Camellias are an attractive evergreen shrub, especially in full bloom. These plants have inspired a dedicated following of gardening enthusiasts around the world who have studied the plant thoroughly. The nature and causes of camellia diseases are therefore well documented, although this has not led to any treatment breakthroughs. Prevention is very much the order of the day.
Petal blight is perhaps the most common of all camellia diseases as it can affect all species and varieties. It is caused by ciborinia camelliae, a fungus that is found in soil. The spores of the fungus are carried by the wind and are only known to attack camellia flowers. The first symptoms are small brown spots appearing on the petals. There is no successful treatment for this disease, making prevention the only option. Plants should be carefully examined before transporting them to prevent the spread of the fungus. Dead or infected flower tissue should be burned, and definitely not composted.
Leaf Gall is a disease that mainly affects the sasanqua species of camellia. It is caused by the fungus exobasidium, which only attacks new growth. Since the main plant remains healthy and the affected area will clear up within a few weeks if left alone, no treatment is recommended.
Camellia canker is a problem in hot areas with high humidity and in greenhouses. It is caused by glomerella cingulata, a fungus that is native warmer regions. All camellia species are susceptible to this ailment. Cankers appear on branches and stems causing the foliage above to die back. The fungus attacks the plant through wounds, which can include pruning cuts. Applications of fungicide have proven effective as a preventative but not as a cure. Infected plants should be separated from healthy stock and all infected parts of the plant need to be removed and burned.
The principal cause of root rot in camellias is a soil-dwelling fungus known as phytophthora cinnamomi. The fungus progressively attacks the root system and spreads through. Plants that are wilted or showing signs of discoloration may already be affected. The best preventative is keeping plants in well drained soil since the spores of the fungus are water-borne and will move quickly through saturated soil. Another fungus, cylindrocladium crotalariae, is found in river sands and is dangerous to cuttings and seedlings. Be sure to use sterile sand when propagating. Mature camellia plants are not affected by this fungus.