The Manchester journal. [volume] (Manchester, Vt.) 1861-current, 1917-05-03
SEED POTATO TREATMENT
Department Of Agriculture Advises
Soaking In Corrosive Sublima,e or
Form maIdehyde.


FormsIdehyde.
The disinfoc,ion Of seed potatoes by
soaking In corrosive sublimate or in
forlnaldehyde is recommended by the
United States department Of agrieul-
turc as q measure that will tend TO
improve the termination and lessen
the danger OF scab.
Such treatment is, on the whole,
profitable, but has several limitations
which should be celarly recognized to
prevent disappointment. The object
Of disinfecting seed potatoes is TO de-
stroy the germs Of seab and other sur
face parasites which might otherwise
be planted with the seed and infect
the new crop Only surface infections
are reached by this method. 1t is
only partially effective against deep
pits Of common scab. Neither corro-
sive sublimate nor formaldehyde, as
ordinarily used, will destroy silver
scurf. Either one will kill surface in
fection of black-leg, but neither will
reach the internal infections common
in tubers from black-leg hills Neither
Fusarium wilt nor late blight infec-
ton in potato tubers can be reached
by any seed treatment, nor can any
Of the non-parasite diseases of pota-
toes, such as mosaic, leaf roll, and
curly dwarf, thus be prevented See
Farmers Bulletin 544 for descriptions
Of these troubles.
Select Disease Free Seed
Clearly, therefore, the most impor-
tant precaution against these diseases
Is TO select clean, disease-free seed
potatoes from healthy, vigorous
plants, as determined by field inspec-
ton during the growing season and at
harvest. Seed treatment should then
be applied as an additional precaution.
1t will not be effective, however, If
the soil where the potatoes are to be
planted is already full of disease.
Soil conditions have an important
relation TO potato tuber diseases, and
many of these are widely spread
throughout the country, and perhaps
native to some soils. Common scab is
favored by a neutral or slightly aka
line soil, and seldom gives trouble in
acid soils. 1t therefore is increased by
lining and by fresh stable manure,
wood ashes, ard alkaline fertilizers,
such as nitrate Of soda and ground
bone, while acid phosphate and sui
phate of ammonia tend to diminish
scab.
Rhizoctonia occurs in some extent
in nearly all soils, but appears to at
tack potatoes most when the condi |
tions are unfavorable to the best de
velopment of the potato plant. Bring
the land to an ideal state Of tilth to
minimize loss from Rhizoctonia.
powdery scab is worst on cold, wet
or poorly drained soils. Black-leg, on
the other hand, is carried by infected
seed. No potatoes showing a deep
brown discoloraton at the stem end
should be planted.
Sulphur tends to prevent common
scab. 1t is not substitute for cor
rosive sublimate or formadehyde, but
is a good drier for cutseed. Applied to
scab- infected soils at the rate of 500
pounds per acre it reduces the scab
but such heavy applications can not
generally be recommended as profit
able. Preliminary experimental trials
are advised.
How to Disinfect Seed
1t is considered better to treat po-
tatoes before they are cut into seed,
if the cut seed is to be very
small. Put into the solution all the
potatoes it will cover and keep the
batch covered by the solution for the
period named under the treatment be-
ing used.
The formaldchyde treatment con-
sists in soaking the potatoes, before
cutting, for two hours in a solution
made by adding one pint Of formalde-
hyde TO 80 gallons of water. The
solution can be used repeatedly. The
gas treatment is no longer recon-
mended.
The corrosive sublimate treatment
Is more effective than formaldehyde,
against Rhiscctonia, or
russet scab, and powdery scab. Cor
rosive suhlimate is used at the rate of
one one -thousandth for one and one
half to two hours. Dissolve two
ounces Of salt in hot water and dilute
10 Is gallons. This is deadly poison. {
Use with great care. II must be kept
N wood, porcelain or glass vessels, as
( attacks metal. Seed so treated must
lot be uEed in the household or left !
shcre animals can reach it.
In using the corrosive subiimatc dip :
I has been found that the solution
weaker each time il is used.