Cupressus Arizonica Diseases

Juniper Tip Blight

• Although called Juniper tip blight, this condition affects several other kinds of evergreens as well, including cypresses and arborvitae. Rarely fatal, juniper tip blight is caused by Phomopsis and Kabatina fungi. New growth turns red, yellow or brown, then dies. Prune off and destroy infected branches; never add them to your compost pile. Protect your Arizona cypresses by planting them where they'll have good air circulation and by mulching around the base so you're less likely to wound the bark when you mow or trim weeds. Water plants in the morning so the foliage dries completely before evening and don't overfertilize. If other plants in your landscape contract Juniper tip blight, spray your Arizona cypresses with an approved fungicide as a precaution.

Canker

• Caused by the fungus Seiridium unicorne, Seiridium cankers are flattened, elongated wounds on the main branches and stems of Arizona cypresses. Patches of oozing resin are common. The cankers enlarge until they girdle the stem, causing the whole branch to die. In serious cases, the entire tree dies. Prune out infected branches and destroy them; never add them to your compost pile. Also disinfect your pruners between cuts with alcohol or a solution of one part household bleach in nine parts water. Seridium canker also affects arborvitae, Italian and Leyland cypresses and junipers, so if the disease is found, inspect those plants in your landscape as well for signs of disease.

Root Rot

• Cypresses grown in poorly drained soil may develop root rot, a lethal disease caused by a number of different fungi. Symptoms include yellowing foliage, branch and twig dieback, and loss of vigor. A fungicide drench and transplanting to a better location may save minimally damaged plants, but badly infected trees should be dug up and destroyed. Prevent root rot by planting Arizona cypresses in well-drained soil; never plant them in low-lying areas that remain wet or near downspouts.

Good Cultural Practices

• Well-grown plants are less susceptible to disease problems, so careful attention to your Arizona cypresses will reward you with plants less likely to develop problems. Grow C. arizonica in full sun in well-drained soil. The foliage will become thin and sparse in shade, and the plant will languish. This plant is not particular about soil pH or structure, although it develops a better root system in loose soil, allowing it to withstand high winds better than when grown in heavy clay. Once established, Arizona cypresses are drought-tolerant and need supplemental watering only during extended dry spells. When you do water, use a hose, not a sprinkler, and direct the water at the root zone to discourage blight. Arizona cypresses are hardy in U.S. Department of Agriculture plant zones 7 through 9, although some cultivars, such as Blue Pyramid, are more cold-hardy.