The Hood River glacier. (Hood River, Or.) 1889-1933, 1915-10-28
ENGLISHMAN SUG-
GESTS REMEDIES

uEAOID uEIfIEDlEaO
(Francis f. Blsckwood-West, F. E.
5. +. Y. s., the author OF the following
article. was formerly government ento-
mOlogist of Ceylon, scientific adviser
to the Fruit Commission of Australia,
psthologist for the Society Of Destrue-
tion of Diseases of Crops. Australia I;
chief of the investigation for the ex-
termination of the house fly in Colom-
b0, Ceylon. The article was recently
written for the Oregonian.)
In the United States the annual loss
from direct fungus diseases to plants
averages about $50. 900, 600. The COM
bined effect of the fungus diseases at
lacking the potato diminishes the yield
of this crop more than $36, 900. 900 each
year. The United States government
further reports that the losses from
the cereal rusts and other diseases of
fruit and other crops amount to hun
dreds of millions Of dollars.
Professor W. A. Orton in his great
work says: THAT of still greater i'm
portance is the indirect loss resulting
from the limitations Of industries. The
risk from disease frequently operates
to reduce the production of otherwise
profitable crops and IN many cases in
dustries have been abandoned on this
account"
The following figures will convince
that the the foregoing statements are
in reality more than suppositiOn:
The coffee leaf disease in Ceylon
caused the loss of at least S85, 900, 900.
Bitter rot in apples causes loss Of
$40. 900, 900 annually in the United
States.
Scab in apples causes a loss of $4,-
600, 600 annually in the United States.
Smut in oats. SIS, 900, 900 annually.
Australia in one season experienced
loss of $40, 800, 600 from wheat rust.
Much of this loss could be prevented,
but the individual grower must first
acquaint himself in general way with
the history of the diseases affecting his
crops and so be able to carry out any
proved remedy or check.
The three divisions Of vegetable par
asites which cause disease to plants
are the slime mOlds, the bacteria and
the true fungi, and the term fungi is
used TO include all three divisions.
Now all these divisions are void of the
green coloring matter of leaves (chlo-
rophyD and so differ from the green
plants in the ways which result from
this deficiency. They also have no
ability to elaborate their own foods and
so they are limited to such food as they
can obtian from other plants, and so
they are parasitic. Some fungi live on
dead matter, but although 1t has been
proved that, though sustaining them
selves on the dead parts of living
plant, they cause the other living
tissues to die, but the more important
group to study is the true parasitic
fungus.
There are II different named groups
of parasitic fungi causing diseases. but
it would be useless for me to describe
these groups at present, as the most
important question is the method of i'll
fection.
Plants are infected by means of
spores or cells which are carried by
wind, rain, insects. etc., onto the plant
and the plant is infected, and more of
ten than not dies. Now, it is a we'll
known fact that certain fungi are only
parasitic on certain plants and will not
infect any kind of plant they happen to
light on. For example, we will take
the rust of wheat (puccinia graminis) q.
This disease has attacked wheat
throughout the whole world, but ex-
periments have failed when other host
| plants have been inoculated with the
! oil hotD
ing to the wheat family. which proves
to US that the spores of the fungus are
attracted only to the plant that will
provide the nutriment essential to the
life of the spore. Much trouble and
money can be saved by remembering
this point. for many men seeing a leaf
| spot on one tree or plant and another
leaf spot on another tree will lmmedi-
ately come to the conclusion that the
disaese is spreading and destroy them,
when the two diseases are entirely diff
| ferent species.
The attraction or repulsion exhibited
by certain chemicals to living cells or
spores is called chemotropism and the
substance or food which the spore oh
tains is called a chemOtactic substance.
Now chemOtropism is the force that
enables a parasitic spore to enter, the
plant. All spores have germ tube
which is so highly specialized that they
are attracted to the one special sub.
stance that they are looking for and
from which they can find nutriment,
but on alighting on plant which does
not obtain the proper substance the
germ tube can as easily repulse the
plant as 1t can accept it, although the
highly specialized spores gerimnate on
every kind of plant.
Yet, if the chemotactic substance at
tractlve to the germ tube of the spore
is not present the germ tube of the
fungus does not enter into the tissues
of the plant and so the plant does not
become infected.
Recent Investigations made by emf
nent men have proved that certain
plants Of the species infected by the
fungus have not been infected because
they were without the chemotactic sub
stance that enabled the fungus to in
feet the plant. In other words, the
plant was immune. Marshall Ward
tells US that the capacity for infection
or for resistance to infection is inde-
pendent of the anatomical structure of
the leaf and must depend on some
other internal factor or factors in the
plant. The factor he has proved to be
the presence of chemotactic sub
stance in the plant, to which the germ
tubes OF the parasite respond. The
factor for immunity, if it may be so
put, is the absence of the necessary
chemotactic substance.
The spores of parasitic fungus in
feet the plant chiefly during the night
because the surface of leaves is COW
cred with a film of moisture which is
necessary to enable the spores to