_Of_ BLIGHT.
Wheat is blighted at Two Seasons; First, when in the Blossom; and then
its Generation is prevented and many of the Husks are empty in the Ear,
the Grains not being impregnated.
Secondly, Wheat is blighted, when the Grains are brought to the time of
their Maturity, but are light, and of little Value for making of Bread;
because they are not well filled with Flour.
The First cannot happen in _England_ by the Frost because the Winters
do not suffer it to grow so much, as to come into Blossom before the
Month of _June_; but they are long continual Rains that rot or chill
the Blossoms, and prevent their Fertility. Yet this is what seldom
happens to any great Degree. Wheat that grows in open Fields has some
Advantage from the Wind, that dislodges the Water sooner from the
Ears, than it can do in sheltry Places; and Lammas Wheat does not
hold the Drops of Rain so long as the Bearded (or Cone) Wheat, which
received very great Damage by this sort of Blight in the Year 1725, the
like never having been heard of before.
The Second sort of Blight, _viz._ from light Ears, is that which is
most frequent, and more general: This brings the greatest Scarcity of
Wheat. The Cause is plainly Want of Nourishment to perfect the Grain,
by whatever means that Want is occasioned.
Several Accidents kill the Plants, or injure their Health, and then
the Grains are not filled; as Lightning, the Effects whereof may
be observed by the blackish Spots and Patches in Fields of Wheat,
especially in such Years as have more of it than usual. Against this
there is no Defence.
The other Causes of the Blight, which are most general, and do the most
Damage, may, in some measure, be prevented.
One Cause is the lodging or falling of Corn; for then the Stalks are
broken near the Ground, whereby many of the Vessels are so pressed,
that the Juices cannot pass them; and then the free Circulation is
hindered; the Chyle cannot mount in sufficient Quantity to be purified,
and turned into Sap; the Defect whereof makes the Plants become
languid, and only just able to live; they have Strength enough to
linger on to the time of their Period, as in very old Age, but not to
bring their Fruit, which is the Grain, to its natural Bulk, nor to fill
it with Flour: and the sooner the Stalks fall, the less and thinner the
Grain will be.
Hence it often happens, that when Tillage, Dung, and good Land have
brought a Crop of Wheat, that in the Months of _April_ and _May_
promise to yield the Owner Five or Six Quarters on an Acre, then in
_June_ it falls down, and scarce affords Five or Six Bushels; and that
perhaps is so thin and lank, that the Expence of reaping and threshing
it may overbalance its Value.
That the falling down of Wheat does cause the Ruin of the Crop, is well
known; but what causes it to fall, is not so plain.
And, without knowing the true Causes, ’tis not likely that a Remedy
should be found against the Disease.
I take this Weakness of the Stalks, which occasions their falling, to
proceed from want of Nourishment, want of Air, want of the Sun’s Rays,
or of all Three.
One Argument, that it lodges for want of Nourishment, is, that a rich
Acre has maintain’d a Crop of Five Quarters standing, when another
poorer Acre was not able to support a Crop from falling, which was but
large enough to have brought Three Quarters, if it had stood: and this
in the same Year, and on the same Situation. And ’tis very plain, that
if one Acre was twice as rich as the other, it must be able to nourish
Five Quarters better than the other could nourish Three Quarters.
Air is necessary to the Life and Health of all Plants, tho’ in very
different Degrees: Aquatics, which live under Water, are content with
as little Air, as their Companions the Fishes.
But Wheat, being a terrestrial Plant, (tho’ in Winter it will live many
Days under Water, whilst the slow Motion of its Sap gives it little
or no Increase), requires a free open Air, and does not succeed so
well in low sheltery Places, as upon higher and opener Situations;
where the Air has a greater Motion, and can more easily carry off the
Recrements from the Leaves, after it has shaken off the Dews and Rains,
which would otherwise suffocate the Plants; and therefore the Leaves
are made so susceptible of Motion from the Air, which frees them from
the Dews, that would stop in the Recrements at the _Vesiculæ_ of the
Leaves, but shaken down will nourish the Plants at the Roots: The want
of this Motion weakening the Wheat, ’tis (as Animals in the like sickly
Case are) the more unable to stand, and the more liable to be press’d
down by the Weight of Rain-water, and more unable to rise up again when
down: All which Evils are remov’d by the free Motion of the Air, which
shakes off both Dews and Rains, and thus contributes to prevent the
falling (or lodging) of Wheat.
