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.
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 or copper-based fungicides 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. See Table 1 for examples of products.
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.
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, best control is achieved when controls are applied to other camellia plants in the landscape.
Fungicide sprays recommended for the flowers include mancozeb. Application of soil drenches, such as mancozeb or captan, around the plant every 2 weeks from late December through January may be helpful in reducing the intensity of disease. See Table 1 for examples of products. 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 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 soil-applied 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 Japanese camellia (C. 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. Later the galls 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.
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, 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. See Table 1 for examples of products. 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.
Prevention & Treatment: There is no chemical that will cure the virus. Plant only virus-free plants obtained from a reputable garden center.
Algal Leaf Spot: The parasitic alga Cephaleuros virescens is the most common causal agent of algal leaf spot on camellia and other shrubs and trees. Algal leaf spots may be circular or blotchy in shape, and they are slightly raised from the plant surface.
The edges of the spots may be wavy or feathered. These spots may vary in color from a crusty gray-green to greenish brown. However, in summer when the alga is reproducing, the spots take on a velvety, red-brown appearance due to the production of reddish, spore-producing structures. If colonies are numerous, premature yellowing and loss of leaves can occur. For more information and control measures for alga leaf spot, please see HGIC 2060, Algal Leaf Spot.
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.
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 plant death.
Tea scale (Fiorinia theae) is the most serious scale insect on camellia. This scale attaches to feed on 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 long. 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.
Cottony camellia scale (Pulvinaria floccifera) is a soft scale that infests not only camellia, but also holly, hydrangea, English ivy, euonymus, maple, rhododendron, yew, and pittosporum. The adult scale is flat, 1/8-inch in diameter and yellowish-tan. As with other soft scales, cottony camellia scale produces large amounts of sugary honeydew, which both attracts ants and causes the leaves to become covered with black sooty mold.
The adult cottony camellia scale females lay ovisacs, which are the cottony white egg masses, during the early summer. The eggs hatch in summer, and the crawlers (small mobile immatures) will move around on foliage to find a place to feed on the lower leaf surfaces. Foliage with a heavy infestation may turn pale green or yellowish.
Prevention & Treatment: 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 refined horticultural oil is in late winter or early spring, and the danger of cold weather has passed. This will kill many adults, crawlers, and eggs by smothering them.
Apply horticultural oil sprays at a 2% solution (5 tablespoons oil per gallon of water). Spray the plants thoroughly, so that the oil spray drips or “runs off” from the upper and under sides of leaves, twigs, and plant stems. Spray when temperatures will be above 45 °F for the next 48 hours. Spray when no rain is in the forecast for 24 hours.
Spraying an insecticidal soap later during the growing season will help control crawlers, as well as adults. Spray two applications, 10 days apart. Spray when the temperature is between 45 and 90 degrees, and spray in the evening to slow soap drying time and to increase effectiveness. See Table 1 for examples of brands of horticultural oils and insecticidal soaps.
Most contact insecticides are effective only against the crawlers. In addition, using a contact insecticide against scales can result in the deaths of naturally occurring enemies of scales (predators and parasites). As such, contact insecticides generally should be avoided if possible.
With tea scale, crawler activity coincides with the flush of new plant growth in the spring, but with cottony camellia scale, crawlers emerge in early summer. To determine when to best spray with a contact insecticide (or an insecticidal soap), 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. However, some scale species may have overlapping generations with an extended crawler emergence period, such as along the South Carolina coast.
Insecticides labeled for homeowner use against scale crawlers (only) include acephate, malathion, cyfluthrin, bifenthrin, cyhalothrin, and permethrin. Of these insecticides, acephate may give the best control, as it is a foliar systemic insecticide. See Table 1 for examples of products. As with all pesticides, read and follow all label instructions and precautions.
A soil application can be used once in the spring around the base of the infested plant with a product containing dinotefuran to control both soft and armored scales. See Table 1 for examples of products, which may be found at landscaper supply stores. Read and follow all label instructions and precautions. Soil applications may be used in addition to sprays with horticultural oil or insecticidal soap. Note: Soil applied products containing imidacloprid do not effectively control armored scales, such as tea scale, or soft scales, such as cottony camellia scale. On evergreen shrubs like camellias, dinotefuran may be applied either in the early spring or early fall.
Bud Drop: Camellia flower buds may drop from the plant before opening, or the tips of the young buds may 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 from a lack of nutrients or poor 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 it may 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: Oedema (sometimes spelled edema) is a physiological disorder of camellia leaves due to excessive water uptake by the roots and a reduced ability of the foliage to transpire (or give off) this buildup of water. The symptoms of oedema will occur primarily on the lower leaf surfaces, and at first appear as small, water-soaked, greenish-white raised areas.
Eventually as the water pressure builds up in the lower leaf tissue, the blisters will erupt into rust-brown or yellow-brown, corky, wart-like layers of dead ruptured cells that are most characteristic of this disorder. Oedema typically occurs in late-winter or early spring following wet, cool weather. With the cool temperatures, extended cloudy weather, and higher relative humidity, camellia plants will take up much more water than they can transpire. It is important to recognize that this condition, although unattractive on the foliage, does not significantly harm the health of the plant, and no spray control measures are required or effective.
