Dealing with a garden and houseplant pest Adult whiteflies are about 1/16 inch long. They feed on cucumbers, beans, tomatoes. and potatoes, as well as on many kinds of houseplants and ornamentals including azaleas, fuchsias, and chrysanthemums.
If, when you touch a plant, a cloud of tiny powdery whiteflies appears, it’s a sign of a serious infestation. Immature whiteflies suck juices from the undersides of leaves, causing them to yellow. wither, and finally drop off. Like aphids, whiteflies secrete a clear sticky substance (honeydew)which attracts ants and usually causes a black fungus (sooty mold).
At certain stages of their development, whiteflies are unaffected by pesticides. When you see flying adults in early summer, spray with malathion twice a week for 3 to 4 weeks.