Scale is a common pest of many houseplants, including ficus, schefflera, ivies, pothos, citrus, spider plants, and palms. (Outdoors, scale can infest many plants, including fruit trees.) Carefully inspect newly purchased houseplants--or those being moved indoors for the winter--and quarantine them for 3 weeks to ensure they haven't come with any piggybacking pests.
"Since their thick, shell-like coat is tough to penetrate, scales can be difficult to control," Davis says. "The best nontoxic method is manual removal." Crush the insects with a cotton ball or cotton swab soaked in isopropyl alcohol and continually monitor the plant for further infestations. Commercial preparations of insecticidal soap are effective, too. Use a sprayer to apply it to all plant surfaces every 7 to 10 days for 2 months. And, until the scale is gone, keep infested plants away from healthy ones.
Photo: United States National Collection of Scale Insects Photographs Archive, USDA Agricultural Research Service, Bugwood.org