Whiteflies are one of those garden pests that can suddenly appear out of nowhere and result in an infestation, even on indoor plants.
It’s easy to identify whiteflies because whenever you water or move your plants a tiny snowstorm of the insects will appear. It looks like your plant has really bad dandruff. At the first sign of them, take action because they multiply quickly! The flies are very tiny, less than 1/8-inch long, so the only way to really see them is with a magnifying glass or by looking for the white flurry when you move your plants.
As far as damage, whiteflies are along the lines of aphids. Both adult whiteflies and nymphs suck sap out of plants, rendering them weak or diseased. Although there really are two classes of whiteflies (one that feeds on outdoor plants and another that finds host plants in greenhouses), treatment for the pests is the same.
Beneficial insect predators of whiteflies include ladybugs, green lacewing and certain songbirds. Attract these good guys to your garden and they can help take care of your whitefly problem. From an companion plant perspective, marigolds and nasturtiums tend to repel whiteflies. Insecticidal soap and seaweed powder sprays both work when sprayed directly on the plant.