The Dorset County Express and Agricultural Gazette.
Dorchester, Dorset, England, 1861-05-28 00:00:00

Ttgritulturt.

THE TURNIP AND ITS DISEASE.

So largely dependent as we are in the present state
of our crop rotation and system of stock-feeding on the
turnip, it is natural to feel some anxiety- respecting the
disorders to which it is liable, and the 'nudeof cultui
by which it may be rendered most useful. There seems
to be little doubt that these disorders are increasing,
both in number and virulence, and if they do not
threaten its existence as a crop, they at all events
diminish its productiveness. This need not surprise us
when we minsider the very artificial state in which this
root now exists, pushed by so many ingenious appli•
&aces vastly beyond its natural dimensions, and greatly
altered in the relative proportions of its constituent
ingredients. Its constitution must necessarily bare be•
come enfeebled by the abnormal 11101113 of treatment to
which it has been subjected, and not only are its old,
and what may be called its natural diseases, likely to
he thereby aggravated, but new ones are induced to
which it was previously a et rangef.
Yet vastly increased in bulk and productiveness as
the turnip has been, we believe thet we have not nearly
reached the limits to which, in these respects, it is
capable of being brought. We occasionally hoar of
mongers, in regard to size, being exhibited as curios-
ities; what womld the reader think of an entire crop
beieg r into siieh vegetable Lamberts ? It is
out i""s to observe I" Pregressively the weight if the
cusp has increesed since its use began to be getiend till
it has re.telied a general average say of shout thirty
tone per imperial acre. We believe that it is possible,
from what Las beim irleserved iii insulated experiments,
that this weight may be almost doubled, cer*inly very
much increased. It would be interesting, as a matter
of curiosity, to ascertain the maximum which could be
reached—that could be olio point; then the maximum
that could be aimed at consistently with profit. These
two, we imagine, will be found to be by no means coin-
cident. In either CAM doses of guano and other
highly-stimulating manures would be requisite, such as
would astonish the ordinary farmer. Our belief is that
the process could not be carried beyond a certain point,
with any prospect of the extra produce repaying the
extra outlay. In the instances we here seen attempted,
and in which the turnips reached a very large size, the
bulbs, for the most part, became rotten in the heart,
they decayed rapidly after a comparatively slight
attack of frost, and the feeding qualities, even of such
as continued sound, were supposed to be greatly im-
paired. In all such experinients, therefote, the object
ought to be determined what kind of treatment, what
maximum amount of manuring, the land requires to
yield, not the largest absolute produce, but the largest
produee without injury to tic quality of the crop. It
141010 M 1/05Sibla to make a turnip crop too large.
Of all the lIINSOCS that attack the turtup, the one
most deserving of attention is the Finger-and-toe,
whether we regard the extent of the injury, the
peculiar effects it produces or the mystery that sur-
rounds the cause of it. It is certainly not • disease
that has originated, like that of tl.e potato, during the
proves.' of cultivation, or in consequence of the in-
fluence.' of cultivation; for we observe an affection in

wild plants of the same natural order as nearly like it
as the different conditions of growth can be suppoied
to adinit of. In the other cruciferous plants similarly
affected, the nialae.y can be traced to the operations of
iu,ects ; and this of itself affords a strong presumption
that it proceeds from the semi cause in the turnip.
Indeed, of All the views that have been advanced, the
insect theory is the most probable, as it may be regarded
as having lien as nearly demonstrated as such eases
admit of. They are seen in active operation in the
diseased plants, and these operations appear to be
quite adequate to produce the effects we witness,
whether we regard them as emitting a poisonous fluid
which corrupts the juices of the bulb, or simply
causing mechanical injuries which give admission to
the air, rupture the sap-vessels, and thereby disturb
the whole process of vegetable growth. It has been
alleged, in opposition to this view, that the insects do
not attack the plant till after it has shown symptoms
of disease, or at least a tendency to it, which adapts the
plant to the economy of the insect, and that it has the
instinctive perception to select such aues of predisposi-
tion. According to this idea, the disorder must have
an origin altogether unconnected with the insect, and
its presence is owing to the plant having become • fit
Maus for its young, by previous debility or disease
brought on by other causes. These alleged causes are
so manifold and diversified, that it may be presumed
fr 1111 that circuinstance alone that none of them are
_ .

the true one, or indeed that they have any existence.
The soil is pupposed, on one hypothesis, to be deficient
in nutritive ingredients, and that therefore &Uralic, and
alkaline earths are not .present in sufficient quantities
in the plant itself. According to another view, the
soil has la:coined poisoned by the exudation of sub-
stances from the roots of plants ; and again, it is owing
to a general deficiency of plant-food in the soil.
These, and other similar notions, are entirely hypothe-
tical, and have not hitherto received, if indeed they
admit of, any degree of direct proof. The disease ap-
pears in patches in fields where the soil is as Immo-
geneuus as it well can be, and has been subjected to
the same processes of culture and manuring. It pre-
vails in different parts of the country, in soils of almost
every description, and under all diversities of circum-
stances. tioine explanatory cause, therefore, of general
operation is alone adequate to meet the requirements
1 of the case. . . . .

