Camellia Diseases & Insect Pests

Prepared by Nancy Doubrava, HGIC Horticulture Specialist, and J. McLeod Scott, HGIC Horticulture Extension Agent; James H. Blake, Extension Plant Pathologist; and Clyde S. Gorsuch, Extension Entomologist, Clemson University. Revised by Joey Williamson, HGIC Horticulture Extension Agent, Clemson University. (New 05/99. Revised 12/06. Images added 01/10.)

HGIC 2053

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Camellias are one of the most desirable and well-adapted plants for Southern gardens. Many of the common problems of sasanqua camellia (Camellia sasanqua, C. hiemalis, and C vernalis.) and the common Japanese camellia (Camellia japonica) can be prevented or minimized by following the proper cultural recommendations.

The three most serious camellia diseases in South Carolina are camellia dieback and canker, flower blight and root rot. The most important insect pest to watch for is tea scale. More information on successfully growing camellias is available in HGIC 1062, Camellia.

Diseases

Camellia Dieback & Canker: This is one of the most serious of all camellia diseases and is caused by the fungus Glomerella cingulata. Leaves on affected branches suddenly turn yellow and wilt. Branch tips usually die. Gray blotches appear on the bark and stem, and then sunken areas (cankers) develop, eventually girdling the stem. Parts of the plant above the stem canker lose vigor, wilt and die. Damaged plants show more symptoms during hot, dry weather.

Prevention & Treatment: Keep camellias as healthy as possible. Plant in a well-drained acidic soil, avoid wounding and fertilize properly. Remove diseased twigs by pruning several inches below the cankered areas. Disinfect pruning tools between all cuts, using a solution of one part household bleach to nine parts water. Fungicides, such as thiophanate-methyl (Ferti-lome Halt Fungicide, Green Light Systemic Fungicide, Cleary's 3336) and copper salts of fatty acids (Camelot Fungicide/ Bactericide or Concern Copper Soap Fungicide) can be applied during wet periods and normal leaf drop periods to protect fresh leaf scars from infection. Apply all chemicals according to directions on the label.

Camellia Flower Blight: This serious disease of camellia causes the flowers to turn brown. Flower blight appears in early spring when moisture is present and is caused by the fungus Ciborinia camelliae. Symptoms begin as small, brown, irregular-shaped spots on the flower petals. These spots quickly enlarge to cover most of the flower. The entire flower turns brown and usually drops within 24 to 48 hours. Only the flowers of the plant are affected.

Camellia flower blight turns flowers brown rapidly.
Clemson University - USDA Cooperative Extension Slide Series, Bugwood.org

This disease can be confused with several other problems that can damage camellia flower petals. Slight browning at the edges of the flower petals may be caused by sun or wind. Suspect a disease problem if the brown area rapidly spreads to the center of the flower. Cold temperatures can also cause browning of the flowers. Dark, brown veins in the petals distinguish flower blight from cold injury.

Prevention & Treatment: Sanitation is the best control. Pull off and destroy all infected flowers. Rake up and remove all leaves, flowers and plant debris that have fallen to the ground. Replace the mulch under the plant. This fungus survives in the soil. Spores of the fungus can be wind-borne for up to a mile. Therefore, control is best achieved when controls are applied to other camellia plants in the community.

Application of soil drenches, such as PCNB (Southern Ag Terraclor Fungicide 75W), around the plant in late December or early January is often helpful in reducing the intensity of disease. Fungicide sprays recommended for the flowers include mancozeb (Bonide Mancozeb Flowable or Southern Ag Dithane M-45) and triadimefon (Green Light Fung-Away). Apply all chemicals according to directions on the label.

Root Rot: This fungal disease is caused by Phytophthora cinnamomi. The first symptoms are a uniform leaf yellowing, poor growth and wilting of the entire plant. Infected root systems lack small feeder roots and appear discolored. Infected roots are a red-brown to dark-brown color (healthy roots are white). Death of the plant can occur rapidly, or the plant may remain in a state of decline for several years. All varieties of common Japanese camellia are susceptible and all varieties of sasanqua camellia are resistant to this root rot.

Prevention & Treatment: This disease is difficult to control once plants are infected, so prevention is very important. In areas where this disease has been a problem, select Camellia sasanqua cultivars for planting or request C. japonica cultivars grafted onto a sasanqua rootstock. Purchase healthy plants that show no signs of wilting or yellowing of the leaves.

The fungus thrives in areas with poor drainage and warm soils. Always choose locations that have good drainage for planting. The drainage of existing areas can be improved by using raised beds. Fungicides can be effective on a preventative basis only, and repeat applications are required. Fungicides containing etridiazole (Banrot 8G or Truban 5G) and mefenoxam (Subdue GR) can be applied in the home landscape, but will not cure an infected plant. Due to product cost and for accurate application, homeowners may want to hire a licensed landscaper to apply products containing these fungicides. Apply all chemicals according to directions on the label.

Leaf Gall: This disease is more common on sasanqua varieties of camellia (Camellia sasanqua) than on Camellia japonica. It is caused by the fungus Exobasidium camelliae. Leaf galls are most often observed during the spring flush of growth. New shoots and leaves become enlarged, thickened and fleshy, and appear abnormal. The color of the affected areas turns from light green to nearly white or pink. The galls later rupture on the undersides of the leaves revealing a whitish mass of spores. The galls eventually harden and become brown. Plants are seldom severely damaged.

Camellia leaves affected by camellia leaf gall.
Clemson University - USDA Cooperative Extension Slide Series, Bugwood.org

Prevention & Treatment: Remove and destroy young galls before the lower leaf surfaces turn white and spores are released, or the disease will be worse the next year. Rake up and remove fallen leaves. Avoid wetting the leaves when watering. Humid, moist, shady conditions favor gall formation. Chemical controls, such as mancozeb (Bonide Mancozeb Flowable, Southern Ag Dithane M-45) are limited in effectiveness and must be applied before infection occurs. Start sprays at budbreak and continue through the first of June at 7- to 14-day intervals. Apply all chemicals according to directions on the label.

