Sooty mould on ponytail palm


Hi- You diagnosed my palm with sooty mould. (see link below) Have washed and wiped the plant and removed the dead stems which are primarily on the lower stems. The mould is primarily where the leaf joins the main trunk.The problem is I can’t find any bug infestations, so I don’t know exactly what the plant has. I need some product names for insecticidal soaps. Located something called Neem Oil and Neem oil insecticide used as a soil drench. Can you please advise?

Sooty Mould on Ponytail palm


We are not permitted to recommend particular brands of any product, but if you check with your local nursery, they should have several available.

Both insecticidal soaps and neem oil* kill only those aphids that are on the plant at the time it is sprayed, so repeat applications are usually required.  As well, the plants need to be covered thoroughly in the soap or oil to prevent resurgence of the insects.  Be especially careful to target areas where the leaves join the trunk and other hiding places for aphids.  Be patient – it may take some time for you to be certain that the insects will not return.

Insecticidal soaps are potassium salts of fatty acids. They are not toxic to animals or most plants, and kill insects in 2 ways: first by washing away the hard protective coating on the insect’s body and causing dehydration, and second, once inside the insect, the soap attacks the cell membrane, eventually killing the cell.  These soaps work best on insects that have soft bodies – this includes aphids, which excrete the sap that the sooty mold feeds on.  These soaps are also helpful as leaf washes to remove sooty mold from leaves.  Some plants, including palms, may be injured by insecticidal soaps, so it’s best to test spray a spot on the plant first — if there are no symptoms after a week, spray the entire plant.

See Penn State’s Insecticidal soap  and the University of Connecticut’s Insecticidal soaps for more detailed information.

See also the University of California’s Pests in gardens and landscapes – sooty mold.

*Special note on Neem Oil. It is not a registered product for use as a pesticide. Please listen to this link for further explanation:

CBC. Gardening. Is neem oil banned? 2016 (Ed Lawrence, Health Canada expert Lindsay Hanson)

All the best in keeping Eyeore healthy!