The Wisconsin tobacco reporter. (Edgerton, Wis.) 1877-1950, 1914-09-25

NOTE BOOK SKETCHES !
THE BROWN AND WHITE RUsTs.

THE BROWN AND WHITE RUSTS.
From Bulletin No. 2S7, University agricultural
Station by James Johnson.
A common field disease of tobacco in
Wisconsin and one which has given the
growers some concern is the so-called
trust" /" The disease is characterized
by the death of small, usually circular
spots in the leaves of maturing tobacco.
In bad cases these rust spots may run
together, causing large portions of the
leaf to dry and shrivel up. Close ex-
animation of these spots show them to
be made up of concentric rings which
suggest a gradual spread of the disease
from a central point. The trouble US
ually occurs when the plants are from
three-fourths to fully grown and ap-
parently more generally on the bottom
leaves following wet season, and es-
peciallv on low land. This, however,
is not always the case. Brown rust
has been observed on the top leaves in
dry seasons, and on light well drained
soils which tend to disapprove the rela-
tion of excessive moisture to the dis
ease. Close observation of this dis
ease, together with some experimental
work, has yielded little advance in de-
termining the true nature of the
trouble. The writer is inclined to place
this disease among the physiological
disturbances of the plant as no para
site has been found in Wisconsin asso-
ciated with rust spots. The appear
ance of this disease has been attributed
to a number of different conditions
which are ordinarily unfavorable to
plant growth. Some of these acting
singly or in conjunction with others are
undoubtedly influential in bringing
about this trouble, but do not satisfac-
torily explain it. The following are
some of the most important theories as
to the cause of this disease. Rust is
due to:
j l. A fungus or bacterial develop
ment upon the leaf following moist
season.
L2. An excess of certain fertilizers
in the soil.
3. Insufficient moisture while the
plant is in vigorous growth, causing
the leaf to perish in spots from lack OF
food.
4. The use of too much heating
manure followed by period of dry
weather.
5. Excessive moisture in the soil
causing roots to rot, followed by p :
tial starvation of the plant.
6. Deep cultivation cutting the roots
and consequent interference with the
feeding processes.
Z. Over-ripeness Of the plant.
8. Moist weather succeeded by very
hot weather.
9. Drops of dew on leaves acting as
lenses focusing the suns rays and
heating small surfaces to the death
point.
White rust, ''frog eye' or white.
speck" as it is variously known differs
from the brown rust in that the dis
eased areas are smaller and white IN
olor. This rust occurs, occasionally,
on nearly all tobaccos, but causes no
great amount of damage. The spot
was, in fact, formerly considered very
desirable upon cigar wrappers, but up
on the artificial production of similar
spot the natural white speck lost its
value. Since the actual cause of the
rust diseases are not known, no valua-
BILE means of control have been sug-
gested. A wise precaution whenever
practicable is to avoid planting tobacco
in such fields or sections of fields where
rust is known to occur repeatedly to an
injurious extent.