Vermont phÅ“nix. [volume] (Brattleboro, Vt.) 1834-1955, 1890-06-06
AGRICULTURAL.
porAro ROT AND APPLE scAB.
An Experiment stRtisn Bulletin, Des-
cribinE the Causes 81 these Diseases
aud Gtving Remedies.
THE POTATO ROT AND BLIGHT

An Experiment station BuIletiu, Des-
cribinE the Causes 81 these Diseases
asd GIvisg Remedies.
THE POTATO ROT AND BLIGHT.
Judging from the census report the an.
nua potato crop Of Vermont is between .
four and five millions Of bushels How |
much greater it would be were it not for
bug, scab blight and rot, we will not at
tempt to say. 1t is probably an underes-
innate to say that one half Of the crop in
this state was lost last year from blighting
Of the vines and the rotting of the tubers
in the field and cellar.
The weather Of last summer was pecul-
iarly favorable for the development of dis
eases Of this nature, but unless preventive
measures are taken, much loss may be ex
pccted again this season because of the
large amount Of infected seed planted this
spring.
Cause. The blight of the tops" and the
dry rot Of the tubers are both caused by
the same thing, a minute fungus. The wet
rot of the tubers follows the dry rot as
the tubers are weakened or killed by this
fungus. The fungi which cause the vari
GUS rots blights, mildews, rusts, and smuts
Of our plants are themselves plants of a
low order, which live within the tissues or
upon the surface Of higher plants and feed
upon the juices or sap of their hosts If
numerous they thus seriously injure or
even kill the plant they live upon II the
brown tissue Of a potato affected with the
rot be examined under a microscope of
high power the minute thread like branches
or filaments of the fungus that causes the
rot and blight will be found running through
it in every direction. If such a potato be
planted the thread like flaments Of the
fungus grow up in the tissues of the young
sprout and enter the leaves as they are de
veloped In mid summer the fungus pro
duces its spores, microscopic bodies which
correspond to the seeds of higher plants.
These are borne upon minute branches
which are thrust out through the pores of
the potato leaf chiefly on the under side
These spores are produced in immense mum
bers and are so very small, about one thou
sandth Of an inch in diameter, that they
are scattered by every breath of wind If
the conditions of moisture and tempeTa
ture are favorable, they terminate as soon
as they fall upon a potato leaf, and thus the
infection spreads with marvellous rapiditv
1t is often only few days, in some fields
observed last summer only a few hours,
from the time the first indications Of the
blight are seen until all the plants of the
field are backened, decaying mass. 1t is
possible that the blight may spread from a
single diseased plant over the whole of the
largest potato field in the state We will
leave a discussion of the passage of the rot
from the tops to the tubers for future bull
letin, and now speak of treatment to save
the tops from being killed.
Remedies Nothing can be done to kill
the fungus in the plants, but we have great
reason o hope that it is possible to kill the
spores and thus prevent the spread of the
disease from the infected to the healthy
plants. This can be done by spraying with
a mixture of copper sulphate blue vitrio)
and lime known as the Bordeaux mix
ture.' 1t was tried here and at several
other experiment stations last summer and
in all cases proved beneficial The potato
field at the experiment farm was about
three quarters Of an acre in extent The
blight first appeared in one corner of it
and had spread in a diagonal direction
across the field, foiiocing the direction OF
the icind, before any steps could be taken
to check it. The field was then sprayed
with the Bordeaux mixture The work
was begun at one side of the field and the
rows were sprayed for some distance be
yond the middle The next time the work
was begun at the other side of the field and
again continued some way beyond the mid
die The applications " ere made one week
apart number of rows in the middle oil
the field were thus sprayed twice. Nearly
all of the plants at the ends of the field
rotted, while about two thirds of those il
-. Il e IL IL IL
sprayed twice we're saved
1t is necessary TO consider in this connec
ton that the fungus had spread to a con
siderable extent before any spraying va
done and further, that even where sprayed
twice the application was a mild one, sine
only two thirds the amount of copper sui
phate given i'll the directions below wa
used and % gallons was made to exten'
over nearly three quarters of an acre
Judging from this experiment and those o
others made last year, we believe that b.
applying the Bordeaux mixture in time tn
potato rot can be almost entirely prevented
To prepare the Bordeaux mixture, dis
solve six pounds of copper sulphate in l
gallons OF water; in another vessel slak
six pounds of fresh lime in six gallons q
water; when this has cooled, pour it slow
" into the copper solution while stirrin
constantly so that they shall be thorough
mixed.
BY adding Paris green or London purpl
to this mixture the applications for bug
and rot can be made at the same time
One ounce of either is sufficient for ten ga
Ions of the mixture; mix this with litt
water to make a thin paste before putin
it into the mixture otherwise it will
hard to mix them evenly.
The spraying apparatus used in our wor
last summer did not throw a very fin
spray. A force pump with spraying no
zle, such as is used in spraying fruit tree
is the best thing.
The times of application and amour
necessary To give the best results have y
TO be determined by experiment The be
directions that can now be given are
spray with the combination of Paris gree
or London purple and Bordeaux mixtu
upon the first appearance of the pota
bugs, and repeat once in two or thr
weeks until the vines are out of reach
the rot This will require from three
five applications. Experiments are beil
undertaken at the station this summer
see whether less number will suffice.
As copper sulphate costs only about t
cents "A pound, the potato grower can W
afford to make even this number of app
cations if necessary.
tato are now being experimental with,
so, to determine whether the fungus c
be killed in the seed potato without init
ing the termination.
APPLE sCAB.
This is caused by fungus, in much
same way as the potato rot. ExperimeI
made at the Wisconsin and Michigan s.
lions last year indicate that it may be
most entirely prevented by spraying
trees with solution of carbonate of C
per. To prepare the solution dissolve q
ounce of copper carbonate in one quart
strong ammonia. Keep this tightly cork
until ready TO begin spraying, then dill
with % gallons of water. Make the Fl
application as soon as the petals OF
flowers have all fallen, and repeat at int
walls of two or three weeks until mid -su
mer or even later il the latter part Of (
summer be very rainy In applying us
force pump with nozzle that will throw
fine spray, such as is used in spraying
the codhng moth, Unfortunately m
ture of Paris green or London purple W
this solution Injuries the leaves, so that
cannot treat for the scab and the cOdl
moth at the same time. The mixture
the moth lone pound of Paris green or l.
don purple to 200 gallons of water)
safely be applied, however, few hours
ter the copper solution.
Copper carbonate costs about go cent
pound, and ammonia % or 30 cent