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The blooming season for camellias is upon us, which is a time we need to look closely at these colorful plants. When camellias are blooming, they are most susceptible to the disease called Sclerotinia flower blight. This blight affects only the open blossom and does not threaten the health of the plant.
The disease invades the flower as soon as the tips of the petals are visible. The first sign of the fungus are small, irregular, brownish spots on the expanding flower. When late winter and early spring are warm and humid, the spots enlarge and soon consume the entire bloom. The bloom is then a dull brown and usually falls from the plant.
The fungus continues to develop in the fallen flower and eventually forms hard, irregularly shaped, dark brown to black bodies called sclerotia. These sclerotia endure through the winter and spores from them infect new flowers the following spring.
These sclerotia can lay dormant for several years until climatic conditions are appropriate for germination. When these conditions occur during camellia blooming, the sclerotia release spores that can infect open camellia blooms, thus further spreading the disease. Once this blight has become established, the problem becomes more difficult to control as it infects and spreads to more flowers and surrounding plants each year.
There are two methods of controlling this blight. The most important is sanitation. Remove any infected flowers from the plant and rake up all fallen blossoms from under and around the plant. Early next fall, replace all of the mulch with fresh mulch.
New flower infections can often be prevented by placing a 3-inch mulch of wood chips around the base of each plant. This provides a barrier that prevents the spores from blowing onto the leaves of the flowers. Be sure you do not pile the wood chips against the stem or trunk of the plant. Leave 4-6 inches around the trunk bare.
See the chart for a list of fungicides that can be applied to control the blight.
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 rate and intervals listed in table above. Spray the ground under each plant with any remaining fungicide spray mixture in the spray tank.
Use pesticides only according to the directions on the label. Follow all directions, precautions, and restrictions that are listed. Do not use pesticides on plants that are not listed on the label.
Recommendations for the use of chemicals are included as a convenience to the reader. The use of brand names and any mention or listing of commercial products or services does not imply endorsement by N.C. State University, N.C. A&T State University, North Carolina Cooperative Extension Service nor discrimination against similar products or services not mentioned.
Individuals who use chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure and examine a current product before applying any chemical.
Send your gardening questions or comments to: Brunswick County Master Gardener Column, P.O. Box 109, Bolivia, NC 28422, or call 253-2610. Enclose a self-addressed stamped envelope if requesting information or a reply. Answers may be printed in this column.