The Bridgeport evening farmer., 1917-01-15

stem which originates at the base
where the plant comes in contact with
the parent tuber. During the early
stages of the disease the leaves roll
and the plant assumes a more or less
stunted and bushy appearance. In
other cases the disease progresses less
rapidly SO that the plants may arrive
at full growth without showing evil
dence of infection. In some cases the
disease is confined to the pith of the
stem, not showing at all at the sur
face. Plants affected by this delay
ed type Of black leg produce tub
ers which, however, are more or less
Seriously infected. It Is stock or this
sort which perpetuates the disease.
All Of the evidence accumulated to
date indicates that the bacteria are
unable to live in the soil even during
a single winter. These organisms are
especially susceptible to drying and
are also readily killed on the surface
of seed potatoes by common disinfec-
tants, such as bIchlorid Of mercury.
The 1oguing out of diseased plants
from stock intended for seed Is one
Of the most effective means of con-
trolling black leg. This practice, cou-
pied with treatment of the seed with
bichlorid of mercury according to the
method recommended by Morse, af
fords an almost complete control.
Rhizoctonia and Black Scurf
"Rhizoctonia, the cause Of the we'll
known black scurf of potatoes, is also
frequently responsible for injurious
diseases of the growing plants. 1t is
very generally distributed in all agri-
cultural soils and has recently been
shown to be normal inhabitant of
virgin lands. It's parasitism upon the
potato appears to be correlated with
conditions of environment. Generally
speaking, those types Of environment
which are unfavorable to the potato
and which consequently weaken it's
vitality or lessen its vigor may be ex-
pected to result in increasing the in
jury produced by Rhizoctonia. since
the fungus itself seems capable Of
thriving in all types Of soil and under
all conditions of climate. The most
common type of disease with which
Rhizoctonia is associated are the kill
ing back of thes prouts of young
plants in the spring, which may De
spoken of as a damping off, the pro-
duction of LESSONS or damaged spots
upon the underground stems and up
ers, and lin severe cases the produc-
ton Of a dying of the external It's
sues Of the tuber. The LESSONS upon
the stems are frequently present with
out apparent injury to the vigor Of
the plant or the amount Of yield. The
injury produced is dependent upon the
depth to which these LESSONS kill the
tissue.
''The conducting elements in the po-
tato stem are located in q vascular
ring, the center Of which contains
the xylem, or that portion Of the con-
Quoting tissue through which the ma
terials taken up by the roots are
conducted to the above-ground por-
ton Of the plant. On either side of
the xylen are the phloem strands,
through which the elaborated food
materials are conveyed from the leaves
to the tubers. Whenever LESSONS pene-
trate into the tissues far enough to
produce the death Of these conducting
cells, the communication between the
leaves and the roots is interrupted
and the injury to thep liant is proper
tional to the amount of interruption.
The LESSONS upon the stolons produce
an injury in similar way, cutting off
the communication between the leaves
and the growing tubers, making it
impossible for starch to be conveyed
to them as it is elaborated day by day.
Superficial LESSONS MAKE the deposit OF
starch in the tubers in a normal way
impossible, and frequently result in
the production of swollen internodes
or aerial tubers or the formation of
small tubers on new stolons develop
ed on portions of the stem above the
LESSONS.
Curly dwarf is disease charac-
terized by the foreshortening of all of
the portions of the potato plant above
the ground, frequently accompanied by
a crinkling of the leaflets. The whole
effect is to produce a stunted, more
or less rosetted plant, of which the
yiald IN greatly radanad or franuant-