St. Johnsbury Caledonian. [volume] (St. Johnsbury, Vt.) 1867-1919, 1894-07-12
CONCERNING PorATo BLIGHT.


Botanist L. R. tones of the State
Experiment Station at Burlington
has issued another circular in re-
Spouse to many inquiries concerning
potato blight and how to deal with
it. He says:
Our potato vines are attacked by two
distinct blights. The early blight at
tacks earlier potatoes, spreading slowly
in July and August, causing premature
death of vines but no rot. The late
blight attacks later potatoes in August
and September, spreading rapidly in
warm, moist weather, and is followed
by rot. The early blight is a complex
trouble caused by the attacks of insects
as we'll as fungi. 1t is already appearing
on early potatoes. Being a complicated
disease, it is less perfectly controlled by
spraying than is the late blight. Our re-
suits last summer showed that it can be
at least partially checked by Bordeaux
mixture. The late blight and rot is a
fungous disease, and Bordeaux mixture
properly applied is an almost perfect
remedy. BY its use we have invariably
kept our later potatoes alive through
September and have lost but very few
from rot. The result has been that our
yield of later potatoes has been more than
doubled by spraying. Every potato
grower should try it this summer, especi-
ally on medium and late potatoes.
The formula for Bordeaux mixture is :
Five pounds copper sulphate, FIVE pounds
lime, Unjust be fresh, not air slacked),
fifty gallons lone barreD water. Dis
solve the copper sulphate in clean wood
en- or brass vessel, slack the lime in an
other vessel, then dilute with water to a
IL. Il. Il.
copper solution. Stir thoroughly and
add water to make about fifty gallons
Zone barreD.
The following suggestions may prove
of use:
1. Keep your mixture clean. Chips,
Jumps of lime, etc. in the mixture will
clog pump or nozzles. Therefore, thor
oughly clean all vessels to begin with.
Strain all water and copper solutions
through cheese-cloth unless they are per-
fectly clean. Strain the lime whitewash
through some coarser cloth or sieve and
throw away all the dregs and Jumps.
2. To dissolve blue VitrioI 1t may
be quickly dissolved in water by heating
in brass kettle to the boiling point, or
by pouring boiling water over it. The
most convenient way we have found,
however, is to dissolve in cold water by
putting it in coarse sack and suspend
ing this in the top of tub or barrel of
water. As fast as the heavy solution
forms it settles to the bottom and fresh
water rises. By using a gallon of water
for each pound of blue vitriol it will dis
solve in a few hours in this way.
8. Keep a stock solution. We find it
most convenient to dissolve considerable
blue vitriol at time in the above man.
ner, and to keep it on hand in covered
barrel. We put in pound of vitriol for
each gallon of water, and as we wish it
from time to time we simply stir it up
and dip out as many gallons of the solu-
ton as we wish TO use pounds of blue
vitriol.
+. Other convenient methods. To
avoid the trouble of weighing the blue
vitriol may be measured out five pounds
equals two quarts), and the lime added
by test. The test consists in pouring a
few drops of solution of ferrO-cyanide of
potassium Zone ounce in four ounces
water into the mixture. If there is not
enough lime in the mixture this solution
will at once turn brick-red, but if enough
lime has been added there will be no
change Of color.
3. Caution. Strong copper sulphate
solution alone will kill the leaves. Fresh
" Stacked lime neutralizes the sulphate
and prevents this CauStic action. If not
sure that the lime is fresh or good, or
that enough is added, the mixture should
be tested as described in +, or a few
plants only should be sprayed at first TO
test its action.
6. Potato beetles. Bordeaux mixture
alone will not kill the potato bugs. Add
paris green when needed at rate of one
half pound to fifty gallons.
Z. When to. spray. Remember that
Bordeaux mixture is a preventive, not a
cure, and the first application should be
made before the disease appears. The
following dates tor spraying potatoes are
based on our experience at Burlington:
Early potatoes planted April to May
5-spray about July /, Is, August L, and
again if needed.
Medium potatoes planted May 3 to
May 15-spray about July 10, August 1,
Is and again if needed.
Late potatoes planted May Is or later
spray about August l, Aug. IA, Aug.
% and again if needed.
s. How to apply it. The mixture may
be put on in any way so as to cover the
upper surface of all the leaves. The best
way to do this is with a force pump
which has good spraying nozzles attach
ed. Unfortunately, but few have these
pumps. Applying with a common wa
tering pot or with pail and broom o.
wisp of hay takes more time and patience,
as well as more of the mixture, bat If