Mealy bugs are white, soft-bodied insects that suck plant juices. They are covered with white, waxy threads that protect them from predators. They are normally found where leaves join stems or along leaf veins, and their feeding will cause leaves to turn yellow and drop.
Plants most commonly affected by mealy bugs include aglaonema, most ferns, some palms, ficus, some draceanas, pothos, philodendron, Norfolk Island pine, schefflera, dieffenbachia, jade plant, African violets, streptocarpus and yucca.
Control mealy bugs by pruning infested branches and removing and destroying heavily infested plants. These pests may also be controlled with insecticidal soap. For heavy infestations, spray a mixture of 10 percent rubbing alcohol and 90 percent water directly onto the insects. For smaller infestations, dab the insects with a cotton swab dipped in rubbing alcohol. Repeat this procedure every week until the bugs are gone. Make sure to test the soap and alcohol mixtures on a small portion of the plant prior to full application because some plants may be sensitive to soap or alcohol.
Sprays of pyrethroid insecticides (tetramethrin, beta-cyflutherin, bifenthrin, permethrin) are usually effective for mealybug control. The soil-applied systemic insecticide imidacloprid can also be effective.
For more information, see the following Colorado State University Extension fact sheet(s).