American Falls press. [volume] (American Falls, Idaho) 1907-1937, 1911-04-01
Agricultural Department
PoTAT0E CULTURE.

All arc IauIlIaT with VOtdtO pCuU,
which Is manifest by sOre-like blot
ches on the tuber. 1t is caused by
fungus, the spores OF which trans
NIT the disease. Scab will not de-
yeIop unless the spores are present
either In the ground or on the seed
planted. This would suggest that by
means Of ~disinfectiop. Of the seed
clean potatoes might be grown OF
clean soil. Ii has been demonstrate
! ed that this a be done. However.
the treatment reduces the yield
somewhat.
Scab persists In the soil for a
nu mber OF years; we do not know
how many. 1t is not possible there
for to rid the soil of scab In n or
two years II at all. Without doubt
soil conditions have something to
do with this though just how is not
very well understood. 1t Is a mat
ter OF common observation that the
excessive use OF water tends to in
duce scabbiness In the potatoes.
Particularly is this true II the soil
Is not well drained. The practice of
using deep burrows In irrigation Is
therefore recommended by the 0
successful potato growers. The idea
10 " aRPiy thV Wut0 aOCR CaOboh
SO that the soil In which the 20
.atoes form Is not saturated. The
statement that excess OF water fav-
ors the development of scab is not
without exception though it is rem
orally true. We know of instances
where clean potatoes were produced
In wet soil while elsewhere in the
same field where it was drier, scab
was found on potatoes.
Though scab may persist In a
: field a number of years after pota-
toes were grown there let no one
as a means of avoiding scabby po-
tatoes for experienced potato grower
assert that 1t Is.
When clean seed is planted on ne
land and the irrigation Is well man
aged, potatoes free from scab or
nearly SO are often grown for a
number of years. AS yet potato
scab has o proven a serious
ace to the potato industry, though
the occurrance of bad cases OF scab
are not infrequent.
The fungus. Rhizoctonia. produces
a disease, the different manifesto
tions Of which have been termed
stem rot" "rosette" and little
potato" 1t attacks the potato
and the stem under ground and just
at the surface of the ground. 1t APP
pears as a rot at or just below the
surface of the ground. The plants
affected may die entirely or they
may live through the season. Good
thrifty vines may be found that have
no potatoes or small ones. Such
vines upon examination will be foun
to have a black ring just below the
surface Of the ground, and the stem
under ground may be affected. Small
tuber-forming stems often appear
Just above the point Of injury or in
the axils of the lower leaves. On
the mature tuber the presence of the
disease is shown by small black
bodies varing in size from mere
specks to the size of a wheat berry.
These little bodies carry the spores
which give rise to the disease in
the season following. 1t Is also car
ried over winter in stems that re-
main in the ground and perhaps on
the stems of certain weeds.
The writer has found this disease
all through southern Idaho. To
what extent it reduces yields is not
known, though it is probably quite
considerable. The spore clusters on
the tubers are easily mistaken for
speoks tf dirt Ii any infested tuber
be washed they may be seer more
distinctly, as they do not wash off
but adhere closely.
Infested seed may be treated in
the same way al for scab. A slight
reduction OF the yield attends such
treatments. 1t appears that the only
promising method of over coming
this disease Is by the selection of
tuhers from vines that withstand the
attacks of the fungus and thus bred
pay as there is some expense con-
nected with 1t and the yields are
up n resistant strain Some work
along this line has been done at the
Colorado experiment station and is
giving promise of some valuable re-
suits. 1t Is doubtful IL treatment wi
reduced. The selection OF seed en-
tirely free from the disease is ad-
visable. Seed so selected is likely
to have come from vines that were
healthy and we have reason to be-
lieve that vines grown from such
seed would show a certain degree
of resistance to the disease.
Those growers in Idaho that pro
duce potatoes on a large scale do
not practice any treatment of the
seed Some of the smaller growers,
however, do believing that it pays.
The treatment of seed for both of
the diseases discussed above is the
same. 1t Is especially advisable to
treat the seed where n has new
land or land known to be clean so
as to prevent infection. Having got
ten a start in this way it is an easy
matter to keep the potatoes clean
II true to type by selecting seed
from the best OF each crop. The
treatment consists of soaking the
seed for two hours In a solution Of
80 gallons of water to one pound of
formalin. Dry the seed before cut