Prevention & Treatment: Control measures include improved air movement around the plants, and an increased level of sunlight by pruning back adjacent plants and over-hanging tree limbs. If irrigation is being employed, monitor the soil moisture levels, so as to not over-water these and other shrubs. Make sure new camellias are planted on well-drained soil, and maintain proper soil fertility through soil testing.
Note: Control of diseases and insects on large shrubs and trees is usually not feasible, since adequate coverage of the foliage with a pesticide cannot be achieved.
Table 1. Fungicides & Insecticides to Control Camellia Diseases & Insect Pests.
|Active Ingredient||Examples of Products|
|Acephate||Bonide Systemic Insect Control Concentrate|
|Bifenthrin||Ortho Bug-B-Gon Insect Killer for Lawns & Gardens Conc.; & RTS1
Ferti-lome Broad Spectrum Insecticide Concentrate
Hi-Yield Bug Blaster Bifenthrin 2.4 Concentrate
Monterey Turf & Ornamental Insect Spray
Bifen I/T Concentrate
Talstar P Concentrate
Up-Star Gold Insecticide Concentrate
|Captan||Southern Ag Captan Fungicide WP
Bonide Captan 50% WP
Drexel Captan 50W
Arysta Captan 50% WP
Hi-Yield Captan 50W Fungicide
|Copper Fungicide||Bonide Liquid Copper Concentrate (1.8%)
Camelot Fungicide/ Bactericide Concentrate (1.8%)
Natural Guard Copper Soap Liquid Fungicide Concentrate (1.8%)
Bonide Copper Fungicide Spray or Dust (7%)
Monterey Liqui-cop Fungicide Conc. (8%)
Southern Ag Liquid Copper Fungicide (8%)
|Cyfluthrin||Bayer Bio Advanced Vegetable & Garden Insect Spray Concentrate; & RTS1|
|Dinotefuran||Ortho Tree & Shrub Insect Control Ready to Use Granules (2%)
Valent Brand Safari 2G Insecticide (2% granules)
Gordon’s Zylam Liquid Systemic Insecticide (10%; drench2)
Gordon’s Zylam 20SG Systemic Turf Insecticide (20%; drench)
Valent Safari 20SG Insecticide (20%)
|Horticultural oil3||Ferti-lome Horticultural Oil Spray Concentrate
Bonide All Seasons Spray Oil Concentrate
Southern Ag ParaFine Horticultural Oil Concentrate
Espoma Earth-tone Horticultural Oil Concentrate; & RTS1
Monterey Horticultural Oil Concentrate
Summit Year Round Spray Oil Concentrate
|Lambda or Gamma Cyhalothrin||Spectracide Triazicide Insect Killer for Lawns & Landscapes Conc.; & RTS1
Martin’s Cyonara Lawn & Garden Concentrate
|Malathion||Spectracide Malathion Insect Spray Concentrate
Southern Ag Malathion 50% EC
Hi-Yield 55% Malathion Insect Spray Concentrate
Tiger Brand 50% Malathion Concentrate
Gordon’s Malathion 50% Spray Concentrate
Bonide Malathion Insect Control 50% Concentrate
Martin’s Malathion 50% Concentrate
Ortho Max Malathion Insect Spray Concentrate
|Mancozeb||Bonide Mancozeb Flowable with Zinc Concentrate
Southern Ag Dithane M-45
|Permethrin||Bonide Eight Insect Control Vegetable, Fruit & Flower Concentrate
Bonide Total Pest Control Outdoor Concentrate
Hi-Yield Indoor/Outdoor Broad Use Insecticide Concentrate
Bonide Eight Yard & Garden RTS1
Tiger Brand Super 10 Concentrate
Martin’s Vegetable Plus Concentrate
|Thiophanate Methyl||Cleary’s 3336-WP Turf & Ornamental Fungicide
Southern Ag Thiomyl Systemic Fungicide
Note: Pollinating insects, such as honey bees and bumblebees, can be adversely affected by the use of pesticides. Avoid the use of spray pesticides (both insecticides and fungicides), as well as soil-applied, systemic insecticides unless absolutely necessary. If spraying is required, always spray late in the evening to reduce the direct impact on pollinating insects. Always employ cultural controls first, then use less toxic alternative sprays for the control of insect pests and diseases. For example, sprays with insecticidal soap, horticultural oil, neem oil extract, spinosad, Bacillus thuringiensis (B.t.), or botanical oils can help control many small insect pests and mites that affect garden and landscape plants. Neem oil extract or botanical oil sprays may also reduce plant damage by repelling many insect pests. If soil applied insecticides are used, make applications immediately after flowering to reduce the amount of insecticide exposure to pollinating insects. For more information, contact the Clemson Home & Garden Information Center.