What is the role of zinc in apple production?

Zinc functions in many enzyme systems and biochemical functions including acting as a precursor of indoleacetic acid which is involved in shoot elongation. The micronutrient thus plays a major part in bud development and flowering. Poor zinc supply restricts leaf and bud growth and development, leading to bare bark or rosettes of spindly leaves.

Pre-bloom applications of zinc can help aid the recovery of winter injured trees and also ensure supplies are not limiting during flowering and new fruit formation, as trials with Empire apples in Us show.

Zinc effect at growth stages

Stage	Zinc effect
Bud Burst – Start of Flowering	To optimize bud burst and early leaf development
Post Harvest	Replenish reserves and strengthen new buds

Zinc deficiencies in apples

Symptoms occur in the spring and include chlorosis of the youngest shoot leaves, which are stunted and narrower than normal – ‘little leaf’.

Yellowing occurs between leaf veins and is less symmetrical than, for example manganese deficiency. The leaves may show a wavy margin. Blind bud and rosetting can also occur. Leaf symptoms are not strong in apples compared to other fruit trees.

Extreme deficiency results in shoot defoliation and the production of misshapen and poorly colored apples.