Viruses: Camellia yellow mottle virus is transmitted by root grafts and propagation of diseased stock. This virus causes irregular, yellow, mottled or splotchy patterns of various sizes and shapes on the leaves. Some leaves may turn entirely yellow. Irregular white blotches will appear on infected flowers.

Camellia yellow mottle virus symptoms
Joey Williamson, ©2009 HGIC, Clemson Extension

Prevention & Treatment: There is no chemical that will cure the virus. Plant only virus-free plants obtained from a reputable garden center.

Insect Pests

Scales: In South Carolina, the most common insect pests of camellia are scales. Scale insects feed on plants by piercing plant tissue and sucking sap. Scales do not look like typical insects. They are small, immobile and have no visible legs. They vary in appearance depending on species and sex. Some look like small fish scales attached to the plant. As a result of their unusual appearance, populations can reach damaging levels before they are noticed.

Tea scale damage to top of camellia leaf.
Clemson University - USDA Cooperative Extension Slide Series, Bugwood.org

On camellia, scales usually attach to leaves but some species also attach to stems. Their feeding weakens the plant. With a heavy infestation, symptoms include yellowing of the upper leaf surface, fewer and smaller blossoms, leaf drop, twig dieback and sometimes death.

Tea scale is the most serious scale insect on camellia. It attaches to the underside of leaves. Tea scale has an oblong shape with a ridge down the center parallel to the sides. It is a small scale with the female about 1/20 inch. The male is about two-thirds the size of the female. The females vary in color from dark brown or gray to nearly black. Males are white. The female lays 10 to 16 eggs, which remain protected under her body until they hatch. In one to three weeks, bright yellow immature forms called crawlers hatch from the eggs. A typical symptom of tea scale infestation is yellow splotches on the upper surface of leaves. With a large infestation, the undersides of the leaves are covered by a cottony mass.

Adult tea scales on underside of camellia leaf.
Clemson University - USDA Cooperative Extension Slide Series, Bugwood.org

Controls: With a light infestation, scales can be scraped off the plant and discarded. If only a few leaves are infested, hand picking and destruction of infested leaves is very effective. The best time to spray with a refined horticultural oil (Bonide All Season Spray Oil, Ferti-lome Scalecide, Green Light Horticultural Oil Spray, or Ortho Volck Oil Spray) is in spring, after the plants have finished blooming and the danger of cold weather has passed. This will kill many adults, crawlers and eggs by smothering them. Spray two applications, 10 days apart. Spray when temperature are between 40 and 85 degrees.

Most insecticides are effective only against the crawlers. In addition, using an insecticide against scales can result in the deaths of naturally occurring enemies of scales. As such, insecticides should be avoided unless the camellia is very valuable.

Monitor the crawler emergence with sticky cards, tape wrapped around a branch, or by putting an infested shoot or leaf into a baggie and watching for crawler movement. Crawler activity often coincides with the flush of new plant growth in the spring. However, some scale species may have overlapping generations with an extended crawler emergence period, such as along the coast.

Insecticides labeled for homeowner use against tea scale crawlers include acephate (Ortho Japanese Beetle Killer), malathion (Ferti-lome Mal-A-Cide, or Hi-Yield Malathion Insect Spray), cyfluthrin (Bayer Advanced Garden Power Force Multi-Insect Killer), and carbaryl (Sevin 50WP or Ferti-lome Carbaryl Spray). As with all pesticides, read and follow all label instructions and precautions.

Other Problems

Bud Drop: Camellia flower buds may drop off of the plant before opening or the tips of the young buds turn brown.

Prevention & Treatment: Bud drop can be caused by several different factors. One of the most common causes is large fluctuations in temperature or moisture. Camellias perform best planted in areas with uniform moisture that are not too wet or too dry. Freezing temperatures can cause buds to drop before opening. Hot weather during the fall or spring may encourage shoot growth and cause the plant to drop its flower buds. Avoid planting varieties that bloom late in the spring and plant in a shadier, cooler location to help prevent this problem. Other plant stresses due to a lack of nutrients, poor soils or drainage can cause flower buds to drop. Camellia bud mites cause buds to develop slowly and either open late or fall off before opening. Camellias that drop their buds year after year may have a varietal problem or a problem of location that can be solved by transplanting.

Sunscald: Camellias planted in full sun or against a south- or west-facing wall often get sunscald. Leaves will develop scorched or bronzed areas on the side of the plant directly exposed to the sun. Leaf-spotting fungi may infect the damaged leaves. Sunscald is a particular problem on camellias transplanted from shaded to sunny locations.

Prevention & Treatment:Prevent sunscald by planting in a shadier location or providing more shade to their present location. Once the leaves have turned brown, they will not recover.

Oedema: This disorder appears as numerous small bumps on the lower side of leaves or on stems. The "bumps" are tiny clusters of cells that divide, expand and break out of the normal leaf surface. At first, they form tiny greenish-white swellings or galls. Later, the exposed surface of the swellings becomes rust-colored with a corky texture. Oedema is a condition promoted by abundant soil water and a cool, moist atmosphere. Under these conditions roots absorb water faster than it is lost through the leaves. Excess water accumulates in the leaves. Prevention and Treatment: This problem is not caused by disease or insects. Oedema is caused by overwatering, especially during cloudy, humid weather. Water less frequently and avoid overcrowding plants to increase air movement.

Note: Control of diseases and insects on large trees is usually not feasible, since adequate coverage of the foliage with a pesticide cannot be achieved.

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