The gazette-times. [volume] (Heppner, Or.) 1912-1925, 1914-06-11

Q Q o . o o o o o o o o o o Q o
By o. M. MORRIS, Horticulturist; ]. G..
HALL, Plant Pathologist, and M. A.
YOTHERS, Asst. Entomologist,
at Washington Experiment
Station.
HROP rotation will often reduce the
~ amount of disease in an infected
field, but the periods of rotation
should be longer than three years. The
collection and burning of the tops upon
diseased field will decrease the amount
of the fungus upon that field and tend
to diminish the amount Of disease.
''Rosette," Little Potato"
The "Rosetten or "Little Potato"
is often introduced into section with
the seed potatoes These diseased tub
ers have upon their surface dark brown,
irregular patches of the fungous threads
These are most easily seen if the tuber
is wet. When these diseased tubers
are planted the young shoots are early
attacked by these threads upon the
tuber causing black spots upon the
stems near the surface of the ground.
Sometimes the stem is completely
girdled by disease. The fungous threads
spread to the underground parts Of the
plant and may proceed upward above
the surface and form grayish white
layer around the stem. The effect of
this layer is to cut off the supply of
food that should 60 to the tuber and
thus cause the formation Of small aerial
tubers upon the stem above the ground.
Where the disease does not SO affect
the plants the tubers under ground are
affected and their surface may become
more or less covered with the rusting
stage Of the disease.
The effect upon the plant is very
marked at times, causing the nodes to
become shortened and so producing the
so-called "Rosctte
Treatment Is Told.
The shortening Of the stem and the
consequent rosetting Of the leaves is
accompanied by the rolling of the leaves
inward and upward, especially in the
middle of the day. This often results in
tip burn because of the inability Of the
leaves to return to their normal posi-
tion before they are exposed to the sun
the following day
Since the principal means of spread
of the disease is through the use of in
fected seed, all treatment must be d.
rected toward preventive measures, as
in the ease of the scab Clean seed and
only clean seed should be planted If
there is any doubt as to the seed being
clean and free from the disease it must
be treated as for the potato seab.
Infected tops and tubers should be
removed from the field and destroyed
by fire. Soil badly infested should not
be planted to potatoes, but such soil
may be made to produce fairly good
crops by lining, clean culture methods
and crop rotation.
BLACK Leg
Potato plants affected with "Black
Leg" are usually readily seen in the
field by careful observer They ap-
pear more or less unhealthful and some
what undersized, according to the Sc
verify of the attack. The branches and
leaves have tendency to grow erect
and not spread out as much as usual,
thus giving the plant top more COM
pact appearance Later these plants be-
come lighter in color and die. The dis
ease is certainly known by the black
ened' stem below the ground, although
the color may extend in some cases two
or three inches above the surface. U.s.
ually the seed tuber from which the dis
eased plant grows is found to be decayed
with a soft rot and may have disap-
peared entirely.
First, select clean seed; that is, seed
from fields that are not infected. Sec
ond, discard all potatoes that show
wounds, cracks, or decayed areas. Third,
treat all seed before planting with for
malin--one pint to 80 gallons of water
for two hours.
Diseases Rare or Unknown.
The following potato diseases are
either unknown in the state or are of
M serious import M yet. but may be-