Control of these insects should be directed at the undersurface of the leaves. Many of the whiteflies are believed to have originated from tropical regions of the world. This group has a complex life cycle and metamorphosis - if you are interested, consult a general entomology text for further information. Whiteflies can become extremely troublesome in the greenhouse where conditions may be optimum for their growth, reproduction, and survival. They are common problems on many floral crops and can cause extensive damage to the plant, as well as produce honeydew which may lead to sooty mold.
Some whiteflies also are important as vectors of some plant pathogens.
Whiteflies can be extremely difficult to kill with some insecticides due to the development of resistance in the populations. Unless controlled, these insects may completely destroy the commercial value of floricultural crops. Adults are usually found on the undersurface of the leaf, and new crawlers move about on the plant. Once they insert their mouthparts to feed, they never move again until they mature. In 1986, a whitefly similar to the sweetpotato whitefly suddenly became a noticeable pest of poinsettias and other plants in Florida and California.