Oxford Democrat. [volume] (Paris, Me.) 1833-1933, 1904-10-18
The Time to Dig Potatoes.

The Time to Dig Potatoes.
Aside from the necessity of supplying
the markets and home table, which leads
to the prompt digging of early potatoes,
the problem of early or late digging OF
the main crop of late potatoes largely
hinges en- the relation of the late blight
to the rotting of the tubers in the ground
and in storage. CONTRARY to wide.
spread belief, late digging will be found
to give the greatest freedom from rot, as
will be shown later in this article. y
Ii is much to be regretted that the
practice of spraying with Bordeaux mix
ture for potato blight does not become
more general. 1t has been repeatedly
proved an effective and profitable RENE
dy, and will not only increase the yield,
but will also prevent the dry rot that
follows late blight. Many if not most
farmers have not sprayed, however, and
are now confronted with the danger OF
loss from rot, for throughout the great
tato-growing sections of this country
late blight has long prevailed so general
ly that it is the exception for late varie-
ties to remain green until frost or until
their natural maturity.
The disease varies in the time OF its
appearance in accordance with the
weather conditions. In bad years growth
is cut off early in August, but the more
usual time is the last of August or first
week in September, when the tubers are
making their most rapid growth in size.
The further loss from rot is greatest in a
warm, wet autumn, and least when the
weather is dry.
The common dry rot of the tubers is
caused by the same fungus that pro-
duces the late blight of the foliage, and
potatoes in blighted field are literally
infected with the disease. There is
little evidence to show that the fungus
reaches the tubers by direct growth
through the stem. 1t is more probable
that the spores are washed down through
the soil by rains. The fungus in at
tackiug the tubers is providing for its
preservation through the winter, for as
far as We know this is its only means of
living from fall to summer.
To prevent loss from rot, 1t has often
been argued that potatoes should be dug
as soon as the tops were killed, and it
has even been recommended that dig
ging should take place as soon as the
first signs of disease are noticed on the
leaves.
Until recently the general advice has
been to dig early, the idea being to lessen
the danger of infection from the spores
of the rot fungus, and to put the tubers
in a dry place, where it was supposed
that the conditions would be less favor
able TO the development of rot than in
the damp earth. This advice was not
based on actual field trials, however,
and as far as the writer is aware, no
experimenter dug potatoes from blight
ed fields on different dates and carefully
comp..red the loss from rot, until two
wears ago, when Prof. l.. X. Jones be-
gan series of tests at the Vermont Ex-
pertinent Station, the results OF which
have reversed our former opinions by
showing that the loss is least when po-
tatoes are left in the ground for some
time after the tops are dead.
He had potatoes dug as soon as traces
of disease were observed, and again at
intervals of a week, until the stalks
had all been dead two or three weeks.
These different lots were stored care
fully as soon as dug, and after the last
were dug on Sept. rs, the number OF
rotten tnbers was determined. Those
dug early when blight first appeared had
over 80 per cent decayed, while those
dug ten days after tops were all dead
had only I per cent decayed. The total
yield of sound tubers from the rows dug
late was over double that saved from the
rows dug early. This experiment has
been tried for two years with the same
results, and there is no doubt about the
correctness of the results. This is a
matter of the greatest Importance to our
farmers, many of whom suffer great loss
from rotting in storage, which might be
partially avoided by later digging,
Prof. Jones has done great service to
agriculture of this addition to our know
ledge.
The explanation of this matter will
undoubtedly be found after closer
study of the lfe-history and require
ments of the fungus that causes potato
rot. Prof. Jones considers it probable
that when potatoes are dug and stored
early, the conditions are such as to up
set the balarce between the potato and
the fungus. The high temperature OF
early fall and the sweating of the tubers
hasten the action of the engines that
take part in the natural ripening of the
potato, and also stimulate the growth OF
the fungus.
Whatever the explanation is, the fact
is established that early digging tends to
promote rot in storage, and that the best
policy is to leave the potatoes in the
ground for ten days or more after the
tops decor. in Country Gentleman.