ANR-416, Revised May 1997. Austin Hagan, Extension Plant Pathologist, Professor, Plant Pathology, Auburn University

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Control Of Camellia Petal Blight

Camellia petal blight, caused by the fungus Ciborinia camelliae, can be a damaging disease on both common and sasanqua camellia. Disease development is favored by frequent rain showers, high humidity, and mild temperatures during bloom. All cultivars of camellia are equally susceptible to this disease. Camellia petal blight is introduced into landscape plantings on diseased plant material.

Symptoms

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 leathery but do not crumble when handled. Once the blooms are killed, they will fall intact to the ground.

Disease Cycle

Small black bodies, called sclerotia, appear at the base of the blighted petals several weeks after the blooms fall to the ground. Black sclerotia are usually seen on the decaying petals. The following fall or winter, some sclerotia may produce a small, mushroom-like structure, called an apothecia, while others remain dormant for up to 5 years. Spores, which are released by the apothecia, are spread to camellia flower buds by wind currents, germinate under favorable weather conditions, and rapidly infect the petals.

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Control Practices

Once introduced into a planting of camellia, the causal fungus cannot be eradicated. A combination of sanitation, cultural practices, and fungicide treatments may be required to control camellia petal blight.

• Collect and destroy all diseased blooms on and beneath the plant.
• Each spring, remove the old mulch, and then lay a layer of 1 inch of fresh bark or pine straw mulch around the base of each camellia. The mulch will interfere with the spread of spores from the apothecia to the flower buds. Be sure not to over-mulch camellia; burying the root system under 2 or more inches of mulch may kill the plant.
• 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.

Fungicides, applied as a soil drench, will prevent the development of the apothecia on the surface of old mulch or soil beneath the plants. For effective control, apply enough fungicide mixture (usually 2 or more quarts) to the soil surface to soak a 10-foot circle around each plant. Make the first fungicide soil drench about 2 to 3 weeks before the buds begin to open. Repeat the fungicide soil drench twice at 3-week intervals. Treatments should be continued annually for 5 years after symptoms were first seen. Recommended fungicides are listed in Table 1.

Table 1. Chemical Control Of Camellia Flower Blight.

	Rate
Fungicide	per gal.	per 100 gal.	Comments
Foliar Sprays
mancozeb Dithane T/O 80W Fore 80W Protect T/O 80W	2 t. 2 t. 2 t.	1.5 lb. 1.5 lb. 1.5 lb.	Apply when blooms show color and repeat at 10- to 14-day intervals. Also, spray ground under plant.
thiophante-methyl 3336 50W 3336 4.5F	- 1/2-1 T.	12-16 oz. 10-20 fl.oz.
triadimefon Bayleton 25W	-	8-16 oz.	Make first application when buds show color and repeat at 7- to 14-day intervals.
Soil Drenches
PCNB Terraclor 75W Defend 75W	- -	1 c./100 sq.ft. 1 c./100 sq.ft.	Spray or dust around base of plant. Apply enough water to cover area in late November to mid-December.

Foliar sprays of selected fungicides will provide additional protection from camellia petal blight, particularly in valued landscape plantings. The first applications should be made when the buds begin to show color. Repeat the foliar sprays during bloom at the rates and intervals listed in Table 1. Spray the ground under each plant with any remaining fungicide spray mixture in the spray tank.

The pesticide rates in this publication are recommended only if they are registered with the Environmental Protection Agency and the Alabama Department of Agriculture and Industries. If a registration is changed or cancelled, the rate listed here is no longer recommended. Before you apply any pesticide, check with your county Extension agent for the latest information.

Trade names are used only to give specific information. The Alabama Cooperative Extension System does not endorse or guarantee any product and does not recommend one product instead of another that might be similar.

For more information, contact your county Extension office. Look in your telephone directory under your county's name to find the number.