What Is the Black Fungus on a Gardenia?


The black fungus that appears on some gardenias is actually a form of mold. It appears as black soot or ash and is mainly present on the leaves.

Sooty Mold

Sooty mold is caused by an infestation of some insects. The insects that produce the black fungus include white flies, aphids and mealy bugs.

White Flies

White flies are tiny insects that resemble moths. They excrete sticky honeydew from their bodies that causes the black soot to appear on plants.

Aphids and Mealy Bugs

Aphids and mealy bugs may also cause the sooty mold to occur on plants. They also produce a sugary substance that produces the mold.

Getting Rid of the Sooty Mold

In order to get rid of the sooty mold, all that is required is an insecticide that targets the fungus-causing insects.


Continue to check the plant a week after treatment. Once the infestation has been dealt with, the plant should begin to heal and grow normally.


  • GreenShare: Factsheets
  • Gardening Know How: Removal
Keywords: sooty mold, gardenias, infestations

About this Author

Fay Sawyer has just earned a Bachelor of Arts from Indiana University, where she was an English major with a concentration in creative writing. It was Sawyer's years in college that taught her the art of creating the written word.