Nelson Hall confirmed our fears. The tiny, mushroom-like apothecia of Ciborinia camelliae were popping out all over (below).
These tiny mushrooms bear the spores that infect the camellia blossoms. We generally miss the chance to spray for petal blight, but if you can catch it just as the apothecia emerge, you might be able to control it with fungicides. Later, the best control is to pick up all the spent and diseased blossoms as soon as they fall to the ground. This will reduce the number of apothecia that are produced the following spring.
For more information about petal blight, see our earlier blog post here.
For information about fungicides that control petal blight, see http://www.aces.edu/pubs/docs/A/ANR-0416/ANR-0416.pdf
Be sure to check with your local County Extension office to get the latest information about fungicide labels and use. Follow all label directions.