Dwarf Golden Arborvitae Is Dying

Leaf Drop

• When an arborvitae drops leaves, it isn't always because the plant is dying. Like all evergreens, dwarf golden arborvitae sheds foliage in autumn, about the same time deciduous trees turn red or gold before dropping their leaves in preparation for winter. Sometimes the shrub may drop a few leaves in the spring. A normal leaf drop usually involves growth nearest the trunk. If needles drop from the tips or outsides of the plant, look for signs of insects or disease.

Pests

• Arborvitae is commonly bothered by various insects that stunt growth and cause the foliage to wilt or turn brown or yellow. Treat sap-sucking pests such as aphids, scale and spider mites by spraying the plant with insecticidal soap spray, which is less toxic than other insecticides to lady beetles and other beneficial insects that prey on the pests. Spray the plant thoroughly, coating the tops and bottoms of the leaves. Continue to spray every four to seven days because soap spray kills only on contact and has no residual effect.

Disease

• Although a healthy arborvitae is seldom affected, a plant stressed by drought, heat, poor drainage, insects or other problems is susceptible to fungal diseases. Leaf spot is a common disease recognized by small black spots and growth that turns brown or yellow. The disease may affect a limited area or the entire shrub. Fungal diseases are not curable. Fungicides have limited benefits and are usually not recommended. The best recourse is to remove affected areas and keep the area around the plant free of plant matter and debris. Root rot, usually caused by improper watering or poorly drained soil, is a fungal disease that initially causes stunted growth. As the disease advances, the tree displays wilting, lack of new growth and a reddish-brown discoloration on the lower part of the trunk. Root rot is deadly and the only solution is to destroy the plant and start fresh. However, be sure not to plant a new arborvitae in the same soil, as the fungus remains in the soil.

Sunburn

• Arborvitae requires regular moisture during dry weather. During periods of drought, new growth often turns brown and drops from the tree. To prevent this problem, known as sun scorch, keep arborvitae hydrated during the summer. Water every two weeks, providing enough moisture to wet the soil to a depth of about 2 feet. Sunscald is a similar problem that often results during sunny, dry weather in late winter or early spring. To prevent sunscald, mulch the plant generously in late autumn. Water deeply before the first freeze to ensure the roots are well-hydrated going into winter.

Freeze

• Arborvitae is a sturdy plant that tolerates cold temperatures with little problem because the tree gradually acclimates to a drop in temperature as summer turns to fall and winter. However, a sudden cold spell, especially when the drop in temperature follows a period of warm weather, may damage the arborvitae. Young or recently transplanted plants are most susceptible. While you can't control the weather, you can take steps to make the tree more resistant to cold. Stop feeding the plant in late summer because new growth is tender and more susceptible to damage. Water the plant thoroughly in autumn, as freeze damage is less likely in moist soil. A thick layer of mulch such as pine needles or straw may help insulate the roots.