The Washington times., 1917-04-02
POTATO SEEDLINGS
NEED DISINFECTING
Selection and Treatment With
Corrosive Sublimate or For
maldehyde Important.

that many Washingtonians plan to
raise that vegetable this season. II
potato raising IL to be made a sue
cess, particular care must be used in
selecting and treating the seedlings
The disinfection OF seed potatoes by
soaking in corrosive sublimate or in
formaldehyde is recommended by the
Department OF Agriculture to improve
termination and lessen danger of
scab.
Such treatment is profitable, but
has several limitations which should
be recognized. to prevent disappoint-
ment. The object OF disinfecting
seed potatoes Is to destroy the germs
of scab and other surface parasites
which might infect the crop. Only
surface infections are reached by this
method. 1t is only partially effective
against deep pits OF common scab.
Neither corrosive sublimate nor
formaldehyde, as ordinarily used, will
destroy silver surf Either one will
kill surface infections of blackleg,
but neither will reach, the internal
Infections common In tubers from
blackleg hills. Neither-fusarium wilt
nor late blight infection in potato
tubers can be reached by any seed
treatment, nor can any of the nom
parasitic diseases Of potatoes, such as
mosaic, leaf roll and curly dwarf
thus be prevented. Farmers Bulletin
GA describes these troubles.
Select DIsease-Free Seed.
Clearly, therefore, the most I'm
portant precaution against these dis
eases is to select clean, disease-free
seed potatoes, from healthy. vigor-
Gus plants, as determined by field in
spection during the growing season
and at harvest. Seed treatment should
then be applied as an additional pre-
caution. It will not be effective, how
ever. II the soil where the potatoes
are to be planted is already full of
disease.
Soil conditions have an Important
relation to potato tuber disease, and
many of these are widely spread
throughout the country, and perhaps
native to some soils. Common sca6
Is favored by a neutral or slightly
alkaline soil, and seldom gives trouble
in acid soils. 1t therefore Is increas-
ed by lining and by fresh stable
manure, wood ashes, and alkaline fer
tilizers, such as nitrate OF soda and
ground bone, while acid phosphate
and sulphate of ammonia tend to di-
minish 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.
Powderly scab is worst on cold. wet.
or poorly drained soils. Blackleg, on
the other hand. Is carried by infected
seel. No potatoes showing a deep brown
discoloration at the stem end should
be planted.
Sulphur tends to prevent common
scab. II Is not a substitute for corrosive
sublimate or formaldehyde. but Is
good drier for cut seed. Applied TO
scab-infected soils at the rate OF 600
pounds per acre II reduces the scab.
but such heavy applications cannot gen.
orally be recommended as profitable
Preliminary experimental trials are ad-
vised-
How to DIsInfect Seed.
1t Is considered better to treat pota-
toes before they are cut into seed. es-
pecially II the cut seed Is to he very
small Put into the solution all the po-
tatoes It will cover and keep the batch
covered by tia solution for the period
named under the treatment being used.
The formaldehyde treatment consists
In soaking the potatoes. before cutting.
for two hours in a solution made by
adding one pint of formaldehyde to thir-
ty gallons OF water. The solution can
be used repeatedly. The gas treatment
is no longer recommended:
The corrosive sublimate treatment
Is more effective than formaldehyde,
particularly against rhizoctonia, or
russet scab, and powdery scab.. Cor
rosive sublimate is used at the rate
OF 1000 for one and one-half to two
hours. Dissolve two ounces OF the
salt in hot water and dilute to fifteen
gallons. This is a deadly poison. 1t
must be kept in wood, porcelain, or
glass vessels, as II attacks metal.
Seed so treated must not be used in
the household or left where animals
can reach 1t.
In using the corrosive sublimate
dip II has been found that the solu-
tion becomes weaker each time II Is
used. The degree to which the dis
lnfectant is taken out OF the solution
varies according to the amount of
dirt on the potatoes: the character
OF the water, and the kind of con-
tainer. For practical purposes II will
be sufficient to add one ounce of dis
solved corrosive sublimate to each
thirty gallons OF solution after each
batch OF potatoes has been treated.
When this has been done four times
throw away the old solution and pre-
pare new solution.
Seed potatoes may be treated sew
eral weeks before planting, provided
they are not reinfected by storing in
old containers or storage bins.
Sprouted potatoes are injured by
treatment, but will throw out new
sprouts. In general, however, pota-
toes will not be injured by following
directions. Many growers believe
termination is improved by treat