A great Quantity also of the Sun’s Rays is necessary to keep Wheat
strong, and in Health; and in _Egypt_, and other hot Countries, it is
not so apt to fall, as it is when sown in Northern Climates, tho’ the
Produce of the South be the greatest[152].
[152] This proves that the Crop doth not lodge on account of its
Bigness.
It may be observ’d, that every Leaf is inserted into a Sort of Knot,
which probably delivers the Sap to be depurated at the _Vesiculæ_ of
the Leaves, and then receives it back again for the Nourishment of
the Plant, doing for that Purpose the Office of an Heart: But the Sun
with his Rays supplies the Part of Pulse, to keep the Sap in Motion,
and carry on its Circulation, instead of the Heart’s _Systole_ and
_Diastole_. Wheat, being doubtless originally a Native of a hot
Country, requires by its Constitution a considerable Degree of Heat
to bring it to Perfection; and if much of that Degree be wanting, the
Wheat will be the weaker; and when the Solar Rays cannot reach the
lower Parts of the Stalks, the lowest Leaves and Knots cannot do their
Office; for which Reason the Chyle must mount higher before it be made
into Sap, and there must be then a greater Mixture of crude Chyle next
to the Ground, as by the white Colour it appears[153]. By this Means
that Part, which, if it had a due Share of the Sun’s Influence, would
be harden’d like a Bone or Spring, for the Support of the Stalks, for
lack of that, becomes more like to a Cartilage, soft and weak, unable
to sustain the Weight of the bending Ear, which, having its greatest
_Impetus_ against this Part, which is most feeble to resist it, it
yields, and lets it fall to the Ground; and then the Grain will be
blighted.
[153] But now I suspect this to be a Mistake, it being more likely,
that the white Colour of the Rind is owing to the Absence of the Sun
and free Air, than to the Chyle, as the Skin of those Parts of our
own Bodies that are concealed from them, is whiter than of those
which are exposed to them, though no Chyle-vessel comes near our Skin.
There is also another Cause of the Blight; and that is, the Wheat’s
coming too late into Blossom. The usual Time is the Beginning of
_June_; and if it be later, the Days shorten so fast after the
Solstice, that the Autumn of the Year hastening the Autumn of the
Wheat’s Life, the full Time of its Pregnancy[154] is not accomplish’d;
and then its Fruit, which is the Grain, becomes as it were abortive,
and not full-grown. This Time betwixt the Generation, Blossoming, and
the Maturity of the Grain, is, or ought to be, about Two Months.
[154] _Ut enim Mulieres habent ad Partum Dies certos, sic Arbores ac
Fruges._ Varro, _Lib._ 1. _Cap._ 44.
_Mense Maio florent; sic Frumenta, & Ordeum, & quæ sunt Seminis
singularis, Octo diebus florebunt, & deinde per Dies_ 40.
_grandescunt Flore deposito usque ad Maturitatis Eventum._ Palladius,
_Pag._ 114, 115.
_Quindecim Diebus esse in Vaginis, Quindecim florere, Quindecim
exarescere, cum sit maturum Frumentum._ Varro, _Lib._ 1. _Cap._ 32.
But the different Heat that there is in different Climates, may alter
both the Time that Plants continue in Blossom, and the Time betwixt
the Blossoming and the Ripening.
Therefore ’tis advantageous to hasten, what we can, the Time of
Blossoming, and to protract the Time of Ripening: And ’tis observ’d,
that the earliest sown Wheat generally escapes the Blight the best,
because it comes first into Blossom.
Feeding down the Wheat with Sheep prevents the Blight, by doing what
the Blight wou’d do, if the Wheat fell down, _i. e._ causes the Ears to
be light[155].
