Plant Disease Notes:
Phomopsis Blight of Juniper

homopsis blight, which is caused by the fungus Phomopsis juniperovora, is a common and sometimes damaging disease of juniper, red cedar, Arizona cypress, and related evergreens. Although the greatest loss to this disease occurs in nurseries, damage may also be seen in landscape plantings of some juniper cultivars and red cedar. Among the varieties and cultivars of juniper most susceptible to Phomopsis blight are J. sabina var. tamarisfolia, “Nicks Compact Pfitzer,” “Andorra Compacta,” “Bar Harbor,” and “Blue Rug.” Frequent shearing and heavy fertilization with nitrogen will increase the severity of Phomopsis blight.

Symptoms. In late spring and through the summer, diseased shoot tips, that at first are light green in color, quickly turn yellow and then brown. The browning may spread down the shoot several inches from the tip. Gray cankers, which mark the original infection site, often girdle the smaller shoots causing a shoot dieback. Tiny black fruiting bodies (pycnidia) of the causal fungus may be seen on the gray cankers with a hand lens. Blighting is often seen first on the lower, inside branches. While seedling and container-grown junipers and red cedar may be disfigured or killed by Phomopsis blight, damage on junipers in landscape plantings is unsightly but rarely serious.

Persistence and Transmission. The causal fungus overwinters in cankers on diseased shoots. In late spring, masses of spores ooze from the fruiting bodies during wet, humid weather. Spores are spread to healthy shoots by water splash or on pruning shears. Continuously wet foliage is needed for infection to occur. With favorable temperatures, the longer the foliage is wet, the more severe the symptoms. Soft, young shoots are much more sensitive to attack than mature foliage.

Control. Phomopsis blight is best controlled by using the following strategies:

• Planting resistant cultivars is the most effective practice for controlling Phomopsis blight in landscape plantings on juniper.
• Purchase junipers with good color and no dead shoots.
• Avoid establishing junipers in heavy shade or on poorly drained sites.
• Space the plants far enough apart to allow for air circulation so the foliage dries when establishing new plantings of juniper.
• Irrigate with overhead sprinklers in late morning or early afternoon to ensure that the foliage dries before nightfall.
• Do not handle or prune wet plants.
• Prune out diseased shoots as they appear. Make cuts about 3 inches below the dying shoot, discard the
• Use fungicides. For effective control, a fungicide treatment program should start shortly after shoot growth has begun and before symptoms are seen. In landscape plantings, additional applications should be made about every 14 days until the new growth matures in early to mid-summer. The fungicides labeled for the control of Phomopsis blight are Dithane T/O, Fore 80W, Zyban 79W, 3336 50W, OPH 6672 50W, OPH 6672 4.5F, Heritage 50W, Banner Maxx, Sys Star, Ortho Lawn Disease Control, and Halt 50W. Refer to the product label for information concerning application rates, directions, and precautions before applying any fungicide.

See Extension publication ANR-500-B, Alabama Pest Management Handbook—Volume 2, for current disease control recommendations for landscape ornamentals.