Morris tribune., 1911-11-17
APPLE RUST.
NORTHW EST
BY E. c. Stakman, Minnesota
University Farm.

i. i. i 4" + = ' = = y II 't' = i +" r' #
The rust of apples is very prevalent
this year, and, in some localities,
quite destructive. The Wealthy is
particularly susceptible, so it is de-
sirable to prevent the occurrence OF
the rust if possible.
All fruit growers are no doubt ia
miliar with the appearance Of the rust.
1t appears first as greenish yellow
spots on the upper surfaces of the
leaves. These spots become darker,
eventually assuming an orange hue.
Small, pale yellowish dots appear vers
early in these spots; later the doys
become black Two or three weeks
after the first appearance of the spots
on the upper surfaces of the leaves,
they begin to appear On the lower
surfaces also. Here many small GU
pules with fringed edges are formed.
The disease is caused by fungOus
parasite. The fungus-a very low
form of plant life-lives in the form of
very minute threads in the tissues Of
the apple leaf, or, more rarely, in the
fruit or young twigs, 1t does not
make it's own food, but absorbs il
from the tissues in which it is grow
ing. thus lessening the vitality of the
entire tree. Reproduction is brought
about by means of spores-extremely
small bodies corresponding roughly
with the seeds of higher plants. At
least two kinds of spores are pro-
duced; and these are produced on diff
ferent kinds of plants. During the
summer, cluster cup spores are pro-
duced in the cupules which have been
mentioned as occurring on the under
surfaces of the apple leaves. They
may also be found on other plants
which are attacked by the same fun
gus; among these are the thornapple
and Juneberry. These spores are
blown about by the wind, and those
which fall on the red cedar may cause
an infection which results in the
formation of the so called cedar ap,
pies. The fungus spends the winter
in this form On the red cedar. In the
spring, during wet weather, the cedar
apples send out gelatinous, hornlike
processes, each of which contains
great many of the winter spores Of
the fungus. These spores germinate,
producing small secondary spores,
which are easily blown about by: the
wind, and, falling On apple leaves,
again cause an infection.
In controlling the rust, the red
cedars must be taken into account,
1t is not known just how far spores
will be blown, although in some
cases they may be carried couple of
miles. Usually however, they are
blown much shorter distances. 1t is
essential that all of the cedar apple
gals be removed in some way. If this
is done, there should be little rust
next year. In the spring, especially
following wet weather, another in
spection should be made The gals
can be easily recognized at this time
on account of the jellylike projections.
These should not be allowed to dry,
since the spores are scattered after
the gelatinous processes dry. The
surer method would be the removal of
the cedar trees, but this is sometimes
undesirable. It should, however, be
done if the cutting out of the gals
proves ineffective. Spraying alone,
although of great value, does not en-
tirely prevent the rust, so neighbor5
should cooperate as much as possible
in removing the cedar gals, and
when necessary, the red cedar trees
themselves