Forest Health Protection, Southern Region

Importance. - Phomopsis blight is primarily a problem in nurseries, where entire crops can be lost. Although older trees are affected, the normal result of infection is only appearance. Eastern redcedar, Rocky Mountain cedar, arborvitae, cypress, and Atlantic white-cedar are hosts.

Identifying the Fungus. - The fungus forms small, black fruiting bodies on the needles and stems. These bodies contain small, oval spores.

Identifying the Injury. - Tips of branches are killed and turn brown. Formation of small, black fruiting bodies at the point between living and dead tissue is common.

Biology. - Young needles are infected by airborne and water-splashed spores. The fungus grows into the stem and causes death of the shoot. Fruiting bodies are then formed, which produce spores that infect other plants.

Control. - No economical control is available for forest trees. For nursery seedlings, fungicides are the primary means of control. Removing infected nursery stock, avoiding the movement of infected seedlings, moving the location of the beds, reducing the number of seedlings per square foot, and not using cedar mulch around the beds should also help.