BROWN FOLIAGE ON JUNIPER PLANTS

                        

Phomopsis blight is a fungal disease that affects juniper shrubs, and to a lesser extent, cypress, false cypress and arborvitae plants. This disease infects the foliage and then can move into smaller stems and kill them by creating cankers and girdling the stem. Larger stems can also develop cankers but usually don’t die back.

Plant tissue infected with Phomopsis blight fades to a lighter green before dying and turning a reddish brown color. Drought stressed plants can show similar dieback but the line between live and dead tissue is not as clear as it is with Phomopsis. Other needle blights in junipers usually begin with older needles and work their way up the stem but Phomopsis starts at the tip and works down toward the center of the shrub.

Another disease, Kabatina blight is, to the naked eye, nearly indistinguishable from Phomopsis but is active earlier in the year. Kabatina blight can become active as early as March in Michigan.  Kabatina is infective in the fall of the previous year. Phomopsis is active in late March and April and again in August and September, and the dieback can occur any time during the season. Even short periods of high humidity and temperatures can initiate the development of Phomopsis spores. 

Control of Phomopsis blight involves planting resistant varieties, spacing new plants so they can dry, avoiding shaded areas, watering in the morning so the foliage can dry, and pruning on dry summer days.

Because this shrub disease is hard to diagnose in the field it may be necessary to submit a foliage sample to a laboratory before starting a fungicide program. Phomopsis blight can be reduced with a regimen of proper watering, adequate soil fertility, sanitation pruning, and spraying with fungicides when necessary.