The addition of foliar nutrients has become standard practice for most progressive apple growers to help
set fruit and prevent certain physiological disorders. Research by Dr. Ed Stover, formally of the Cornell
Hudson Valley Lab, conducted two years of research on Nitrogen, Boron and Zinc as pre bloom sprays
on apple. He concluded pre bloom nutrient treatments enhance cropping by increasing retention of
flower buds that would otherwise abscise during early bud development. He indicated "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 cover sprays after petal fall onlyon nitrogen-deficient trees. Foliar nitrogen is not a
replacement for ground applied nitrogen as it does not translocate down into the wood, rather its 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
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) -- Tight Cluster to Pink --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. Low levels of Zinc are know to cause small fruit size
especially in Red Delicious, even when no other symptoms of zinc deficiency are evident. Most of our
New Jersey soils and orchards are deficient in Zinc.
Calcium (Ca)- The quickest and most effective short-term corrective treatments for control of bitter pit
and cork in apple are for Bitter Pitcontrol, 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.
To controlCorkin 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.
For Calcium sensitive varieties such as Enterprise, Breaburn, Fuji, York, and Cortland apply:
Calcium Chloride (CaCl
2-3 lb/100 prior to August 12):
3-5 lb/100 after August 1