Oxford Democrat., 1920-10-26
AMONG THE FARMERS.
"sr.HD TIE pLow."
Pickering Spray or Bordeaux Mixture

Pickering Spray or Bordeaux Mixture
| For moro than twenty five years th,
Maine Agricultural Experiment Station
has been investigating potato diseases
and their control. The late blight
which 10 so often followed by rot was
the worst fungous trouble twenty years
ago. The effectual control of this dis.
ease was shown to be practicable by the
thorough application of properly pre-.
pared Bordeaux mixture. The efficiency
of Bordeaux mixture depends upon the
copper that IL carries. When In 1910
the price of copper sulphate rose 60
greatly the Federal Bureaus of Chemis.
try and Plant Industry in cooperation
with the Maine Station began studies
looking toward lower cost fungicide
than Bordeaux mixture. Previous In
vestigations had failed to discover any
fungioide which could replace copper
sprays for late blight of potatoes, As
the search for new spray seemed I'M.
promising 1t seemed advisable to seek
for q copper spray which should be
more effective per unit OF copper than
the standard Bordeaux mixture and at
the same time not sufficiently caustic to
injure foliage.
A spray to be effective must 80 dis
tribute the copper compound 1t contains
as to completely cover the leaves of the
potato plant In thoroughly uniform
manner and must possess the proper
adhesive qualities. Lacking either of
these qualities the spray fails to protect
the plant from the fungus.
Lime is only slightly soluble 10 water.
When quick lime is Stacked with an
abundance of water and is allowed to
stand most of the Stacked lime settles to
the bottom. The water above this will
however contain small amount OF lime
in solution. This solution is made and
sold at drug stores as "Lime water"
thoroughly 1t is mechanically suspended
in the water and is known as "Milk of
Lime" Bordeaux mixture is made
from dissolved copper sulphste and the
milk of lime. At the Woburn England
Experiment Fruit Farm they tried max
ing spray with copper sulphste and
lime water. These were called from
the name Of the investigator, Pickering
sprays, and limited work in England
showed them In some particulars supe-
rior to standard Bordeaux mixture made
with the milk of lime. 1t was claimed,
and corroborated by other investigators,
that Pickering sprays remain in suspen-
sion far better and longer than standard
Bordeaux mixtures, that they have a
larger covering capacity, that the film
on the foliage does not deteriorate as
fast as that from standard Bordeaux,
that it acts more quickly, Is free from
gritty particles. On the other hand as
tried out in Victoria (Australia) the
Pickering spray was found inferior to
2 per cent standard Bordeaux mixture.
With all these more or less conflicting
data and with the thought in mind that
II the results obtained by Pickering un-
der laboratory conditions in England
would hold true under American field
conditions great saving in copper
would result, the Investigation by the
Federal Department of Agriculture was
planned In cooperation with the Maine
Station. The experiments were con-
Quoted with the following primary OBJ
jects: To determine whether Pickering
sprays were effective when applied to
potatoes under Maine field conditions.
To ascertain how much copper 10 re-
quired In the Pickering sprays to insure
effective control of late blight. To COM
pare the fungicidal value OF the Picker
ing sprays with standard Bordeaux mix
ture per unit of copper; to determine
the amount Of foliage injury from the
Pickering sprays as compared with
standard Bordeaux and to compare the
adherence of Pickering sprays with
standard Bordeaux.
The results of these studies have been
published In the technical bulletin 868
of the United States Department OF
Agriculture. This bulletin is not avail
able for general distribution. The fol-
lowing is a brief summary of the results:
In the ordinary $3.50 Bordeaux there
is about 1.25 per cent of copper present.
In the most effective Pickering solution
there is Z per cent copper present.
In three seasons work In the control
of late blight on potatoes Pickering
spray containing Z per cent of copper
sulphate controlled the late blight as
well and gave yields equal to those OBJ
tanned with 8 5 so Bordeaux containing
1.25 per cent copper sulpbste. The cop.
per in the Pickering spray was appar-
emily, weight for weight, nearly twice
az effective as that In the standard BOr.
deaux. There was no injury to the
vines of tubers from any of the sprays
used in the experiment. The Pickering
spray Is not conspicuous on the foliage
but from chemical examination of the
leaves 1t was found to adhere better
than Bordeaux. The addition of rosin-
fish.oil soap did not improve the adhe-
sive properties of the spray.
By the use OF Pickering spray tho
amount of copper needed to protect the
potato crop in Maine could be reduced
more than 40 per cent. Also Pickering
spray requires less lime. 1t is not sug-
gested that Pickering spray be used by
all growers but the more careful men
could doubtless reduce the cost OF spray
ing very materially by substituting II
for standard Bordeaux. It not only
takes less lime and copper, but 1t con-
tains no coarse particles to wear the
spray apparatus and clog nozzles. And
Il is probable that more nearly proper
Pickering spray would be made by the
average man than is the case with Bor-
deaux mixture.
To any one who may care to try Pick.
ering spray In 1921 for the protection OF
potato vines from late blight the Maine
Station will on application send direc-
tions for It's preparation. 1t does not
involve any added containers and the
copper stock solution is the. same In
both Bordeaux and Pickering sprays
Chas. D. Woods, Director.