Gardenia has a disease - Knowledgebase Question

Commerce, Ge
Question by shirleymc
March 12, 2010
My gardenia shrubs have a disease. Most of the leaves have fell off and the leaves that are left are getting black. Is this a fungus or a disease.

Answer from NGA
March 12, 2010


If the black on the leaves is on the surface (you can scrape it off with a fingernail) it is sooty mold, the result of insect feeding. Aphids, scale insects and mealy bugs can all cause this. As they feed they exude a sticky substance called honeydew which eventually turns black. Scales and mealybugs are difficult to control. Sometimes it's easier to simply prune away all the affected foliage to get rid of them and to restore your plant to good health. However, if the black is actually the leaf itself, it indicates a salt burn problem - overfertilizing is the usual cause. If the plant is in the ground you can try flooding the soil to leach out excess salts. If it is in a container you can simply repot it in fresh potting soil. Whatever the cause, you'll want to prune off the affected plant parts to give your gardenia a second chance. Good luck with your gardenia.

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