(Exobasidiaceae the redleaf fungi family)
Camellia sasanqua can occasionally be infected with a particularly ugly fungal disease called Camellia Leaf Gall, (Exobasidium camelliae). Plants become susceptible to fungal infection when conditions are not optimal for the plant's natural defences to fight the attack. This might be due to unsuitable soil conditions, the amount of light that the plant receives, the climate, watering regime, or even factors beyond control such as unusual or adverse weather. Rarely, Camellia retiiculata can also suffer from Camellia Leaf Gall.
Identification: The infection takes hold when the leaves are begining to form. The Camellia Leaf Gall fungus causes some of the leaf-cells to grow much larger than normal and divide more than normal: resulting in the infected leaves looking like large, ugly, succulent fleshy swellings sometimes with a reddish or pinkish hue. Whilst the upper surface looks almost normal in colour, the underside of the leaf is white which is a part of the protective membrane enclosing the Exobasidium fungal spores.
Control: In archaic gardening books it was once recommended to spray Camellia Leaf Gall with a low-lime bordeaux mix but with our current awareness of the biological and environmental dangers of chemical use, coupled with the limited efficacy of this approach means that this method of control is depreciated.
The best practise¹ for control of Camellia Leaf Gall (and for most other fungal diseases) is to:
Red Spider Mite: From my observations of infected shrubs, I suspect that the Red Spider-Mite, Tetranychus urticae (pictured right) might contribute to the spread of Camellia Leaf Gall Exobasidium camelliae.
Prevention: Preventative strategies include;
 Best Practise or Best Biological Practise, means what is the safest method for You and for the environment in dealing with any given horticultural situation.