Whiteflies are very small insects that resemble tiny white moths. Whiteflies usually feed on the lower surface of their host plant leaves. Whiteflies differ from most insects in the way they mate (side by side) and that their eggs absorb water from the host leaf after the eggs are inserted into the lower surface. From the egg hatches a minute crawler stage that moves about the leaf until it inserts its microscopic, threadlike mouthparts to feed by sucking sap from the phloem. Adults and nymphs excrete honeydew, a sticky, viscous liquid in which dark sooty molds grow. Because many species of adult whiteflies are similar in appearance, entomologists use the last nymph stage for specific identification. In 1986, a whitefly very similar to the sweetpotato whitefly suddenly became a noticeable pest of poinsettias and commercial vegetables in Florida and California. This whitefly spread throughout the greenhouse industry in the United States in the next few years and is now the most frequently encountered whitefly pest of poinsettia and gerbera daisy. In 1994, Bellows and Perring described this whitefly as a new species, the silverleaf whitefly. The silverleaf whitefly causes the leaves of melons and stems of poinsettias to blanch noticeably when these whiteflies are abundant.