No idea can be more mistaken than that some pre-
vious debility or disease is necessary to make the plant
suitable pabulum for the insect. Particular plenta are
destined to support particular insects, and the latter
make them aubservient to their economy, whether they
are in a state of health or disease. The cases of the
• -13,50 d Ito. rod.fl., doe tpdilo do *bad
Of the turnip bulb fly, and their proceeding,' are well
calculated to illtutratd the operations and effects of the
latter. The two first mentioned of these lay their eggs
on the plants from which they respectively derive
their ounce. The larvae mine their way downwards
into the fleshy roots, and the result is the speedy
decay or death of the whole plant, although not
attended with the peculiar circumstances observable in
the turnip, which are owing to its different configura-
tion and constitution. The moot careful examinatioa,
directed to this very point, has invariably shown that
the must healthy plants are just as liable to the attacks
of the onion and carrot yas such as are weakly,
and that no preference is given to the latter. Their
depredations, too, appear in the same irregular
and uliaccountable way as in the case of the
turnip bulb fly, breaking out in patches here
here and there without any assignable cause, and being
much moreextenaive in some seasons than in others. In
regard to them no previous weakness or incipient
disease is required to invite the insect, and prepare the
plant for its purposes; and there is no reason for sup-
posing that it is otherwise with the Anthernyia of the
turnip. Times mit of number we have found the larva
in the most healthy-looking young plants, before the
effects of its proceedings began to show themselves;
and it is not likely that nature would leave the propaga-
tion if the fly to such an uncertain contingency as find-
ing diseased plants as the only suitable medium of con-
tinuing the species. Cabbage plants are also attacked
by it when they are in • state of entire health and vigor-
ous growth. What has led to the notion, is probably
the fact that insects so frequently riot in putreticent and
decaying substances, and are apt to attack weak and
diseased animas, cases by no means anelagous to that
we are now considering.
It would he somewhat difficult to conduct a series of
experiments so as to show conclusively what share the
fly has in producing the malady. It is a curious fact
that the lam-vets of those caterpillars, which are most
abundant and destructive, are fre.mently so ter° as to
be seldom seen. What can be more col ~,,,, in than the
caterpillar of the gooseberry saw-fly ( NrmatHs (lra:soda-
ritr); yet the fly is rarely observed, and we venture to
say that very few would be able to recognise it. The
game thing may be said of the turnip saw-fly ( Athalia
Spivaraia). Although the black caterpillar may be so
abundant as to be stripping an entire turnip-field of its
leaves, we inay search in vain for the yellow fly that
produces them. Even when the larva of the Anthornyis
were most abundant, we have often not succeeded in ob-
serving a single individual of the mature insece,elzhough
carefully lookedifor in order to watch its proceedings. Ilia,
besides, so like many other common flies.thet it requires
an entomological eye to distinguish it. But if, notwith-
standing these obstacles, • few individuals could be ob-
tained—and this could be best done by rearing the
maggot to maturity, in bulbs kept in the house, when
it would enter on the pupa state, continue no throughout
the winter, and the fly would emerge in spring—(of
both sexes if possible)—early in May, and inclosed under
a gauze cove:ing extended over a few healthy, growing
turnip plants, their proceedings could be witnessed, and
the result would go far to determine the point at issue.
lithe plants fell victims to the disease, as we have little
doubt they would, it might still, it is true, he alleged
that they were predisposed to the malady, and would
have been affected at any rata. But by comparing
two or three patches enolosed in the manner alluded
to with the adjoining portions of the field not experi-
menteel on and if the trials were repeated with
the same or similar result—we might safely rest in the
conclusions drawn as involving the real facts of the
case.
It is certainly a puzzling fact that the disease, if it
his its origin in the cate.e we are disposed to assign to
it, aliould appear in soils in a peculiar physical condi-
tion and in certain localities preferably to others.
But this, as already intimates!, is quite in accordance
with the habit, of other phytophagous insects, and
probably depends on Oduded which we cannot determine.
111 many ,MCA, no doubt, it may be merely accidental,
for these flies have • gregarious tendency, and numbers
may thus be induced to congregate where one or two
happened to settle without any peculiar reasons for
preference. But in obeerving the ways of insects, it
must always be kept in mind that there is much in
theta which we are unable fully to comprehend, and
that they do many things from instinct in which our
reason is not capable of following them:
Even on the supposition that this fly is the entire
cause of tbe finger-and-toe, it is not ea”' to suggest an
effectual remedy. It is vain to speak of quicklime as •
specific—that is, as we understand the term, an
infallible remedy— for the disorder. It certainly acts
as a palliative, but it does nothing morce and the
disease will be found in fields which have been treated
with lime in all possible ways. To catch and destroy
the fly is an impracticable measure, and after the
larva have buried themselves in the fiesh of the turnip.
it would be difficult to reach them with any substance
that would destroy them, and at the bailie time leave
the turnip unscathed. But wherever the plants are
infested to an extent that renders them useless or
nearly so, they should be taken up as speedily as possible,
and subjected to treatment which would kill the
insireot ; and in this was- the multiplication of the fly
might be checked. We have seen diseased turnips
simply piled up in heaps in the field, in which case
the transformations of the insect proceed as readily as
if the plant had not been disturbed. Even if it were
not admitted that the fly in question is the entire or
originating cause of the disease, it is still moat desirable
that its increase ebould be prevented, for noon* will
will deny that it hastens rapidly the decay and
putrefaction of the bulb, and soon renders entirelz
wortblees what might otherwise, even though affected
with the disease, be converted to some useful purpose.
—Scottish Farmer.
L BINIMOLINT INFITITUTIIOII.—It affords
us much pleasure to lay before our agricultural friends
the following notice, taken from the Gardener's
Chroniek of the 18th inst., and in so doing, we would
at the sane time urge upon those to whom it obsefiy
soactirns the deism of tWe society. On the 1,4 May