[155] Heavy Ears never fall. If they did, that would not make them
light. Wheat falls sometimes whilst ’tis in Grass, and before it
comes into Ear; so far are the Ears from causing it to fall. This was
proved by my whole Crop the last Harvest, and particularly by the
_Measured Acre_, the Ears of which, tho’ prodigious large and heavy,
were none of them lodg’d, when those of sown Wheat on the other Side
of the Hedge were fallen down flat, and lodg’d on the Ground.
And we find, that those who practise this Method of feeding their Wheat
with Sheep in the Spring, to prevent the lodging of it, have most
commonly their Straw weak, and Ears light.
These, instead of making the Stalks strong enough to support heavy
Ears, make the Ears light enough to be supported by weak Stalks. They
know that heavy Ears make the greatest Crop; and yet they still hope to
have it from light ones.
They _cause_ the _Blight_ by the very means they make use of to _cure_
it.
This feeding of Wheat much retards the Time of its blossoming; and that
it may blossom early, is one chief End of sowing it early, to prevent
the Blight. But when it is fed, what the Plants send up next is but
a Sort of second or latter Crop, which has longer to stand than the
first would have required, and is always weaker than the first Crop
would have been; and the longer time it has to continue on the Ground,
the more Nourishment is required to maintain it; and yet, as has been
shewn, the longer it has been sown, the more the Earth has lost of its
Nourishment; and consequently, the Crop will be yet weaker, and in
more Danger of the starving Blight[156].
[156] I am sure, that whenever Sheep break into my drill’d Wheat
in the Spring, it lessens my Crop half, just as far as they eat
the Rows. There are several Reasons why Sheep are more injurious
to drilled Wheat than sown; I would not therefore be understood to
decry the Practice of seeding sown Wheat, when the Thickness and
Irregularity of its Plants make it necessary: I have only endeavoured
to shew, that that Practice is founded upon a false Theory. For, if
Wheat fell down by reason of the Luxuriance of it; a Plant of it
would be more likely to fall when single, and at a great Distance
from every other Plant, than when near to other Plants, because such
a single Plant is (_cæteris paribus_) always the most luxuriant; and
I have not seen such a one fall (except Birds pull down the Ears),
but have observed the contrary, though its Ears are the largest.
The Subject I write on is Drilling and Hoeing, and of whatsoever else
I think relates to the Practice or Theory thereof; which obliges me
to advise against Drilling too thick upon any Sort of Land; but more
especially upon very rich Land: For though I have no such Land, yet
I apprehend, that a too great Number of Plants may overstock the
Rows, and cause them to be liable to some of the Inconveniences of
sown Wheat; and in such a Case, perhaps, Sheep may be rather useful
than prejudicial to the drilled Wheat; but of this I have had no
Experience: And if it should be too thick, it will be owing to the
Fault of the Manager or Driller; but, I suppose, it might be a better
Remedy to cut out the superfluous Plants by the Hand-hoe, in the
manner that superfluous Turneps are hoed out.
The most effectual Remedy against the Blight is that which removes all
its Causes (except such extraordinary ones as Lightning); as,
First, _Want of Nourishment_.
The Horse-hoe will, in wide Intervals, give Wheat, throughout all the
Stages of its Life, as much Nourishment as the discreet Hoer pleases.
Secondly, _Want of Air_.
Air, being a Fluid, moves most freely in a right or strait Line; for
there the fewest of its Parts meet with any Resistance; as a strait
River runs swifter than a crooked one, from an equal Declivity; because
more of the Water strikes against the Banks at the Turnings, and is
there somewhat retarded: and the rest moving no faster than in the
strait River, the whole Stream of the crooked must be slower in its
Course, than that of the strait River.
The Air cannot pass thro’ sown Corn in a direct Line, because it must
strike against, and go round every Plant, they standing all in the Way
of its Course, which must stop its Current near the Earth.
