The Hood River glacier. (Hood River, Or.) 1889-1933, 1916-02-10
APPLE SCAB, METH
obs OF FIGHTING IT
Continued from Last Week.

Continued from Last Week.
With the introduction of lime-sul-
phur as fungicide. experiments were
begun throughout the country to test
its usefulness as compared with Bor-
deaux mixture for the prevention of
spple sesb. 1t was a great sstisfac-
tion to find that this new spray mater
ial was really effective for this pur-
pose and that it did not produce on.the
fruit the Objectionable russeting caused
by the other. Lime-sulphur. however.
is not perfect in all respects, for in the
higher strengths it will cause burning
of apple foliage and even in the lower
dilutions, particularly with drenehing,
it may result in injury to folisge, al.
though this is not usually of great i'm
portance. Under certain conditions,
however. the injury may be quite Sc
we're and in addition to scorch on the
leaves there is also ia serious tendency
to cause sunburn on the fruit in hot
weather.
Other fungicides are now being tried
out experimentally over the country
and new combinations of fungicides
as we'll, IN an attempt to find a suit
able spraying program which will give
the desired control of scab and avoid
at the same time the injuries which
have been mentioned. The Oregon
Agricultural College has been making
tests for the past two years under the
direction of Mr.. Winston at the Hood
River branch experiment station and
some interesting facts bearing upon
the problems of scab control have been
brought to light. Some additional in
vestigations have laid bare many Of
the reasons for the lack of success in
scab control and have pointed out the
way to remedy some of the difficulties.
In connection with the work on apple
scab in the Hood River valley it was
found that the period of most abundant
scab infection in 1918 occurred in the
latter part of June. In the following
year, on the other hand, the most SER
ious infection occurred previous to the
time when the flower buds showed
color. Furthermore. during the season
of 1915, however, the most disastrous
infection occurred as result of long
rainy period commencing perhaps two
weeks after the petals began to fall.
Each year there we're great many
growers whose apple crops suffered
badly. but at the same time each year
threre were some whose apples were
practically clean. Investigation showed
that the men who had clean fruit we're
those who had made an application Of
fungicide not long before the critical
period. This is illustrated also in one
locality where during the past season
there was spell of wet weather fav.
orable to scab four or FIVE weeks after
the bloom fell. In an orchard where
the owner gave the usual four applica-
tions there was but per cent Of
scabby fruit. Another grower in the
same district gave three sprayings
with excellent control as far as he
went, but omitted the fourth applica-
tion. After the rainy period referred
to, 10 per cent of his fruit developed
scab spots.
1t is evident, from these examples,
that where there is such variability in
weather conditions through the spring
that in order to be certain of a clean
crop the grower must protect his trees
| by suitable fungicide throughout
the entire season from the time the
buds begin to open until all dt nger OF
scab-favoring weather is past, or else
he must acquire more skill as weather
prophet than most of US ever hope for.
In addition to the poor results which
have come from failure on the part OF
growers to keep their trees protected
during the dangerous period, we mus,
mention the poor results that are at.
tributable to lack of thoroughness.
There are abundant instances in our
appIe-growing sections where two
neighbors using practically the same
spraying schedule will have entirely
different results as far as scab control
is concerned, simply because one has
always done the work thoroughly while
the other has not. Too great emphasis
cannot be laid on thoroughness. Grow.
ers must understand clearly that any
portion of the surface of fruit or leaf
not covered with spray mixture natur.
ally remains unprotected against infec-
tion. A spore can germinate and pen
citrate fruit or foliage at any point
where no fungicide has been deposited.
Wherever destroying or plowing un.
der the fallen leaves has been done
there seems to have resulted marked
diminution in the primary spring infec-
tions. We doubt whether it is possible
to do so through a job. however, that
spring spraying could be safely aban.
doned; but present evidence indicates
that it is desirable practice which
ought to be encouraged. II may per-
haps be possible to destroy the fungus
in the fallen leaves by some spray
applied to them after they have fallen,
but experiments with the standard
fungicides have given negative results.
These. however, form practically in
soluble coating on the exterior of the
leaves and would not be likely to have
any effect on the fungus which in this
stage lies unprotected within the leaf