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.