Cause Both a genetic variegation and a viral infection can produce this effect. Neither seems detrimental to the plant; some propagators even desire them. There are 3, maybe 4, different viruses that have been associated with this symptom and have been provisionally named camellia ring-spot associated virus 1 through 4. (Former names may include camellia leaf yellow mottle virus or camellia infectious variegation virus). These virus particles are flexuous and filamentous. Additional viruses have been described and provisionally named camellia japonica-associated emaravirus 1 and 2. These viruses can be graft-transmitted into other camellia plants and seed transmissible as well. Cutting taken form infected plants will also contain the virus(s).
Symptoms The genetic variegation produces regular white or pink stripes in flowers. On some branches, a flower can revert to normal.
The viral variegation produces irregular white spots or blotches, mottles, mosaics or ringspots. Some of the leaves are almost entirely affected. Margins of affected areas are not distinct and blur into the normal color of the plant part. The mottling symptoms vary from mild to severe, and their appearances are even, marginal, or irregular. Different sizes and shapes of light-green, yellowish or necrotic ringspots with surrounding islands of green on the leaves are frequently observed. The pattern of affected plant tissue also is irregular on the whole plant; some branches show symptoms, others do not. Symptoms may or may not appear every year.
Yellowing leaves on large portions of the plant may be indicative relatively high soil pH.
Cultural control
- If the viral variegation is not desired, then purchase virus-tested (and found to be free of all known viruses) plants to start.
- Check soil pH which should be between 5.5 and 6.5 if yellowing leaves are a common and consistent problem on bushes. Home gardeners should fertilize with products marketed as azalea, camellia and/or rhododendron food.
- Viral symptoms are reported to be reduced when supplemental iron was applied to the media of potted plants.
References Bond, E.R. 1994. Camellia variegation. American Nurseryman, Sept. 15, p. 50-51.
Liu, H., Wu, L., Zheng, L., Cao, M., and Li, R. 2019. Characterization of three new viruses of the family Betaflexiviridae associated with camellia ringspot disease. Virus research, 272:197668.