And the Air amongst sown Corn is like Water amongst Reeds or Osiers in
the Side of a River; it is so stopp’d in its Course, that it almost
becomes an Eddy; and since Air is about Eight hundred Times lighter
than Water, we may suppose its Current thro’ the Corn is more easily
retarded, especially near the Earth, where the Corn has occasion for
the greatest Quantity of Air to pass: For, tho’ the upper Part of the
Wheat be not able to stop a slow Current of Air, yet it does so much
raise even a swift one, as to throw it off from the Ground, and hinder
it from reaching the lower Parts of the Stalks, where the Air must
therefore remain, in a manner, stagnant; and the thicker the Wheat is,
where it stands promiscuously, the less Change of Air can it have, tho’
the greater the Number of the Stalks is, the more fresh Air they must
require.
But the confused Manner in which the Plants of sown Wheat stand, is
such, that they must all oppose the free Entrance of Air amongst them,
from whatever Point of the Compass it comes.
Now it is quite otherwise with Wheat drill’d regularly with wide
Intervals; for therein the Current of Air may pass freely (like Water
in a strait River, where there is no Resistance), and communicate
its Nitre to the lower as well as upper Leaves, and carry off the
Recrements they emit, not suffering the Plants to be weakened, as
an Animal is, when his Lungs are forc’d to take back their own
Expirations, if debarr’d from a sufficient Supply of fresh untainted
Air. And this Benefit of fresh Air is plentifully, and pretty equally,
distributed to every Row in a Field of ho’d Wheat.
Thirdly, _Want of the Sun’s Rays_.
Sown Wheat-plants, by their irregular Position, may be said to stand in
one another’s Light, for want of which they are apt to fall.
’Tis true the whole Field of Plants receive the same Quantity of
Sun-beams amongst them, whether they stand confusedly, or in Order: But
there is a vast Difference in the Distribution of them; for none or the
very least Share of Beams is obtain’d by those Parts which need the
greatest Share, in the confused Plants. And when the crural Parts, that
should support the whole Body of every Plant, are depriv’d of their
due Share of what is so necessary to strengthen them, the Plants (like
Animals in the same Case) are unable to stand.
But in drill’d Wheat, where the Plants stand in a regular Order, the
Sun-beams are more duly distributed to all Parts of the Plants in the
Ranks; for which Way soever the Rows are directed, if they be strait,
the Rays must, some time of the Day, fall on the Intervals, and be
reflected by the Ground, whence the lower Parts of the Wheat-stalks
must receive the greater Share of Heat, being nearest to the Point of
Incidence, having no Weeds to shadow them.
As to that Cause of the Blight, _viz._ the Wheat’s dying before the
full Time of its Pregnancy be accomplish’d; the Hoe removes all the
Objections against planting early, and then it will blossom the
earlier: And it has visibly kept Wheat green a whole Week longer, than
unho’d Wheat adjoining to it, planted the same Day.
The Antients were perfect Masters of the Vine-Husbandry, which seems
to have so engross’d their rural Studies, that it did not allow them
so much Reflection, as to apply the Use of those Methods to the
Increase of Bread, which they had discover’d to be most beneficial for
the Increase of Wine. One Method was, to hoe the Vines after they had
blossom’d, in order to fill the Fruit, as in _Columella_, Lib. iv.
Cap. 28. _Convenit tum crebris Fossionibus implere: nam fit ulterior
Pulverationibus._ And if what _Palladius_ says, _Tit._ ix. be true of
the Sarritions and Sarculations in the Month of _January_, and that if
Beans do twice undergo that scratching Operation, they will produce
much Fruit, and so large as to fill the Bushel almost as full when
shal’d as unshal’d.
_Faba, si bis sarculetur, proficiet, & multum Fructum & maximum
afferet, ut ad Mensuram Modii complendi fresa propemodum sicut Integra
respondeat._
This is to be done when Beans are Four Fingers high, and Corn when it
has Four or Five Leaves to a Plant; even then the Harrowing-work, tho’
it tore up some of the Plants, yet it was observ’d to do Good against
the Blight.
_Si siccas Segetes sarculaveris, aliquid contra Rubiginem præstitisti,
maxime si Ordeum siccum sarrietur._
When the Antients observ’d this, ’tis a Wonder they did not plant their
Corn so as to be capable of receiving this Benefit in Perfection. They
might have imagin’d, that what was effectual against the Blight, when
the Corn was in Grass, must, in all Probability, be much more effectual
when in Ear.
