IDENTIFICATION — If you brush the foliage of a plant and a white cloud floats up and quickly resettles, chances are your plant has whiteflies. Look on the undersides of the leaves and you’ll see the tiny white insects in the illustration.
DAMAGE — Larvae suck the sap from new leaves, which causes them to turn yellow and drop. Sometimes the young insects secrete sticky honeydew as they feed. The honeydew can harbor sooty mold, another symptom you may notice. It looks like black dust stuck to the leaf surface.
CONTROL — Whiteflies can’t survive cold winters, but overwinter on plants brought indoors and also on plants outside in southern zones with mild winters. Check everything you bring into your garden carefully. Also, check house plants before you bring them indoors in fall.
These tiny insects move through their life cycle so quickly that they can build up a devastating population in a matter of weeks. At each stage of life, they respond differently to controls. You can use yellow sticky traps to capture the adult whiteflies or knock the adults and larvae from the leaves with a strong stream of water. The larvae and eggs can also be rubbed from the leaves or use an insecticidal soap about once a week over several weeks to take care of them.