Spanish explorers brought pomegranate trees to the southwestern United States in 1769 and they've thrived in Arizona, California and some parts of Texas since. The shrubs grow 16 to 20 feet high and produce large fruits covered with a rust-colored, leathery skin. The fruit contains hundreds of juicy, acrid-tasting seeds covered by pulp and a soft membrane. Pomegranates are eaten fresh or used for juice or cooking. Diseases and pests are uncommon, but are more likely in humid climates.
The female whitefly lays eggs on the undersides of the leaves. The larva hatch and feed off the sap of the leaves, excreting a thick, sticky substance called honeydew. Sooty mold develops on the honeydew, causing yellowing leaves and stunted growth. Spray the pomegranate tree every eight to 10 days until symptoms subside with Triazophos 40 EC, according to package directions.
Yellowish green aphids also live on the underside of the leaves and cause yellow patches to develop. Hang yellow sticky traps among the developing fruits. Spray the undersides of the leaves with a nozzle hose attachment. Spray dimethoate or malathion according to package directions every 15 days.
Pomegranates may have difficulty obtaining iron, magnesium or zinc from the alkaline soil found throughout Arizona, causing leaves to develop chlorosis, turn yellow and drop. If you see no signs of insect infestation, the problem might be a nutrient deficiency. Iron deficiencies affect the youngest, outer leaves first. Apply iron chlorate fertilizer to the soil as directed. Zinc and magnesium deficiencies affect older, inner leaves first. Apply a balanced, acid fertilizer. Amend the soil with compost or moistened peat moss to lower the pH level.
Pomegranates are drought tolerant and prefer semi-arid conditions, but benefit from a watering every two to four weeks during dry conditions. Trees younger than three years old, especially, need watering and may show signs of drought stress, such as yellow leaves, stunted growth and decreased fruit production.
Pomegranates grow outdoors as far north as Utah and Nevada, but rarely produce fruit. They thrive in dry, warm climates and sustain considerable damage when temperatures dip below 12 degrees Fahrenheit. Cold temperatures may cause yellow leaves or damage to the wood of the tree.