Wash the foliage outdoors with a hard spray from a garden hose or place houseplants in the shower to knock off as many whiteflies as possible. The University of California's Integrated Pest Management website states that vacuuming the foliage can further reduce the whitefly population. Place a vacuum bag into a plastic bag and freeze it to kill the insects.
Place yellow sticky traps, available at most garden centers, around Ficus houseplants to capture whiteflies, which are attracted to the color. Follow manufacturer's directions for disposing of the traps.
Spray horticultural oil or insecticidal soap on houseplants and garden-grown Ficus to kill the whiteflies if washing them off does not eliminate the problem. Spray the undersides of the leaves, where whiteflies congregate and lay their eggs. Neem oil is less toxic to beneficial insects but kills whitefly nymphs and reduces egg laying. Make sure the product is labeled safe for houseplants if it is used indoors, and follow label directions for application frequency and dosage.
Spray the plants with a commercial insecticide. Look for products containing permethrin or pyrethrins, which are less toxic to beneficial insects, or products containing malathion or imidicloprid. Follow the label instructions for dosage.