Answer: Camellia petal blight, caused by the fungus Ciborinia camelliae can be a damaging disease on both common and sasanqua camellias. The disease development is favored by frequent rain showers, high humidity, and mild temperatures during bloom. All camellias are equally susceptible to this disease.
Within 24 hours of infection, small brown spots appear on the expanding flower petals, The veins, which usually are darker than the surrounding tissues, often give the blooms a distinctive netted appearance. This netted pattern can be used to distinguish petal blight from cold injury. These spots quickly increase in size until the entire bloom turns a dull brown. The blighted petals are dry or somewhat leathery but do not crumble when handled. Once the blooms are killed, they will fall intact to the ground.
A combination of sanitation, cultural practices, and fungicide treatments usually are required to control camellia petal blight.
Collect and destroy all diseased blooms on and beneath the plant. Each spring remove any old mulch or top dressings, and then lay a 1 inch layer of fresh bark or mulch around the base of the camellias. The bark or mulch will interfere with the spread of spores from the apothecia to the flower buds.
Foliar sprays and drenches of selected fungicides may give some protection from camellia petal blight and should only be used in conjunction with the sanitation and cultural practices already described.
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