Calcium Related Disorders

The quickest and most effective short-term corrective
treatments for control of bitter pit and cork in apple are:

Bitter Pit Control. Spray trees with a solution of
either calcium chloride or calcium nitrate. Use 2 pounds
of calcium chloride or 4.25 pounds of calcium nitrate per
100 gallons of water plus a wetting agent. Calcium nitrate
should not be used on trees that contain high to excessive
amounts of nitrogen in the leaf tissue as measured by leaf
analysis or that are making excessive shoot growth. Make
applications at 2-week intervals with the last spray 2
weeks before harvest. These calcium sprays can reduce
bitter pit in apples by 50 to 90 percent.

Cork Control in Apple Flesh. Spray trees with 1.5
pounds of calcium chloride or 3.2 pounds of calcium
nitrate per 100 gallons of water with first cover spray and
include in each subsequent cover spray until a total of 18
to 24 pounds per acre has been applied. The calcium
nitrate sprays will apply 2 to 3 pounds of actual nitrogen
(N) per acre and should be used only on trees that do not
contain high to excessive nitrogen levels as measured by
leaf analysis or reflected in excessive shoot growth.

Dip before Storage. Calcium chloride can be
included in the scald dip. One combination that has been
used successfully contains 50 pounds of calcium chloride
(food grade) in 500 gallons of water plus DPA. Calcium
in the dip provides protection against bitter pit
developing in storage and generally improves the
condition of the fruit in storage. (See the "Scald" section
of Postharvest Diseases under Diseases of Apples.)

Foliar Nutrient Sprays on Apple

For foliar applications use dilute sprays - 1X for
maximum effect.

Notes on Foliar Nutrition
Dr. Ed Stover, of the Cornell Hudson Valley Lab,
conducted two years of research on Nitrogen, Boron and
Zinc as prebloom sprays on apple. He concluded
prebloom nutrient treatments enhance cropping by
increasing retention of flower buds that would otherwise
abscise during early bud development.
The most obvious use of these treatments (N, B, Z)
would be on apple blocks where cropping is expected to
be light. There is potential to increase fruit size as along
as aggressive thinning practices are followed.

Urea (N). Urea is beneficial on apples for helping to

improve fruit set and increase size on apple cultivars that
are low in nitrogen as indicated by leaf tissue analysis.
Use 2-3 pounds of urea per 100 gallons of water at pink
bud, full bloom, and/or at petal fall to improve fruit set
and tree vigor. Use 5 pounds per 100 gallons in covert
sprays after petal fall only on nitrogen-deficient trees.
Foliar nitrogen is not a replacement for ground applied
nitrogen, rather an aid to fruit set and fruit sizing.

Boron (B). Solubor sprays of 1 pound in 100
gallons of water applied at full bloom and at 1 week after
full bloom may reduce cork in apple flesh if boron is
deficient. Boron aids calcium movement into fruit.
Adequate boron is essential; excessive boron hastens
apple maturity and increases fruit drop. Both soil and leaf
analyses are essential in determining the need for boron.
Apply no more than two sprays per season.
Note:Boron may be added to pesticide sprays. Do not
premix Solubor with calcium chloride. Do not apply
boron with oil or apply boron when trees are wet with oil
as an increased uptake of boron may result causing boron
toxicity.

Zinc (Z). Use EBDC fungicides containing zinc.
If Zinc level is low (as indicated by leaf tissue
sample) apply zinc chelate (EDTA) at 1 qt liquid
formulation per 100 gallons dilute equivalent at tight
cluster to pink, repeat 2-3 weeks after petal fall and again
4-5 weeks later
Another application can be made after harvest. Apply
3.2 lbs. actual zinc, as zinc sulfate, per acre. Apply as
foliar sprays, but while the leaves are still green and
active.
Soil applications can also be used to correct long
term deficiencies, especially if soil tests low in zinc.
Broadcast soil applications of ZN at 6.4-12.8 lbs. per acre
of actual zinc.

Calcium.Soil and plant tissue analyses show that a
high percentage of apple orchards in New Jersey are below
the desired ranges for good quality fruit production. These
low calcium levels are associated with bitter pit and cork
in the apple fruit, which reduces its quality and sale value.
Long-term correctivetreatment recommendations
suggested for reducing or control of these nutritional
disorders:
[!]Lime soils with calcitic limestone prior to
planting new orchards, and top-dress existing
orchards to maintain a soil pH of 6.
[!]Apply agricultural gypsum to soils that show
deficient soil and leaf tissue levels of calcium
when the soil pH is at the desired level. Use
1,000 to2,000 pounds per acre before
establishing new plantings, and 1 to 2 pounds
of gypsum per year of tree age, spread under the
drip area of established trees, preferably during
the fall months.
For additional calcium information, see Soil
Preparation

72

1998 New Jersey Commercial Tree Fruit Production Guide