VOL. XXIV.
INDIANAPOLIS, IND., SEPT. .7,1889.
NO. 36
•;<y
s.
WHEAT BUST.
Bulletin No. 26. of Purdue University
Agricultural Experiment Station
of Indiana.
GENERAL  NOTES ON FUNGI.
Excepting to scientists who have made
continued study of minute organisms,
and a few persons who haye been specially interested ln the Uterature of these
subjects, the term
fungus (plural fungi) does not convey
a very definite idea Nffip?.
of the myriads of in- yiht
dividual plants in-
oluded by the term.
Neither does it always give a comprehensive idea of the
enormous power
possessed by these
minute objects for
good or for evU.
. While the idea of a
fungus is commonly
connected with some
such visible form as
the mushrooms or
the common moulds
which live upon decaying vegetation,
•these are but the
moat noticeable
ones; the great ma-
j ority are either only
visible in the aggregate or are wholly
microscopic.
Fungi, unlike or-
-dinary plants, are
unable to assimilate
rfood from the simple
compounds, but
must Uve upon organized foods, that
ls,previously formed
plant or animal substances. Some produce decay or live
"Upon already decompose d organ-
.tarns, and are known
as saprophytes .whUe
otbtrs associating
them selves with Uv-
fe
%
£__
ing organisms, live upon the foods con.
structnd by the hosts for their own use
and aro termed parasites. Ot these microscopic -plants the number of species by far
exceeds that of flowering plants, and the
number «1 individuals of the various species as compared with that of common
plants is Inconceivable. Many mnst be
considered enemies to our best interests,
while others are among our best friends;
to draw the Une between these, which to
befriend and whieh to resist and force to
extermination, if possible, ls a most im-
. portant field for study.
In general, it may be Mid that a diseased
'condition of growing crops may arise
•from at least three distinct causes: Un-
't-worable physical and chemical conditions, the depradation of Insects, and
t-throngh the action of saprophytic and
"perauitio plant growths. These latter are
iin no manner to be considered as the least
'of these evils. To this olass of plant diseases belong the "Might" of the pear tree,
potato "rot," "black knot," ofthe plum,
; and the "black rot" of the grape—diseases
which, over great tracts of our country,
have almost exterminated the branohes of
• industry which have borne the force of
-their attacks. Many simUar diseases,
wnoh asthe grape mUdew (Peronospora
•vitkola), are being successfuUy treated;
yet many others from which the evil effects are none the less apparent, such as
the rustUng andsmutting of cereals, seem
to be oonsidered as inevitable and axe al
lowed to continue their effective work
with but sUght resistance upon the part ot
the agriculturist.
Many of onr farm crops are of so extensive and cumulative nature that treatment
of individnal plants becomes practically
impossible, hence a disease suoh as the
rusting of wheat, which does not become
-visible until it is weU at work, is, after lt
has once attaoked a crop, essentially beyond control. Yet that which may not be
cured may often be reduced to Umited
bounds by persistent rational attempts at
prevention.
DESTRUCTIVE CAPABILITIES OP RUST.
There ls, perhaps, among the numerous
diseases of our cereal crops not one that is
or can be of more disastrous consequences
to the farmer than the various species of
rust whioh attacks his field crops. I say
various species, for though, when speaking of rust in regard to farm crops, we
generaUy think of the most apparent one,
this Is doubtless a very low estimate of
the actual loss occasioned to the wheat
fields of Indiana. The State being among
the largest wheat producers of the country, it will be seen that our farmers, even
at this low figure, must stand ln the aggregate an annual loss of from three to
five hundred thousand dollars. The U. S.
census reports the yield of wheat for the
State of Indiana, orop of 1879, to be 47,284,-
853 bushels. The total valua of this crop
at 75 cents per bushel wai therefore $35,-
463,639. Granting that rust damaged this
crop to the extent of 1 per cent, the actual
pecuniary loss to the farmers of the State
through the action of this parasite was
$354,636 39. The average annual wheat
yield of the United States is placed at 512,-
763,500 bushels. Considering the value of
this crop at 80s. per bushel, a loss of the
one hundredth part by rust represents a
total annual loss to the wheat producers
of our country of $4,102,108 figures which
Fio. 2. A pustule of young teleutosporeB of P. coronata Cda. qpou ajj oak leaf, jeep lp cross section-
showing the relative position of the fungal tissues to those of the host plant; a, epidermis; /*>, hypodepmal
leaf cell; c, fungal hypha); d, young spore just previous to the formation of the cross wall which se'parateg
the spores into two cells; e, a mass of f nsed hyph__ in section.   X650.   Original.
