Polk County observer. (Monmouth, Polk County, Or.) 1888-1927, 1915-08-06
.PRUNE TREES AFFECTED
PARASITIC FUNGUS DAMAGING
In SOME SECTIONS.
Experts Hold That Spraying Is Nee
essary and Give Best Mixture
for Purpose.

AS the prune trees in many districts
appear to be affected by the same dis
ease found on cherry trees early this
summer and as the treatment is prac-
titally the same, the following extract
from circular letter issued by the
experiment station of the o. A. C.
will be of special interest.
THE disease Is caused by para :
site fungus known as cylindrospori-
um This fungus lives over the win
ter in the diseased leaves that have
fallen to the ground. In the early
spring minute spores are produced by
the fungus and are shot by the dead
leaves into the air. They are carried
to the young foliage and cause the
primary infection. Spots develop on
the leaves and in a short time, new
spores are produced. These cause
secondary infections, which become
exceedingly numerous, especially if
there happens to be long continued
wet spell of weather.
The infections result in the pres
ence of small dark spots or specks on
the surface of the leaves. These may
be few, or they may cover the entire
surface of the leaves. On the under
light colored specks, each consisting
of mass of spores, by which the
disease is disseminated. Where the
attack is severe. the leaves turn yell
low. The most serious effect, is in the
dropping of the infected leaves.
Where many leaves are cast, the tree
suffers serious setback, and the
chances for a good crop the next sea-
son are lessened. The fungus will al
SO attack the fruit.
First, the disease must be controll-
ed by spraying with Bordeaux mix
ture. No experiments have been car
ried on in Oregon, but in the eastern
part of the country where the disease
is both common and serious the use
of this spray has resulted in the con-
troll of the difficulty. We therefore,
recommend its use to Oregon growers.
The foliage should be thoroughly
covered, for imperfect results follow
imperfect spraying. A film of the
Bordeaux mixture kills the spores
that fall on the leaf surface and thus
prevents infection. Where the sur
face is not completely covered, spores
may cause infection on the bare spots.
In order to check the disease from
the first, Bordeaux (4-4-50) should be
applied as early as possible, and con-
tinued every two weeks until dry |
weather comes on, so that the newly |
developing foliage may be kept pro-
-ected during the season when the
rains favor the disease. 1t is not pos
;ible to cure the disease of leaves al
'eady infected, but it is possible to
prevent any more leaves from becom-
ng infected, If properly sprayed. Dur
ng the ordinary dry weather of an
oregon summer, there is little danger
If new infections taking place.
Second, 1t has been suggested by a
ecent, investigator of this disease
hat the removal of fallen leaves from
he orchards and from the fence rows
n the fall would be beneficial, since
t is from these leaves that the dis
ase is carried over winter and from ,
hem that the first infections in the
pring come"
While the above was written for ,
he early infected cherry trees, the
Iisease now found on prune trees is ,
declared to be exactly the same, and
hose who have studied plant diseases, ,
gree that the same treatment will s
rove beneficial, and finally destroy
he spores. ,