The news & observer. [volume] (Raleigh, N.C.) 1894-current, 1902-11-04
The second paper was read by Cadet
j. c. Beavers. of Wake who treated of:

j. I. beavers. or wake, VINO treated of:
RUSTS ON THE CEREALS.
Rusts are widely distributed over the
world wherever cereals are grown.
The amount of damage done by rusts
can hardly be estimated, but Mr.. Mark
Alfred Carlton, Assistant in the Division
Of Vegetable Physiology and Pathology,
says that the annual grain loss from
rusts in the United States far exceeds
the loss from any other enemy, insect.
or fungus, and often equals those from
other causes combined.
There are several hundred different
kinds of rusts. many of them on weeds
or other unimportant plants, but l shall
describe only one or two of them.
Wheat rust makes it's first appearance
in early summer, causing dark red spots
to form on the leaves, either in the up
per or lower surfaces. These red spots
contain the spores, which are parts espe-
cially organized to reproduce the rust.
Here is a diagram of spore of the
wheat rust, greatly enlarged. You see
that it is round and has a rough sur
face. The wheat rust is really caused by
a very small, lowly organized plant
which grows within the tissues of the
leaf and sends to the surface of the leaf
numerous stalks, as shown in the dia-
gram. Eeach of these stalks bears a its
tip a reddish spore like this. The spore
is to the rust what a seed is TO an ord-
nary plant, i. e., it serves 10 reproduce
the rust. AS these spores occur in great
numbers they form the rusty looking
lines and spots, like these, which give
name to the disease. These spores are so
small that it would take $4,000 placed
end to end to make an inch. These
spores ripen in ten or fifteen days from
the time the injecting spores fall upon
the plant. After these spores ripen they
are loose and are easily carried by the
wind to uninfected plants where they
alight until sufficient moisture is afford
ed for termination. Then the spore
sends out a tube, which enters the it's
sues of the leaf through a small opening,
the breathing pore of the plant, as you
see in this diagram. Here the rust de-
velcps, producing more spore-stalks
which again bear at the tip more spores.
These spores are carried, as before by
the wind to new hosts. Thus you see
rapidly the disease spreads.
1t was once thought that this complet-
ed the life cycle of the rust, but more
recently it has been found that this is
only one stage a stage now called the
summer stage" and the spores the
summer spores" Toward the end OF
summer this same rust develops spore-
stalks, which bear entirely different
spores from the Mound thin walled spore.
These spores are like these shown in this
diagram two-celled with a thick heavy
wall around them. This is called the
Black Rust or winter spore, and appears
on the wheat stubble after the wheat is
harvested and of course does the farmer
no present damage. These black spores
are the ''resting Spores" which lie over
winter and are scattered by the wind.
Many of them are carried to the bar
berry leaves in spring. They there ger
inmate and enter the tissues of the
leaves, developing a mycelium, which
produces spores, not as before, but in
cup on the under surface of the leaf as
shown in this diagram. These spores
ripen and are carried by the wind to the
growing wheat, where the disease again
becomes parasitic on the wheat, causing
much damage to the farmer. 1t woulc
be we'll to mention one fact here, namely
that any one of these stages can be
omitted by the rust. The stage on the
barberry is often omitted and the winter
spores are carried directly from the
wheat stubble to the growing wheat il
the spring.
1t is impossible for any kind of rus.
to make appearance on wheat or an!
other plant in any kind of weather un
less the spores of the rust are present
The disease is not caused by wet wealth
er, as many farmers think, but more Of
ten appears in wet weather because the
presence of moisture is necessary for the
termination of the spores. / have eX-
amined the spores of several rusts under
microscope and found those of corn rus
to be like those shown in this diagram
| also planted some of these spores il
water to see if they would terminate
took some spores from growing and put
them on some young corn plants in the
hot house and covered them with wet
piece of cotton. Here are the results
obtained | have here a plant of corn
which has several spots of rust spores
on it. If you We're to examine these