Ottumwa tri-weekly courier. [volume] (Ottumwa, Iowa) 1903-1916, 1916-04-08
Distinction of
Seed Potatoes

The treatment Of seed potatoes with
formaldehyde or with corrosive subli-
mate has been recommended for many
years as a preventive of scab and
other diseases carried on the tubers.
Such treatment Is, on the whole.
profitable, but has several limitations
which should be clearly recognized to
prevent Disappointment, according
to the specialists Of the U. S. De-
partment Of Agriculture. The object
Of disinfecting seed potatoes Is to de-
stroy the germs Of scab and other
surface parasites which might other
wise be planted with the seed and In
feet the new crop. Only surface In
fections are reached by this method.
It is only partially effective against
deep pits of common scab. Formal
dehyde Is less effective than corrosive
sublimate against the black sclerot1a
or resting bodies Of Rhizocton1a or
russell, scab, and against powdery
scab. Neither chemical as ordinarily
used, will destroy silver scurf. Either
one will kill surface infections OF
black-leg, but neither will reach the
internal infections common in tubers
from black-leg hills. Neither fusarium
Wilt nor late blight infection In potato
tubers can be reached by any seed
treatment, nor can any of the non
parasitic diseases of potatoes, such as
mosaic, leaf roll and curly dwarf, be
prevented.
Clearly, therefore, the most impor-
tant precaution against these diseases
10 to select clean, disease-free seed
potatoes from healthy, vigorous plants,
- determined by field inspection dur
Ing the growing season and at harvest.
Seed treatment should then be ap-
piled as an additional precaution. It
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, perhaps ma
tive to some soils. Common scab Is
favored by a neutral or slightly aka
line soil, and seldom gives trouble in
acid soils. 1t Is therefore, increased
by lining and by fresh stable manure,
wood ashes, and alkaline fertilizers,
such as nitrate of soda and ground
bone, while acid phosphate and sui
phats of ammonia tend to diminish
scab.
Sulphur tends to prevent common
scab. 1t Is not substitute for cor
rosive sublimate or formaldehyde, but
Is q good drier for cut seed. Applied
to scab-infested soils at the rate Of
500 pounds per acre it reduces the
scab. but such heavy applications can
not be generally recommended as
Preliminary experimental
trials are advised. .-..
The formaldehyde treatment con-
sists in soaking the potatoes, before
cutting, for two hours in solution
made by adding one pint Of formalde-
hyde to 30 gallons of water. The solu-
ton can be used repeatedly. The gas
treatment II no longer recommended.
Corrosive sublimate is used at the
rate Of $4,000 for u to 2 hours
Dissolve ounces of the salt in hot
water and dilute to IL gallons. This
ID q deadly poison. Use with great
care It must also be kept in wood,
porcelain or glass vessels, as 1t attacks
metal. It Is more effective than for
maldehyde, particularly against Rhi-
xoctonia and powdery scab. Do not
use the same solution more than three
times as the strength diminishes with
each lot Of potatoes soaked.
To treat large quantities, set sew
eral barrels on a slightly elevated
platform. Fit plug in hole in the
bottom Of each barrel, flll with pota-
toes, cover with solution, let stand
two hours. draw off solution and pour
into another barrel. Increase the
number of barrels in proportion to
the quantity to bs treated.