This insect is a common pest of many garden and greenhouse plants. The 4-winged adult lays eggs on the undersides of leaves. The nymphs are the size of a pinhead, flat, oval shaped, and semitransparent, sometimes with white waxy filaments radiating from the body. Both immature and adult forms suck sap from the leaves. The nymphs are more damaging because they feed more heavily. Adults and nymphs cannot fully digest all the sugar in the plant sap. They excrete the excess in a fluid called honeydew, which often drops onto the leaves or plants below. A sooty mold fungus may develop on the honeydew, causing the leaves to appear black and dirty. Whiteflies are unable to live through extended periods of freezing weather. One species, the silverleaf whitefly, began causing serious damage to vegetable crops in the Southwest in 1990.
There is no completely effective remedy for whiteflies. You can gain some control by spraying with an insecticide containing malathion or diazinon, or an insecticidal soap or a horticultural oil spray every 7 to 10 days as necessary. Spray the foliage thoroughly, being sure to cover the upper and lower surfaces of leaves. Make sure your plant is listed on the product label.
