White Bluffs spokesman. [volume] (White Bluffs, Wash.) 1907-1938, 1935-03-28
Variety Is Factor In Frost Damage
CONTINUED from page u


full bloom they are slightly more frost
resistant.
S. Amount of Previous Frost Dam
age-The first damaging frost usually
kills the weaker buds, and sometimes
leaves buds which are able to with
stand even more severe frost on a
later date.
Duration Influences Kill
6. Severity of the Frost-Other con-
ditions being the same, the lower the
minimum temperature and the longer
the duration of damagingly low tenn
peratures, the greater the kill by frost.
It is the duration Of critically low
temperatures that is highly important.
Often a moderate frost of long dura-
ton will secure a greater kill than a
more severe frost of short duration
]. Conditions of Atmospheric Mois-
ture-With apples, greater damage al
most always occurs in the stages up to
and including full bloom when the air
is dry. After the full bloom stage great
err damage seems to occur under moist
conditions. With pears, however, a
coating of ice on the bud or blossom is
more conducive to frost marking and
damage will take place at higher
temperature on a damp than on dry
night.
Smudge Not An Aid
8. Rate of rise in temperature fol-
lowing frost--When plant tissue is
frozen, rapid thawing releases moisture
faster than it can be reabsorbed by
the tissue. The plant cells are ruptured,
dry out, and are killed. When the
thawing is gradual the plant tissue
may be able to take up the moisture
as fast as it is released by thawing. The
plant cells then remain intact and
alive. When blossoms are frozen the
damage may be great or small, de-
pending on the rate at which thaWing
is accomplished. These facts have led
many growers to believe that dense
smudge spread over the orchard just
before sunrise will enable frozen BIOS
SONS to thaw out slowly with less frost
damage than otherwise would be ex-
perienced. AS matter of fact, careful
tests have shown the inefectiveneSs of
this method of frost protection, since
the thawing of the blossoms must be
regulated with almost scientific exact
ness and it is very difficult to secure
the proper conditions with these crude
methods. Following a severe frost the
buds in most cases are by the time OF
sunrise shocked beyond recovery.
Apple trees, like most deciduous fruit
trees, produce a large amount of bloom
that never natures, even under the
most favorable conditions. Assuming a
moderate to heavy bloom, if one fruit
bud in one cluster of four be allowed
to mature-the generally accepted rule
for artificial thinning of apples in such
cases-a practical estimate may be
reached as to the amount of overpro-
duction of bloom. If each cluster con-
tains five buds, the usual average for
most varieties, then if one bud in 20
be allowed to reach maturity to pro-
duce full crop, the overproductior
of bloom is 95 per cent.
In this theoretical case it is obvious
that rs per cent of the clusters arr
not allowed to produce mature fruit
Only Per Cent Set
Practically interpreted, this mean:
that 95 per cent of all the individual
fruit buds, which also includes Is pei
cent of the clusters, can be pinchee
off without reducing the final crop
provided, however, that the remaining
fruit buds and clusters are properly
spaced on the tree and that all bud
produce mature fruit. Moderate bios
som damage can occur without serious
reduction in the final crop since il
such cases usually one or more llv'
buds remain in each cluster, unles
previous frosts have already produced
heavy blossom damage. Small cluste
damage, however, usually means crol
damage to some extent, since alnlos
invariably after damage frost-kille'
clusters predominant in certain por
lions of the tree, usually on the lowe
limbs or along certain sections Of in
dividual branches. A fruit cluster
damaged when all the buds that com
prise. it have been killed, since, at most
each cluster is only allowed to pro
duce one fruit.
It is only by considering blossom
damage in connection with cluste
damage and with due regard to tn
amount Of damage previously done tina
the extent of crop injury may be cor
rectly judged.
Temperatures that will be endure
for 30 minutes or less by deciduou
fruits in various stages of developmer
are given in Table /:
Table Temperature endured fe
80 minutes or less by deciduous fruit
(sheltered thermometers
Fruit Degrees Fahrenhe
2 3
90