The Bridgeport evening farmer., 1917-01-15
POTATO DISEASES
SHOW TENDENCIES
TO TRAVEL ABOUT

Potato diseases, which are show
| ing a tendency to become esta blished
or to spread in various parts Of the
country, can best be controlled in
most cases through the adoption by
farmers of the seed-bed method of
control, according to DR.. H. A. Ed
| son, truck-crop disease specialist of
| the U. S. Department of Agriculture.
| In discussing the potato-disease sit
uation and possible control measures
in a recent address, DR.. Edison said:
"a disease of the potato which is
making it's appearance in several Sec
tons of the country is the one desig-
mated by Orion as streak. The cause
of this disease is unknown. It is
characterized by the appearance OF
angular spots on the leaves, which
have a tendency to run down the veins
through the stems Of the leaflets to
the main petiole, or leafstalk, pro-
ducing streaked appearance. The
affected portions of the plant wither
and die, the leafstalks break over at
the axil of the leaves--that is, their
junction points with the branches
with the result that leaves hang d.
attached only by portion Of the
epidermis. In severe cases the plants
are eventually entirely killed. The
trouble is apparently transmitted
from generation to generation by
means of the seed tubers, and there
is some indication that it is trans
mitted from plant to plant in the field.
In the absence of more definite
knowledge of the disease, it is rec
commended that roguing be practiced
as a precautionary measure wherever
1T appears.
Heavy Loss from Mosaic.
Mosaic is assuming great import
ance as potato disease in certain
sections of the country. It is char
acterized by nothing in the green
Of the leaves, sometimes accompanied
also by crinkling but not a rolling
Of the foliage. The disease should
not be confused with the uneven yell
lowing which results from the appli-
cation of excessive water in irrigated
regions nor with the somewhat diff
ferent yellowing and rolling asso-
ciated with excessive alkai content in
soils, ior should it be confused with
the condition of partial absence Of
coloring matter, possibly chimaera,
seen occasionally in fields, more par
ticu1arly in certain sections of the
West. The cause of mosaic has new
er been determined, but it is known
that the disease is reproduced when
tubers from affected plants are used
for seed. The experimental data
which have been secured both in the
United States and abroad show that
the yield from mosaic plants is less
than that from healthy plants of the
same variety grown under the same
conditions or in the same field. The
average reduction in yield in trials
made by the department with vari-
Gus varieties and in several different
sections of the country is approx
mately 80 per cent. Roguing out af-
fected plants in the seed plot affords
a practical though perhaps not COM
plete control of the trouble.
'"The late blight of the potato caus-
ed by Phytophthora infestans and the
rot of tubers which follows in the
winter are too well known to call for
description. It has recently been
shown, however, that the planting of
tubers affected with Phytophora de-
cay affords a means for infection of
the growing crop. The development
Of the disease, however, is entirely
dependent upon weather conditions. |
In dry seasons one may plant affect |
ed tubers without insuring the de-
velopment Of the late blight, but it |
has been shown that the original in
fections follow up the stems from |
the seed tubers if the weather condi- |
tons are favorable to the develop
,ment of the fungus. It is, therefore, |
advisable to avoid infected seed when |
possible in addition to employing the
usual control by Bordeaux mixture, |
which is a well-esta blished prac- |
tice.
Recent studies upon the powdery |
scab have demonstrated the fact that
this disease is less serious in it's char
acter in the United States than was
at first feared. It apparently un-
able to survive except in the more |
northern sections of the country, and |
the damage done there is, in many |
years, not serious. The disease is |
correlated with heavy, rather wet |
soils, or more particularly with sub |
soils of this character. The damage
done is to a large extent dependent |
upon weather conditions even in these |
unfavorable types of soil.
Decay in Storage
Several species of F'usarium are
now known to produce potato dis |
cases. These may be classified in two |
groups. The first is the wilt-produc-
ing group which attacks the VASCULAR
tissues and the root system of the
plant, cutting off the water supply
and causing injury in proportion to the
extent of the invasion. In extreme
cases q following, or at least an un-
n ealthy green color and character
istic rolling of the foliage develop to
be followed by sudden whiting and
death The tubers produced upon in
fected plants frequently carry the
fungus in their vascular tissue, as
may often be demonstrated by the
appearance of a darkened ring near
their stem end. Infected ..tubers,
stored under unfavorable conditions,
may develop a serious decay, which
is either Of the wet or the dry type
according to the temperature and mois-
ture. The second group includes
other species of Fusarium, which are
to be classified as ground parasites.
They infect the tubers through
wounds resulting from handling while
digging or storing. The infections
may occur in the field or in the .stor-
age houses These forms of decay
may be controlled to large extent
by regulating the storage conditions.