I have a schefflera that is 20 years old. It has started to “weep” a sticky sap like substance. This has now spread to my palm plants as well. On the leaves of the palms there are small brown nodules also.
It sounds like you have a problem with an insect called scale. These pests have a hard outside coating that makes them appear to be brown nodules. They are most frequently found on the underside of leaves.
The sticky sap that you find is actually secreted by the scale and is called honeydew, an oddly appealing name for such an unappealing substance.
It’s amazing to me how these pests can just suddenly show up. One day the plant looks fine and the next day it’s infested. So how do you handle such a problem in a safe way?
The first thing you should do is isolate your infected plants from your healthy plants.
One way to kill an infestation is to simply use a cotton swab and rubbing alcohol. Dip the swab in the alcohol and brush it on the scale. One touch with the alcohol is all you need. Another way to remove scale is to use an insecticidal soap. You can buy this at a garden center. Follow label instructions. Contact with the soap begins to break down the outer covering of the insect’s body, exposing it to the elements. Now the nice thing about this is that it is made of fatty acids so it won’t harm children or pets.