ or _avoided_. Out of 200 pear-trees, only
four escaped in 1832, in the orchard of Mr. Reagan. These four had,
the previous spring, been _transplanted_, 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 trees _twelve_ were affected by the blight, and _eight_
entirely 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 no _second
growth_. The orchard, then, that escaped, was one on such a soil as
insured an _early_ growth, so that the winter fell upon ripened wood.
7. It may be objected, that if the blight _began_ in 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 that _spring-frosts_ might 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 no _blight_ occurred 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 of the 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 that _every_ tree 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 a _mere frost_ is not supposed to do
the injury. The conditions under which blight is supposed to originate
are, a growing state of the tree, a sudden _freeze_, 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 season _following_ the 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 the _stock_ had been affected in
the fall, blight would arise from _it_; if the scion had, in common
with the tree from which it was cut, been injured, blight must arise
from _it_.
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; not only 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, why _cutting_ is a partial remedy; every diseased
branch removed, removes so much poison; it shows also why cutting from
_below_ the 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 and _dry_ soil would be likely to promote early growth, and
the tree would finish its work in time; but a rich and _moist_ soil,
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 immediate _root-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
early _cutting_. 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 with _winter-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 the _blight_ in 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.