Camellia Diseases & Insects

Camellias have beautiful flowers.

Camellias are evergreen shrubs ideally suited to the U.S. south and Pacific Northwest. They are hardy in USDA zones 7 through 9. The Japanese native Camellia japonica blooms from November through April, grows 10 to 15 feet high and is about half as wide. China's Camellia sasanqua blooms from September through November and is a smaller, more open shrub than its Japanese cousin. Both shrubs have single and double flowers in shades of red, white, pink and bi-colors.

Good Culture

Following good gardening practices with camellias will lessen their chances of becoming diseased or attracting insects. Plant them in moist, well-drained soil that is acidic and highly organic. Feed with a fertilizer especially formulated for acid-loving plants. Site them in partially shaded areas with good air circulation. Clean up any fallen leaves or flowers. Water plants at the root and try to avoid splashing water on the leaves.

Insects

Aphids attack new growth.

Aphids frequently cluster and feed on tender new growth. They also secrete a honeydew substance that promotes the growth of black sooty mold fungus. Light infestations can be removed by hand or with a strong stream of water, but heavier infestations should be treated with horticultural soaps or insecticides.

Spider mites are a particular problem in very humid areas of the south. These sucking pests cluster on the bottom of leaves and create a mottled appearance on the underside of the leaves. Sometimes you will see their bright red egg clusters or a fine spiderweb appearance on the leaves. Light infestations can be washed off, but insecticides might be needed.

Thirty types of scale attack camellias, but the most common is the tea scale. These insects live on the bottom of leaves and in large clusters, and they can look like fuzzy masses. You will see netting or spidering on the top leaf surface. Good pruning practices that open up the plant promotes good air circulation and reduces the likelihood of scale infestation. You can scrape off or hand pick light amounts of scale, but heavy infestations will require insecticides such as acephate, malathion or carbaryl. Clemson University suggests two applications of horticultural oil 10 days apart in the spring when temperatures stay between 40 and 85 degrees F.

Fungal Diseases

Dieback (Glorerella) is a fungus that enters the plant through wounds, so being careful not to bump plants with lawn mowers and trimmers will help prevent this disease. New growth in spring wilts, leaves drop and eventually entire twigs brown and drop off. Sunken spots called cankers will develop on older woody growth. This disease is more severe in very warm and humid weather. Try to minimize overhead watering and increase air flow around plants. Prune infected branches 6 inches below visible damage and clean up all fallen debris. Clemson University suggests dipping pruning shears in a solution of 1 part bleach to 9 parts water in between each cut, then applying the same solution to the pruning cuts.

Exobasidium leaf galls are more common on Camellia sasanqua than on C. japonica. It is usually noticed in the spring when new growth enlarges, thickens and turns fleshy, eventually turning white or pink. Hand pick off infected leaves and destroy them; clean up leaf litter from under the shrub.

Flower blight affects only the flowers and ruins the appearance of the shrub. It is more common in early spring when temperatures are on the rise. It can be confused with cold damage, but cold damage affects most of the buds on the shrub whereas flower blight might affect only a few buds. Also, buds with flower blight develop brown spots and have a netted appearance. The best prevention is good plant hygiene, especially removing and destroying infected buds and keeping the area under the shrub free from leaf and flower litter.

Viruses

Camellias are susceptible to one virus in particular: the camellia yellow mottle virus. This disease causes irregular yellow mottling and splotching on the leaves; entire leaves can turn yellow. There might also be white splotches on flowers. There is no cure. The disease is spread by root grafts and propagation of infected stock plants.

Be an Informed Shopper

Inspect your plants before bringing them home from the nursery.

One of the best ways to prevent insect and disease problems is to not bring them home in the first place. Be a savvy shopper. Always inspect prospective plants carefully for any sign of insects or disease. Be especially diligent about the undersides of leaves, where insects often hide. Plants should be symmetrical and evenly bushy--lopsided plants can be a sign of root problems. Make sure any leaf or flower variegation is integral to plant variety and not the result of a viral infection.

References

• Clemson University: Clemson Extension: Hone and Garden Information Center: Camellia Diseases & Insect Pests
• The Virginia Camellia Society: Education: Disease Problems of Camellias
• University of Florida: IFAS Extension: Camellia

Resources

• American Camellia Society