Severe copper deficiency: Identified in southern California grapefruit

Symptoms of severe copper deficiency were visually diagnosed in a 27-acre grapefruit orchard near Hemet, California, in February 1958, and again in a nearby orchard in 1962. Typical symptoms were dieback of young twigs, chlorosis of terminal leaves, and misshapen, rough fruit with brown necrotic spots on the outside and gum pockets in the albedo or white portion of the rind. Leaf samples from the orchard contained less than 0.75 ppm copper on a dry-weight basis, thus confirming copper deficiency. The annual application of a copper spray has corrected the severe symptoms of copper deficiency. A minor element study of southern California citrus orchards suggests that approximately 20 per cent of the orchards may possibly respond to a copper spray program.