Q: My camellia flowers normally stay on the tree for a long period of time but a few of the flowers turn brown and drop off quickly. What is wrong?
A: There are environmental reasons for browning of camellia flower petals such as cold temperatures, too much sun or severe wind exposure. However, there is a serious disease of camellias which can cause the flower petals to turn brown. It is easy to distinguish the difference between the disease and environmental causes as the fungal disease causes the vascular tissue to be darker than the surrounding petal tissue.
The first sign of the fungal disease will be spots on the petals but the spots soon spreads to the rest of the petal tissue and then to the center of the flower at which time it is called flower blight. As with any disease the conditions for the pathogen (fungus) have to be perfect. Early spring rains often provide that perfect environment for the fungus, Ciborinia camelliae, to damage the petal tissue. Ultimately the entire flower turns brown and the flower usually drops within 24 to 48 hours. Only the flowers of the plant are affected.
The best management is sanitation. Remove all diseased flowers and especially those which have dropped off the tree. This fungus lives in the soil so it is best to remove and replace old mulch when the disease is detected in a camellia plant. Fungal soil drenches are available which will be absorbed by the roots and transferred to the rest of the plant helping to maintain long term control. Topical fungal sprays are also available which can be sprayed directly on the flowering portion of the plant. As always, please follow the directions on the label for best results.