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.
