The Southern herald., 1898-04-01
FARMERANDP PLANTER.
COTTON LEAF RusTs.


The two most common. well-known
and destructive diseases Of the cotton
plant are the so-ealled ''re6 rust and
black rust A third disease, also
very common, but less noticed, is some
times called yellow rust"
Both red and yellow rusts appear
early in the season, often before the
plants ace half grown, but black rust
rarely appears until after the plants
have iiowered. A long study of these
diseases as they appear in central
North Carolina has shown the writer
that both red and yellow rusts are due
to unfavorable conditions Of the soil
and the weather-neyer to parasitic
fungi. sBlaek rust is always due to fun
gus closely related to that which pro-
duees early blight" or "brown ring
spot on leaves Of Irish potato and
tomato plants.
Diseases due to soil or weather are
called physiological diseases. For
these the fungicidal sprays, found so
nseful in orchard or garden, are Of no
value. Although black rust is fun
gous disease, the use Of spray against
1t is not recommended.
The fungus never attacks healthy
leaves, but only those which have been
injured by some other agent. On the
cotton plant black rust always follows
yellow or red rust on the same leaves
and completes the destruction which
the others began. So, il we can pre-
vent red and yellow rust, there win be
no damage from black rust.
Red and yellow rusts are caused
primarily by lack of plant food and
of moisture in the soil. They are most
common and destructive upon old,
worn and dry soils which are lacking
in vegetable matter. Such soils are al
ways deficient in nitrogen and potash
The diseases may also occur on better
soils during very dry aud hot seasons,
and when the soil has been improperly
prepared or the cultivation is wrong.
Red and yellow rusts are nothing
more or less than the premature ripen-
ing of the leaves. When either mois-
ture or inorganic food is wanting, the
leaves dry up, their green coloring mat
ter, ehlorophyl, changes by oxidation
into red or yellow coloring mat.
ter, consisting of carotin and
Xanthophyl respectively. These latter
coloring matters, unlike chlorophYl,
have no power to break up the corbon-
ic acid of the air or to elaborate the
crude sap sent into the leaf from the
root. The leaf itself ceases to be
nourished or to nourish the plant.
The leaf withers and the plant starves,
remains dwarfsh and feeble, setting
none or few bolls. This is where the
damage comes in. The remedy for
these two diseases is partly but not
wholly within the control of the cot
ton planter. 1t may be summarized as
follows:
/. Deep breaking and shallow after
cultivation of the soil, to enable II TO
absorb and retain moisture.
2. Liberal fertilization, especially In
the matter of nitrogen and potash.
3. The restoration of vegetable mat
ter-humus-to worn soils by plowing
in green crops or carting on stable
manure.
4. A more judicious and moderate
use of phosphate fertilizer The
power of acid phosphate to hasten the
maturity of the crop is well known to
all cotton growers. But early crops
and small yield are an invariable
sequence in cotton as well as vegetable
crops.
3. Old worn soils must have their
humus restored by plowing in green
crops or by putting on stable manure.
The best form of concentrated nitro
genous fertilizer for cotton is cotton
seed meal.
The best form Of potash fertilizer is
kainit.
The best form of phosphate is acid
phosphate.
The following formula, originally sug-
gested by the director of the North
Carolina experiment station, has been
widely used throughout the cotton belt,
and on the average upland soil has in
thousands of cases given admirable re
suits:
Cotton seed meal 800 TO 400 lbs per acre
Acid phosphate. ........ 40J TO 500 lbs. per acre
Kainit t.................4 400 to SOC lbs. per acre
NoTE-Soils rich in vegetable matter,
or which have had a crop of clover or
peas turned under, will require less
cotton-seed meal. Soils very poor in
vegetable matter should never receive
more than 400 pounds per acre Of acid
phosphate. In no case should less than
400 pounds of kainit be given 800
pounds is not too much), II a maximum
crop is desired.
For a clover or pea crop use same
formula. without cotton-seed meal.
These crops do not need nitrogen. For
a grain cropgive 50Opounds cotton-seed
meal, 400 pounds acid phosphate and
500 to 900 pounds kainit.-Gerald Nc.
Carthy, Botanist N. c. Experiment sta