Informational table showing disease name, symptoms, pathogen/cause, and management of Arborvitae diseases. Disease Symptoms Pathogen/Cause Management Branchlet The oldest branchlets turn brown in autumn and fall off. Normal browning. Branchlets rather than scale leaves are shed in autumn as a normal part of the plant development. Kabatina twig blight Tips of one-year-old branches die and turn brown or ash gray. These remain on the shrub for many months. Larger branches can be invaded and girdled. On the dead tissue where it meets the still-living wood, small, black, pimple-like fungal fruiting structures form. Microscopic examination reveals oval, colorless spores. See Phomopsis below. Kabatina thujae Prune and destroy infected twigs and branches. Both Kabatina and Phomopsis twig blight can occur on the same plant. Apply a fungicide to protect plants. Pestalotiopsis tip blight) Twig tips turn tan to brown in color and have black, pimple-like fungal fruiting structures dotting their surface. Pestalotiopsis funerea Protect plants from winter injury, drought, and other stresses. Apply a fungicide to protect plants. Phomopsis twig blight Tips of branches die and turn brown or ash-gray. These remain on the shrub for many months. Larger branches can be invaded and girdled. On the dead tissue where it meets the still-living wood, small, black, pimple-like fungal fruiting structures form. Microscopic examination reveals both oval and long, thread-like colorless spores. See Kabatina above. Phomopsis juniperovora Prune and destroy infected twigs and branches. Both Kabatina and Phomopsis twig blight can occur on the same plant. Apply a fungicide to protect plants.