But the most general Blight that happens to Wheat in cold Climates,
is caused by Insects, which (some think) are brought in the Air by
an East Wind accompanied with Moisture, a little before the Grain is
filling with that milky Juice, which afterwards hardens into Flour.
These Insects deposit their Eggs within the outer Skin (or Rind) of
the Stalks; and when the young ones are hatched, they feed on the
_Parenchyma_, and eat off many of the Vessels which should make and
convey this Juice; and then the Grain will be more or less thin, in
Proportion to the Number of Vessels eaten, and as the Insects happen
to come earlier or later; for sometimes they come so late, that the
Grain is sufficiently fill’d with the said milky Juice before the
Vessels are eaten; and then, tho’ the Straw appear thro’ a Microscope
to have its Vessels very much eaten and torn, and to be full of black
Spots (which Spots are nothing else but the Excrements of those young
Insects), yet the Grain is plump, and not blighted, there being an
Observation, That the early sown Wheat generally escapes this Blight.
And it has been seen, where one Part of a Field is sown earlier than
the other Part, without any other Difference than the Time of sowing,
that the Grain of the latest sown has been much blighted, and the
Grain of the earlier has escaped the Blight, tho’ the Straw of both
were equally eaten by the Insects. Hence it may be inferr’d, that the
Milk in the one had receiv’d all the Nourishment necessary to its due
Consistence, before the Vessels were destroy’d; but, in the other,
the Vessels, which should have continued the Supply of Nourishment
for thickening the Milk, being spoil’d before they have finish’d that
Office, it remains too thin; and then the Grain, when it hardeneth,
shrinks up, and is blighted; yet the Grain of one and the other are
equally plump until they become hard: The Difference therefore is only
in the Thickness of the Milk, that in the blighted being more watery
than the other.
The chief Argument to prove, that these Insects are brought by an East
Wind, is, that the Wheat on the East Sides of Hedges are much blighted,
when that on the West Sides is not hurt: And as to the Objection, that
they are bred in the Earth, and crawl thence up the Stalks of the
Wheat, because some Land is much more subject to produce blighted Wheat
than other Land is; perhaps this Difference may be chiefly owing to the
different Situation of those Lands, as they are opposed to the _East_,
or to the _West_.
Another Cause why some Wheat is more blighted than other Wheat on the
same Land, is, the different Condition in which the Insects find it;
for the Rind of that which is very strong and flourishing[157] is soft
and tender; into this they can easily penetrate to lay their Eggs; but
the Wheat that is poor and yellow, has an hard tough skin (or Rind),
into which the Insects are not able to bore for the Intromission of
their Eggs, and therefore can do it no Mischief. It would be in vain to
advise to prevent the Blight, by striving to make the Wheat poor; for
tho’ Poverty may preserve Wheat from this Blight, as well as it does
People from the Gout, yet that is a Remedy which few take willingly
against either of these Diseases: But this, I think, might be possible
to remedy it, if we could, from the strongest Wheat, take away so much
Nourishment as to turn its Colour[158] a little yellowish just before
the Insects come[159] which I suppose to be in _June_, after the Ear is
out, or at least fully formed.
[157] Some Sort of Land is more subject to this Blight than others;
in such, Lammas Wheat must by no means be drill’d late, and too
thin, lest it should not tiller till late in the Spring; and then,
for want of a sufficient Quantity of Stalks to dispense with all the
Nourishment rais’d by the Hoe, may become too vigorous and luxuriant,
and be the more liable to the Injury of the Blight of Insects.
[158] But this is a very difficult Matter.
[159] Whither those Insects go, or where they reside, from the Time
of their eating their Way out of the Straw, until they return the
next Year, I cannot learn.
Yet this can only be done in wide Intervals; for, unless the fine Earth
can be thrust to some considerable Distance from the Roots after they
are cut off, they will soon shoot out again, and reach it, becoming
more vigorous thereby.
In dry Summers this Misfortune seldom happens, much Heat, and very
little Moisture, being most agreeable to the Constitution of Wheat; for
then its Rind is more firm and hard, as it is, on the contrary, made
more soft and spongy by too much Moisture.
