My indoor plant (I looked it up and should be called: Heptapleurum Arbicola) is about 2″ tall and has been growing well for the last year. Most of the leaves look healthy but today I noticed that a few seem to have some sort of fungus on the under side (it almost looks like dirt). Wondering if it will spread to all or if I can simply remove the leaves that don’t look well. Thk you!!
Thank you for contacting Toronto Master Gardeners about your Heptapleurum arboricola. This plant was previously known as Schefflera arboricola, with the common names of Australian Ivy Palm, Parasol Plant and Umbrella Plant due to the leaf formation. This is an easy to grow indoor plant that can reach up to 5 – 6 feet tall. It does well in bright light with good soil drainage and occasionally dry periods after watering. As they say, it does not like “wet feet”.
Too much moisture could leaves the plant stressed and vulnerable to disease. Look closely for spider mite, aphids, mealybugs and thrips. Your photo shows brown spots on the underside of the leaves. This could indicate brown soft scale development, to which Schefflera arboricola is susceptible. Below is a link describing this infestation and how to manage it.
As far as managing Scale, the cautious and safe use of insecticidal soap or horticultural oils could take care of the infestation.
Another more sinister possibility is Bacterial Leaf Spot. Below is a previous Toronto Master Gardener answer to the presence of black spots and leaf drop on Schefflera. Fungicidal soap does not work on Leaf Spot and the plant must be discarded.
Further examination of your plant will give you a more definitive answer to the type of disease.
Good luck with your Schefflera.