Puccinia graminis, which is generally
termed the common wheat rust, yet,when
circumstances are favorable, wheat becomes attaoked by at least three species,
Puccinia graminin, P, coronata and _P.
rubigo-vera. The last two species do not
in their mature form rupture the surface
covering of the plant (Fig. 2), but produce
the spores (teleutospores) under the epidermis and are therefore less easily visible,
yet their development is none the less extensive. AU three of these species are also
common to oats, barley, rye and various
of the grasses. Many grasses are also snb-
j eot to other species peculiar to themselves.
Every farmer has in these nuts dangerous
foes whioh when conditions are favorable,
very materially reduce the yield and value
of the orop.
In the chief wheat producing portion of
England, known as the "fen" oountry,
embracing the comparatively smaU era of
15,000 aores, it is estimated that the loss
from rust alone in the year of 1881
amounted to over $3,000,000; and though
the yield is muoh higher than the average
for this country, yet lt is quite common
for rust to be credited with damage equal
to 50 per cent of the normal crop. The
disease is prevalent to a greater or less
extent ln all parts ofthe United States
and, under present conditions, may be
found in any wheat-field in this latitude
by the 20th of May in quantities great
enongh to menace the surety of a crop; so
that lt may be considered that the fact
that the disease does not often attain to
the disastrous proportions with us that it
does ln some countries is not dne to an
absence of the fungus, but more properly
to atmospheric and soU conditions favorable to a rapid development of the wheat
plant and detrimental to that of the parasite at a time when the damage ls usuaUy
done. However, few farmers would consider that rust usually takes less than one
hundredth part of the wheat crop; and yet
in themselves, are quite astonishing, yet
must be low. Nor to the average farmer
is this all.   The straw when badly rusted
f several
i in the
one of
-y dis-
>t or
• ot
-ier
T
are capal
apparent
course of
which ap*
similar t
spring fo
the dlseaa
Is always')
numerous *»
preceding!
the paras)
and horti^
these form
or weed, wj
out loss to j
gested   ah
structlon ol
possible thi
by furnish!
for the alte
conslderabl,
forms of fni
this paper :
mains in di
cycle.   Muci
way of close]
definite waj
eradication <
disease.
BJ3D RUST ANJ) 3__ApK RUST.
It Is a common expression among wheat
growers that "red" rust does little damage
to wheat, but when the "black" strikes It
the crop is gone. This expression would
seem to embody the thought that the two
were not only diHsrent diseases, but also
different in their mode u- ^cUon upon the
wheat plant, which in tho light of present
microscopical knowledge of their struoture
is wholly erroneous. They are but different stages ln the development of an individual fuDgus. By the unaided eye we
can see only the pustules of rust, the fruit
of the parasite, consisting of aggregations
of very small spores.
Under the microscope the spores of the
two stages appear even more diverse than
do th<* pugtules^ompare fig. 4 and 5; yet
close observation shows that hotli arise
from the same vegetative fungal hypkd,
thread-like filaments which  ramify  the
MffO
(    *1M1JV\.V.|-J'„j/       r •*'
VW&!
A
c-
m
Fio. 3. Cross section of a pustule of rust In the "red" orsnmmer stage of P. rubigo-vera, showing the relation ef the spores to the host tissues and the fnngal hyphe from which they arise; a, epidermal layer o'
cells ruptured and thrown back by developing spores', 6, stomatal opening or breathing pore; c, a portion
of the leaf vein (flbro-vascular bundle) seen in cross section; d, a cell of the mesophyll area containing
chlorophyll bodies not dis organlaed by the action of the fungus; e, fungal hyphic which absorb nourishment from the cells of the wheat plant;/.mature spores which have been pushed off frem their pedicels
by the spores which arise from below.   X 400.   Original.
becomes almost worthless lf not injurious
as a fodder; and in our State, where much
of the crop is housed previous to threshing, the disagreeable amount of dust In
these operations occasioned by the rust, is
not the least of the many evils which combine to lessen the farmer's profit.
NATURE OF WHEAT RUST.
Wheat rust belongs to a division of the
rusts known to botanists as hetercecUmal,
the meaning of which term is essentially
embraced in the thought that these plants
tissnes of the wheat plant; the "blaok"
spores often occupying the old pustules ot
the "red,"only appearing later in point of
time. As the "red" is necessarily the
forerunner of the "black," and furnishes
the spores for the general distribution of
the disease at a time when most damage
ls being done to the crop, it ia the one
most to be guarded against, "black" must
inevitably follow the "red," unless the
crop has been harvested before the fungus
reaches this last fruiting stage.   That the