Sticky Residue on Houseplant? It's Scale Insects

Mitra has a large unknown plant in a medium pot with 6–8 leaves per stem. Sticky residue drips onto the floor, and leaves have black and brown removable spots.

Expert Answer: The spots are scale insects—brown ones are alive, black ones dead. The stickiness is their excrement (honeydew). Mix 2 parts rubbing alcohol, 1 part water, and 1 tablespoon dish soap per quart. Spray tops and bottoms of all leaves daily for 5 days, then twice weekly for 3 weeks. Afterward, wipe dead scale off with an alcohol-dampened cloth. Monitor closely for recurrence. The plant may be a large dieffenbachia or dracaena; check images online or send a photo for ID.