| Disease (causal agent) | Symptoms | Survival of pathogen and effect of environment | Comments on control |
|---|---|---|---|
| Dieback (Glomerella cingulata) |
Wilting and dying of branches. Leaves darken and often remain attached. Branch is girdled by fungus that enters through injuries, including leaf scars. | Found in warmer areas of California. Favored by wet, warm conditions, weakened plants, and injuries. Fungus spores (conidia) are spread by splashing water. Fungus has a wide host range. | Prune diseased tissues and protect wounds with a fungicide such as captan. Avoid overwatering. |
| Flower blight (Ciborinia camelliae) |
Flowers have dry rot with accented veins. Only petal tissues are infected. First symptoms are small tan or brown necrotic spots in the center of the flower that enlarge and move rapidly to the base of flower. Rotted flowers are heavy and easily fall to ground. The fungus continues to develop, forming sclerotia in the calyxes of infected flowers. | Sclerotia survive on or in soil and germinate for several years producing fruiting bodies (apothecia) that discharge spores (ascospores) forcibly into the air. | Where practical, pick up all blossoms because fallen blossoms either may be infected or may become infected while on the ground. Prevent sclerotia from germinating by spraying ground with PCNB annually. Thiophanate-methyl will protect petals from infection but sprays must be applied frequently as new flowers open. Mulches 4 inches or more deep will help prevent apothecia from reaching the surface. |
| Gray mold * (Botrytis cinerea) |
Necrotic, brown spots. Rot does not move to the base of the flower as rapidly as the flower blight fungus. Fuzzy gray fungus spores form on decayed blossoms under high humidity. | Favored by cool wet weather. Spores are airborne. Fungus survives on and in old flowers. | Avoid overhead irrigation. Clean up plant debris, especially floral tissues. Protect flowers with a fungicide effective against Botrytis such as fenhexamid. |
| Ramorum blight 1
(Phytophthora ramorum) |
Leaf lesions that vary in size from 0.2 inches to covering nearly half the leaf. Lesions primarily at leaf tip or edge; can be surrounded by diffuse margins or thick black zone line. Infected leaves drop prematurely and lower part of plant can defoliate. Symptoms may be confused with leaf scorch in areas of high heat/sun. | Spore structures commonly form on leaf surfaces of susceptible leaves and twigs following prolonged wetting. They are moved in contaminated soil, from plant to plant via windblown rain, or by direct contact of infected leaves. | Monitor incoming stock and areas surrounding the nursery for symptoms, follow good cultural and sanitation practices, and use preventive treatments before environmental conditions favor development of the pathogen. |
| Phytophthora root rot * (Phytophthora spp.) |
Plants stunted and low in vigor. Foliage yellows, plant wilts and dies. Roots rotted. When plants collapse, the stem is girdled at or below the soil line. Phytophthora cinnamomi is often involved but other species also infect camellias. | Phytophthora spp. survive in soil as resting spores. They are common in stream and ditch water. Infective spores (zoospores) swim very short distances in soil water. Disease is favored by poor drainage, long wet periods, and standing water. | Heat or chemically treat propagation and growing media. Drench plants on a preventative basis with oomycete (water mold) specific fungicide. |
| Camellias are also susceptible to several viruses and viroids such as color break virus and golden ring spot complex.* | |||
| * For additional information, see section on Key Diseases. |
| 1 Phytophthora ramorum was isolated from the following C. japonica cultivars on two or more occasions: Bob Hope, Mrs. Charles Cobb, Daikagura var. Debutante, Elegans Splendor, Glen 40, Kumasaka, Kramer's Supreme, Mathotiana Supreme, Nuccio's Gem, Nuccio's Pearl, Silver Waves, Shiro Chan, Tom Knudsen, P. ramorum was isolated from the following C. sasanqua cultivars on two or more occasions: Apple Blossom, Cleopatra, Hana Jiman, Jean May, Kanjiro, Setsugekka, Yuletide. P. ramorum was isolated from the following C. oleifera cultivar on two or more occasions: Winter's Fire. |