Nutrient Management - Growing Organic Orchard Fruits - page 375

Magnesium (Mg) Deficiency
Symptoms. Yellowish-brown necrotic areas appear, generally first
between the veins on older leaves. Spurs and new shoots may be thin,
weak, and brittle. Fruiting spurs may fail to develop (blind wood).
Leaves and fruits may drop prematurely.
Treatment. Apply 500 lb/A (18 oz/100 square feet) of magnesium
sulfate (Epsom salts) or potassium magnesium sulfate (sul-po-mag)
when symptoms develop or in early spring. Apply to the soil, not to the
foliage.
Boron (B) Deficiency
Symptoms. The most characteristic of B deficiency symptoms include
delayed bud break, poor flower development, and poor fruit set. Shoot
terminals and spurs may abort, and leaves are often small, narrow,
and elongated. Apple fruits may develop corky spots within the flesh
and wrinkled skins.
Treatment. Apply a soluble boron-containing product as a foliar spray
during the growing season or to the soil in early spring. CAUTION —
boron becomes toxic to plants at very low concentrations. Never band
boron fertilizers within crop rows. Use soil and foliar tests to determ-
ine the need for boron. Do not apply more than 1-2 pounds of actual
boron per acre. Follow label directions when applying foliar spray ma-
terials.