The most easy and sure Remedy, that I have yet found against the Injury
of these Insects, is, to plant a Sort of Wheat that is least liable
to be hurt by them; _viz._ The _White-cone_ (or bearded) _Wheat_,
which has its Stalk or Straw like a Rush, not hollow, but full of Pith
(except near the lower Part, and there ’tis very thick and strong):
’Tis probable it has Sap-Vessels that lie deeper, so as the young
Insects cannot totally destroy them, as they do in other Wheat: For
when the Straw has the black Spots, which shew that the Insects have
been there bred, yet the Grain is plump, when the Grey-cone and Lammas
Wheat mixt with it are blighted. This Difference might have been from
the different times of ripening, this being ripe about a Week earlier
than the Grey-cone, and later than the Lammas: But its being planted
together both early and late, and at all Times of the Wheat-seed
Time, and this White-cone always escaping with its Grain unhurt, is
an Argument, that ’tis naturally fortify’d against the Injury of
these Insects, which in wet Summers are so pernicious to other Sorts
of Wheat; and I can impute it to no other Cause than the different
Deepness of the Vessels, the Straw of other Wheat being very much
thinner, and hollow from Top to Bottom; this having a small Hollow at
Bottom, and there the Thickness betwixt the outer Skin and the Cavity
is more than double to that in other Sorts of Wheat; so that I imagine,
the Insects reach only the outermost Vessels, and enough of the inner
Vessels are left untouch’d to supply the Grain.
This Wheat makes very good Bread, if the Miller does not grind it too
small, or the Baker make his Dough too hard, it requiring to be made
softer than that of other Flour.
A Bushel of this White-cone Wheat will make more Bread than a Bushel of
Lammas, and of the same Goodness; but it gives a little yellow Cast to
the Bread.
Another Sort of lodging Blight there is, which some call _Moar-Loore_,
and mostly happens on light Land. This is when the Earth, sinking away
from the Roots, leaves the Bottom of the Stalk higher than the subsided
Ground; and then the Plant, having only these naked Roots to support it
(for which they are too weak), falls down to the Earth.
To remedy this, turn a shallow Furrow against the Rows, when they are
strong enough to bear it, and when the Mould is very fine and dry;
then the Motion of the Stalks by the Wind will cause such Earth to run
through the Rows, and settle about the Roots, and cover them[160].
[160] Some Land is very subject to the Misfortune of exposing the
Roots, and therefore is less proper for Wheat; for when the Roots are
left bare to the Air, they will be shrivelled, and unable to support
the Plants: And on such Land the Wheat plants have all fallen down,
though in Number and Bigness not sufficient to have produced the
Fourth Part of a tolerable Crop, if they had stood. I am inclined to
believe, that a thorough Tillage might be a Remedy to such a loose
hollow Soil; for ’tis certain to a Demonstration, that it would
render it more _dense_, and increase its specific Gravity: But to
enrich it sufficiently without Manure, the Tillage must pulverize it
much more minutely, and expose it longer, than is required for the
strongest Land: The Fold also will be very helpful on such hollow
Land.
I have never seen any drill’d Wheat so much spoil’d by falling, as sewn
Wheat sometimes is. The drill’d never falls so close to the Ground, but
that the Air enters into Hollows that are under it, and the Wind keeps
the Ears in Motion. Notwithstanding all the Precaution that can be
used, in some unseasonable Years Wheat will be blighted: I have known
such a general Blight, when some of my Lammas Wheat, planted late on
blighting Land, was blighted, amongst the rest of my Neighbours, by
the Insects, but the Grain of the sown Wheat was vastly more injured
than that of the drill’d: The former was so _light_, that the greatest
Part was blown away in winnowing, and the Remainder so _bad_, that it
was not fit to make Bread: The drill’d made as good Bread, and had as
much Flour in it, as the sown Wheat had, that was not blighted; for the
Grains of the drill’d were much larger than those of the sown; being
form’d to have been twice as big as the Grains of Wheat generally are,
had they not been blighted.