• Spider mites are the number one interior problem to watch for. 
• Mealybugs may be a minor problem indoors
• Aphids may be a minor problem outdoors
• Older leaves turning yellow is a sign of water stress
• Black aralias require less water than most of our other aralia varieties.

Mites should be primarily controlled with predator mites.  Neoseiulus californicus,(Spical, Spical Plus, Californiline) and Phytoseiulus persimilis,(Spidex, Bio Persimilis, Phytoline) are two excellent choices for spider mite control.  If a mite infestation is exceptionally bad, prior to the release of predator mites, spray the plant with water or horticultural oil.  Both will provide some knockdown control of spider mites and will not leave a toxic residue that may effect predator mites.  Miticides registered for interior use and compatible with predator mites include Sultan, Shuttle O and Floramite SC.  

Mealybugs can be removed with a systemic insecticide drench and hand cleaning.  If pesticides are not an option, try horticultural oil directly sprayed onto the insects.  A second and third treatment, if using oils,  will be necessary.  Space out the sprays at 3 week intervals to break up the mealybug life cycle.  

Aphids can be controlled with the same treatment as mealybugs.

Edema is a condition where a plant is taking up water faster than it can transpire causing leaf cells to rupture.  Black aralias can have a problem with edema, but to a lesser extent than other types of aralia.  Corky spots on the leaf are signs that the plant suffered this condition in the past.  Edema can be controlled by varying the amount of water the plant has available.  Basically, don't provide excess water.  In the nursery, edema problems can be difficult to prevent during the rainy season.  Don't  worry, it does not spread, and it won't hurt the plant in any way.

Sometimes the foliage of the Black Aralia may revert to the standard Polyscias guilfoylei.  This different looking foliage can either be left or removed.

To recuperate an Aralia that has lost too many leaves, trim each small stem about 2 inches from the woody cane, fertilize and place in a higher light environment.

Other Links:

Horticultural Oils

Safari Pesticide Label