Host plants and damage
Whiteflies, especially the sweet potato whitefly Bemisia tabaci and the silver-leaf whitefly B. argentifolii, are polyphagous pests of the tropical and sub-tropical zones. They cause damage to many species of greenhouse vegetables, ornamentals, field crops and fruit trees. The whiteflies damage crops by extracting large quantities of phloem sap. The honeydew excreted by these insects serves as a substrate for sooty mould fungi that discolor parts of the plants used for food and fiber. In addition, many whitefly species serve as vectors of several economically important viral plant diseases. One of the most important ones is the Tomato Yellow Leaf Curl Virus (TYLCV) transmitted by the sweet potato whitefly and the silver-leaf whitefly. This disease hinders implementation of IPM/Biocontrol programs, especially in greenhouse tomatoes, due to the demand for zero tolerance for the level of this pest.

Morphology and biology
The adults are minute insects, measuring 0.85-1.2 mm in length with a wingspan of 1.8-3.0 mm. The wings and body are covered with fine wax particles, hence the name "whitefly". Eggs are deposited singly or in clusters, sometimes in an arc or circle, on the lower surface of leaves usually in young plant growth. The eggs are ovoid and possess a stalk (pedicel) which is inserted into the leaf surface and holds the egg in an erect position. In addition to serving as a means of attachment to the leaf, the stalk absorbs water from the plant into the egg. Fecundity of the two species of whiteflies varies between a few dozen to several hundred eggs, depending upon ambient temperature and host plant.

         egg patch of Bemisia tabaci
           

Following completion of embryonic development, the egg cracks and a crawler (first-instar nymph) hatches.
It has six functional legs and a pair of antennae. It walks rather quickly over the leaf surface in search of an available minor vein, then settles down, inserting its mouthparts into the phloem tissue, and begins extracting sap. The legs of the crawler degenerate and it remains sessile until it reaches the adult stage. 
Second- and third-instar whitefly nymphs have an oval body, transparent-yellow in color. In the fourth nymphal instar, commonly referred to as a "pupa", the red eyes and white wings of the adult are already visible. After adult eclosion, a typical T-shaped shaped slit is left in the empty integument of the pupa. Development time of the whitefly from egg to adult is ca. 21 days at a temperature of 28°C.