Copper (Cu)

Copper deficiency is rare in California stone fruit orchards but has been observed in plums growing on Nemaguard rootstock. Symptoms include shoot dieback and formation of small, chlorotic and malformed young leaves. Rough bark accompanied by gumming also occurs. We are not sure of the deficiency threshold, but affected leaves we have tested have been around 3.0 ppm. Commercial peach orchards generally have between 4.0 and 10.0 ppm in mid summer leaf samples (survey). Correction of the deficiency can be accomplished with soil or foliar applied fertilizer materials containing copper.

Nutrition Chapter in UC Stone Fruit Manual

Copper deficiency of plum that can occur when Nemaguard is used as the rootstock