Alma record. (Alma, Mich.) 1878-1928, 1916-06-08
ABOUT SEED POTATOES
BY NJ. A. c. Bulletin, No. 3

/. Can potatoes from fields which
were affected with late blight safely
be used for seed?
Potatoes which did not develop
large amount of late blight rot in
storage if carefully sorted so that
practically all of the tubers which
show any external or internal eidence
of late blight have been removed, can
be used for seed. Potatoes from fields
which were not blighted will be safer
for seed but are not always available.
If the potatoes are clean and the
skin bright, it is not difficult to sort
out the tubers affected with late
blight If they are dirty or the skin
F, is dark and rough, il will not be an
easy matter to detect all of the tubers
which have blight producing organ
quite certain that practically all
blight-carrying potatoes have been re-
moved, it will be best to secure other
seed.
Seed potatoes which have blight
organisms in them will either produce
no plants or weak plants. Such tubers
will also become the source of infec-
ton for the late blight if the weather
conditions are favorable for the de-
velopment of the disease.
The external evidence of late blight
-, h t,,horg - tho fret Of ttc
development is brownish discolora-
ton of the skin in irregular shaped
spots which vary in size. These spots
increase in size and become somewhat
sunken as the disease develops. In
ternal evidence of late blight in the
tubers is shown by brownish discolor-
alton of the flesh in areas correspon-
ding in size and shape with the exter-
nal spots and extending below the skin
to a depth of one-eighth inch or more.
In the later stages of the disease, the
tubers become shrunken with dry rot
or decay. The odor from potatoes
which have decayed with soft rot as
the result of the late blight is very
offensive.
2. Should potatoes be planted in soil
where potatoes blighted the previous
season?
1t is not advisable to plant potatoes
in soil in which potatoes were grown
the previous season whether late
blight was present or not.
1t has been quite certainly proven
that late blight does not live over win
ter in the soil, except occasionally
on blighted potatoes which escape
freezing. Scab, Black Scurf (Rhizoc-
tonia) and Fursarium Wilt do how
ever, live over in the soil from one
season TO another and are for that
reason likely TO cause more damage
when no rotation is followed than
when there is change of crops. Fur
thermore, rotation of crops, espec-
tally when clover precedes the potato
crop, will keep the soil in much bet
ter condition for potatoes than it will
be when potatoes arep lanted on the
same soil one season after another.
i 3. Should potatoes from vines which
were killed by an early frost be used
for seed?
Early freezing of the vines will not
injure the tubers for seed purposes,
except that will reduce the yield. if
the potatoes grow to be as large as a
hens egg or larger. 1t is a common
practice in the South to plant potatoes
for seed so late that the vines are
green when killing frosts occur. These
so-called Second Crop potatoes are
considered superior for seed purposes
to those planted earlier in the season.
4. Should frosted tubers be used for
seed?
In no case should tubers which have
been frosted be used for seed. Po-
tatos which have been chilled if used
for seed will give a poor stand. If
there is a suspicion that the potatoes
may have been frosted but evidence
does not show on the tubers, it will
be a good plan to place number of
them in the greenhouse, hotbed or a
sunny window in a warm room and
test their terminating ability. If a
number of the sprouts make a weak
growth the potatoes should not be us
ed for seed.
3. How can seed potatoes be kept
in good condition until planting time
Seed potatoes stored in cold storage
or in well-located and properly con-
structed potato cellers or pits will
usually keep in good condition until
time to plant.
When the temperature in the stor-
age place begins to rise in the spring
and there is danger Of the potatoes
sprouting considerably they can be
kept in good condition by removing
them to a barn floor or other large
space where the tubers can be spread
y.