Camellia japonica are camellia shrubs native to Japan and other parts of Asia. Camellia japonica needs partial sun or filtered light and moist soils in which to thrive, according to Floridata. Most types of camellia are hardy through USDA zones 6 to 9. Some of the camellias growing around the Emperor's Palace in Japan are over 500 years old.
Camellia Dieback & Canker
According to Clemson University, Camellia dieback & canker is caused by the Glomerella cingulata fungus and causes the leaves of the Camellia japonica to turn yellow and wilt. Also, the tips of the branches die and gray spots appear on the branches, followed by cankers. To treat this disease, cut off the diseased foliage several inches away from the cankers and use a fungicide.
Camellia Flower Blight
The fungus Ciborinia camelliae causes this problem when it is very moist during the spring. It turns the Camellia japonica's flowers brown and they fall off of the plant in one to three days. Remove all infected flowers as you see them and destroy them.
This is a common plant disease caused by the Phytophthora cinnamomi fungus. It turns the leaves on the Camellia japonica yellow and eventually the whole plant wilts and dies. Prevention is usually the only way to save a plant with this disease, so plant Camellia japonica in areas with good drainage.
Camellia Yellow Mottle Virus
This virus causes yellow spots on the leaves of the Camellia japonica. It may also cause some leaves to turn entirely yellow. There is no cure for this virus, so it is best to buy plants that do not have any yellow leaves.