Daily Kennebec journal. [microfilm reel] (Augusta, Me.) 1870-1975, 1917-11-29
P0WDERY SCAB
Influence of Tempera-
ture and Moisture on
It.

Orono. Me. Nov. 27.-The following
was issued today from the office of
Charles D. Woods, director of the
Maine agricultural experiment station
at the University OF Maine:
In a recent letter of this series il
was pointed out that powdery scab of
potatoes is seldom of much conse-
quence on the better types of potato
soils in Maine. that there is little or no
likelihood of the disease spreading to
the sections OF the State where it is
not now known TO occur. and that 1t
need not he feared farther south where
Maine potatoes are used for seed pur-
poses.
The last two statements in the above
paragra phi are based upon field obser-
vations and experience in this State
and in other parts OF the country. IT
i evident from these observations that
relatively slight variations in soil tenn
perature and moisture. even if the UNI
favorable conditions occur for short
periods OF time in an otherwise favor
able season or climate. prevent the de-
veloYnent Of the disease. Apparently
also .. climate where the soil tempera-
ture and moisture conditions are nor
nally unfaICrahle is 1ata! to the pow
derr scab organism itself.
Last winter and spring an attempt
was made by one of the pathologists of
the Maine Agricultural Experiment
Station, to test, by means of a green
house experiment under control con-
ditions. the validity of these conclu
sions arrived at as the result of more
or less general field observations. The
experiment was, of necessity, con-
Quoted on a very limited scale. 1t is
felt, however, that this was more than
offset by the fact that in the green
house the temperature and moisture
conditions were at all times under the
direct control of the observer and We're
constantly maintained during the
growing season of the plants.
In the experiment in question soil
which was infected with the germs of
powdery scab, and which had just pro-
duced crop of badly diseased tubers
was placed in large flower pots. In
each pot was planted Single, disin
fected tuber known to be free from
powdery scab infection. All of these
potatoes planted in pots of infected soil
were kept under normal conditions of
temperature and moisture till germi-
nation had started and the green
sprouts We're showing above the sur
face. They We're then divided into
three lots and placed in separate rooms
having carefully regulated day tenn
peratures of 60. 10 and 80 degrees T.,
respectively. The night temperature
in each room was relatively lower and
these differences We're maintained as
constantly as possible till the potato
plants in the pots We're mature and the
tubers they produced were harvested.
In addition the pots in each room were
again subdivided into three lots ac-
rording to the amount of water sup
piled \ part We're kept as dry as
practicable ana vet have the plants
grow. To represent !, dry season: a
part were given a medium amount OF
moisture. representing a normal sea =
son: and the remainder We're kept
heavily Watcrcd throughout the ex-
pertinent. to represent a wet season.
1t viii h., s,"rH. then. that three differ
rnt temperature conditions We're pro-
Vided and, under each. potatoes We're
grown with three different. constant
supplies of moisture
\ careful examination of all OF the
tubcrs produced in each pot was made
At harvest time. The only powdery
&cab found was from plants grown in
the rOO room and in the pots in this
room receiving abundant or normal
amounts OF water. Pots with the re
qLired amounts of moisture with the
temperature too high did not show in
lection even in the slightest degree
ture but with the moisture content
lacking did not ssoW infection. This
experiment, made under control con-
ditionS seems to Indicate. as do gem
eral field observations and expert
enCe, that a cool. moist season or
climate is favorable to the develop
ment of the powdery scab organism.
and that it Will not develop to any
marked extent. if at all under any
other conditions. Summer tempera =
lures aud moisture conditions which
prevail over a large part Of the coun-
TN prevent the spread of the disease
to other parts of the United States ana
explain its restricted distribution in
the State # Maine.