The gazette-times. [volume] (Heppner, Or.) 1912-1925, 1914-07-30
- HIZOCTONIA or little potato dis.

the exception of the late blight the
most serious disease of potatoes in
Western Washington. 1t is widely dis
tributed in the United States, Europe
and Asia and is of wide interest. It
has been known in Europe since 1851
and was first described in America in
1891. 1t seems to be general on the
Pacific Coast and is certainly prevelant
in Western Washington, causing losses
last year as high as so per cent in some
fields.
Symptoms-There are several char
acteristic symptoms Of this disease, some
Of which however may be the result of
some other cause. When the plant is
attacked the stem is affected at the
ground, showing as black discolorations
and may girdle the stem for a half to
IN inch above the ground. A gray,
moldy growth appears on this area. A |
discoloration exactly like this results
from an attack of the black leg disease
but is not accompanied by the gray,
moldy growth. If the attack Of the
Rhizoctonia disease is serious the stem
is rotted and the top Wits and dies
early in the season exactly as is the ease
with the black leg and Fusarium dis
ease. However, with the latter the dis
ease is not evident on the stem, the
leaves roll and the plant may or may
not be killed at this time.
When Attack Comes Later.
If the attack of Rhizoctonia is not
severe enough to kill the plants, or the
attack comes on later in the season as
is usually the case in Western Washing
Ton, only the outer part of the stem win
be killed In this case the diseolora-
tion and the gray moldy growth appear
but the plant remains alive. The tops
usually develop peculiar twisted leaves
with the leaves crowded together in a
compact rosette-like appearance, not
found associated with any other potato
disease Aerial tubers-small potatoes
on the vines-are formed and the pota-
toes in the hill are small and very
numerous. This is caused by the grid
ling of the outer part Of the stem at the
ground.
The raw ford material from the roots
ascends On the inside of the stem to the
leaves where it is manufactured into
starch. But because the starch can only
descend on the outside of the stem to
reach the roots and tubers, and since this
part is dead at the ground and prevents
thedescent of the starch, the starch col
leets on the vines and forms little po
tatoes Since little food reaches the
tubers in the soil those developed there
are small and numerous.
Attacks Of Dlack Leg.
Attacks of black leg result in mucl
the same way except that it kills tn
plant early and only few tubers de
velop either on the vines or in tn
ground, and those in the ground are usu
ally rotted at the stem end. If the plan
is alive late in the season and tte tuber
are numerous and not rotted at the ster
end the Rhizoetonia oisease has in a
probability caused the trouble.
This disease causes the formation G
q network of fine, hairlike, brow
threads on the surface Of the tube
which may or may not be large enoug
in diameter to be visible to the make
eye. These can only be observed, hoy
ever, as the tubers are maturing and n,
after digging. At digging time the di
ease shows as brown, superficial, eleva
ed irregularly shaped masses, varying
size from a small dot to spot as larl
az quarter of an inch wide and ha
an inch long These may be mistake
at first for soil PARTICLES but upon ru
bing they will be found to adhere.
washed these masses are found to
dark brown and adher1ng with ten
city which necessitates hard scrubbil
or picking to get them off. Either
these last two symptoms are peculiar
this disease alone and their presence is
positive means of Identification. II
disease as far as is known does not fl
ther affect the potato except that the
are indications that it may spread