The Jasper weekly courier. [volume] (Jasper, Ind.) 1858-1922, 1901-03-08
NO. 97


Purdue University Experiment station.
Feb. ~, 1891.
The opinion is quite prevalent
among farmers and many fruit
growers, that the disease known as
Black Knot, 50 often found upon
plum anu cherry trees, is caused by
certain insects. Ii is true that we
may often find upon cutting open
these knots, the larvae of certain in
sects, but it is a universally recog-
nized fact, among those who have
given the matter careful attention,
that these unsightly, knotty excres-
ences are due to special fungus
which is almost always confined to
the plum and sour cherry. The in
sects are there, because they find
these knots to be good breeding
places.
The swellings are first noticed ia
early spring, often as soon as growth
begins. They are then of yellow
ish color, but get darker with age.
In May and June, crop of spores,
which answer to seeds in higher
plants, appears on the surface of the
knots, resembling to the naked eye
soft downy covering. This soon
disappears, when the knots continue
to get darker until winter, when
they have the characteristic black
color, which makes them SO con-
spicuous at this season of the year.
If examined carefully late in the
fall, the surface of the knot will be
found to be covered with great
many minute pimples or elevations,
each one of which is fruit of the
fungus in which the winter spores
are contained. These are in turn
distributed later on, and find lodg-
ling place in the crotches OF limbs
and in the openings Of the bark, and
at the functions Of the annual
growths. As these spores germi-
nate they send their vegetative or
Igans into the growing tissues of the
branch causing swellings, which
often extend along the branches four
or five inches. These vegetative
Tissues do not all die during the win
tier, but some live over and SO hew
swellings, at the edges Of the old
ones, may be seen the following
year. In this way the branch may
continue to be infested until finally
lit becomes completely surrounded,
when the circulation is cut oft and
the branch dies. When these knots
Iappear upon several branches at the
same time, it is only question of a
very short time before the tree will
die.
Treatment.-The treatment gen.
orally recommended is TO cut of the
knots and burn them, which is q
good thing to do, if it is done before
the winter spores have been dis
tributed. If not, then some addi-
tional treatment will be necessary.
1t is recommended therefore, that
all "knots" be cut off and burned
during this month, (February) and
lin addition to this, spray the trees
with a strong solution Of Bordeaux
mixture during the first warm days
Of spring. About the time that buds
start, spray again with the ordinary
g strength Bordeaux mixture. This
ought to destroy all of the winter
spores. Then in case the branches
may have been already infected the
previous year, they should be
sprayed again during the latter part
OF Nav and the first Of June. The
young knots may be destroyed by
= painting them with chloro-naptho-
leum or with pure kerosene oil.
7, Whenever these remedies are thor.
! oughly applied, there will be no
trouble in controlling tbs disease
I, providing all old, worthless trees
: have been cut out and burned and
i provided also that all the people OF
! the entire neighborhood cooperate
elm this plan Of action. Wherever
oIthe Damson plum is grown this dis
ease is almost sure to be present;
, and il is one Of injurious plant dis
I leases" referred to in the Indiana in.
Ispection law. The necessity for
prompt action on the part Of all own
ers Of infested trees, will be evident
4 to all. j. TRooP, Horticultural.