Montgomery County sentinel. [volume] (Rockville, Md.) 1855-1974, 1906-08-03
AarifmItmtaI.
POTATO sCAB-1Ts PREVENTION

A common idea that potato scab is
produced by chip dirt, ashes or some
thing of that kind is erroneous, says
Director Charles d. Woods, of Maine.
1t is fungus disease that grows from
spores, the same as any other fungus.
Certain conditions favor its growth and
such favorable conditions may be furn-
ished by chip dirt, lime, ashes, etc.
When once introduced into land no prac-
teal way has thus far been found Of re-
moving it, How long it will remain in
the soil is unknown. It certainly may
continue for many years, even when no
potatoes are grown upon the field.
There are many ways in which il is
possible for soil TO become affected. The
germs may be introduced into the ma
nure pile by feeding scabby potatoes to
stock or BY putting them directly into
the compost heap. The fungus may
then propagate itself in the manure, and
if this is applied to the land the disease
may be widely disseminated.
Alkaline soil favors the growth of the
fungus and on this account neither fun
gus nor lime should ordinarily be used
in connection with potato growing, AS
farm manures are slightly alkaline, they
are best not used on potato land
The blowing under Of green crop
tends by its fermentation to make the
soil slightly acid. This condition is I'M
favorable to the growth of the fungus.
There is q more or less common belief
that salt is something of preventive of
potato scab, but exact experiments have
failed to demonstrate this.
Probably the most common way in
which scab fungus is disseminated is by
the use Of infected seed. 1t is, there
fore, of the utmost Importance to use
clean seed. Where it is impracticable
to secure clean seed, or in case of doubt,
it should be treated with fungicide. -
While such treatment will help scabby
seed, it may not act as an entire pre-
ventivo. 1t is therefore best not to use
seed that is much affected.
Formaldehyde gas, either in solution
or in the dry, gaseous state, can be effect.
lively used to clean suspected seed. For
maldehyde Qormalin) is sold in a solu-
ton of about 40 per cent strength and
can be obtained at any drug store.
A few bushels Of potato seed are most
conveniently treated as follows: Make
up a solution of formalin of the desired
bulk, using 16 ounces Of formalin Gao
per cent solution of formaldehyde gas)
to each 30 gallons Of water. Soak the
seed two hours in the solution and then
spread out the tubers to dry. After
drying the potatoes should be cut and
planted in the usual way, but care
should be taken not to allow them to
touch any box, bag or bin where scabby
potatoes have been kept
The Vermont Experiment Station is
studying the treatment of potatoes by
formaldehyde gas, and while they have
not reached perfectly definite oonclu-
sions, they recommend the following
treatment for potatoes in bins:
The bin or room where the potatoes
arc stored should be closed as tightly
as possible. Ten ounces of formalin
should be used for every 1000 cubic
feet Of room, and the potatoes should be
left exposed to this gas "a hours.
The gas is generated by the action of
formalin upon potassium permanganate.
For this purpose three parts by weight
of potassium permanganate are mixed
with eight parts Of formalin in an earth
en- jar. The jar should have a capacity
of about gallon for each pint &c
ounces) Of formalin. The required
amount of permanganate should be
placed in the bottom of the jar and the
needed amount of formalin poured over
it. The operator should leave the room
at once, taking care to close the door
as tightly as possible The retail cost
of the chemical to produce gas for 900
cubic feet will be about $3.50
For handlers of seed who wish to in
sure freedom from scab and for large
growers Of potatoes, this gaseous method
is more convenient than the wet method,
and experiments at the Vermont station
show it to be effective.