Copper is a micronutrient of plants. In certain situations, soil levels may be low enough or plant growth demand high enough that deficiency may occur. Within pistachio, this deficiency often occurs in the middle of the season (July-August) on young, fast growing trees. Symptoms include the die-back of new growth, forming a “shepherd’s crook.” Most, if not all, new growth will show this deficiency. In these cases, a foliar spray containing copper can help remediate the deficiency. Ideally, deficiency should be prevented to maximize growth. To prevent copper deficiency, plan to apply 0.1 lb/acre or 0.100 kg/ha of a chelated copper as a foliar spray when the new canopy is 50-90% expanded. This spring-time application will prevent the symptoms from occurring later in the summer. Soil applications should also be considered if soil values are low. Cooper sulfate can be fertigated in acidic soils, while a chelated product (EDDHA, or similar) should be used in alkaline soils. Soil applied rates of 1-2 lbs/acre or 1-2 kg/ha should be sufficient.