A Blight on Camellia Flowers

by Andrea Laine, EMGV

Is it worth growing camellias if all the flowers turn brown and crispy, sometimes even camellia blightbefore fully opening? That’s the question I’ve been pondering the last few months because my shrubs suffer camellia flower blight.

Camellia flower blight is caused by the fungus Ciborinia camelliae. The first sign of the fungus is small brown spots on the petals. As the spots quickly enlarge, the flower turns brown and may drop to the ground. Eventually the fungus invades to the flower base where, according to the American Camellia Society, a hard, black structure called a sclerotium forms. I’ve not yet noticed the sclerotium; perhaps it is tiny or I am just grief-stricken over the sight of what were once beautiful pale pink blossoms.

The Ciborinia camelliae fungus reproduces by spores which are forcefully discharged into the air and dispersed by the wind. They can be carried several miles. Thankfully, the disease affects only the flowers, not the roots, stems or leaves, and only camellia flowers, not any others that may be in bloom at the same time. This news is of little consolation though because the spores, which emanate from sclerotia,  can lie dormant in the soil for one to five years or more. Camellia growers have been battling blight since the 1950s.

camBlightSpores
The sclerotia germinate to produce tiny mushroom-like structures. The “mushrooms” produce airborne spores that land on nearby camellia flowers, starting a new cycle of disease.

Two well-established camellias in my garden have the blight. These bushes typically begin blooming in February. Three years ago I was told by a seemingly reliable source that flower blight only affected the spring blooming camellias, but this is incorrect; all camellias are susceptible. However, weather conditions are generally not favorable for the fungus to germinate when Camellia sasanquas bloom in the fall. Spores germinate rapidly when a period of cool weather is followed by warmer temperatures and moist conditions. (Sounds like early spring, doesn’t it?) I have several fall-blooming camellias growing in another part of my yard and they are not affected by blight.

Because eradicating the fungus seems nearly impossible, I decided to keep just one of my blighted Camellia japonicas. The one I choose to nurture is larger, in better general health than the other, and occupies a prominent place near the front entrance to my home.

I hope to control the spread of the disease by practicing good sanitation. I collect and trash the diseased blooms. (Never compost diseased blooms!) Beginning this spring, I removed and replaced old mulch around the base of the camellia. Note that a one-inch layer of mulch is enough for camellias; more is not better and could kill the plant. Applying a systemic fungicide is also an option. All methods need to be continued for at least five years after the symptoms first appeared with no promise of actually curing the blight.

Resources
Camellia Diseases & Insect Pests
https://hgic.clemson.edu/factsheet/camellia-diseases-insect-pests/

Control of Camellia Petal Blight, including chemical options
http://www.aces.edu/pubs/docs/A/ANR-0416/ANR-0416.pdf

From the American Camellia Society
https://www.americancamellias.com/care-culture-resources/insects-and-diseases/camellia-petal-blight

Image of the mushroom-like structures produced from sclerotia germination
http://ncsupdicblog.blogspot.com/2011/03/be-on-lookout-for-camellia-petal-blight.html

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