Whitefly

Lore & Background

Whiteflies are classified in the family Aleyrodidae, which comprises the entire superfamily Aleyrodoidea, related to the Psylloidea. The family appears in older literature as 'Aleurodidae', but that is a junior synonym. Most species have a wingspan under 3 mm and body length of 1–2 mm, though some 'giant whitefly' species exceed 5 mm. Sexual dimorphism occurs, with one sex markedly larger; in some giant tropical species, males are much larger than females. Adult Aleyrodidae have well-developed, seven-segmented antennae and two ocelli at the anterior margins of the compound eyes. The compound eyes often have a constriction between upper and lower halves, and in some species are completely separated—a feature used to distinguish genera such as Bemisia and Trialeurodes. Both sexes have functional mouthparts and two pairs of membranous wings; wing venation is reduced, often with only one unbranched vein per wing. Many species are covered with fine wax powder, giving a floury appearance, though not all are white—for example, Aleurocanthus woglumi is slaty black. The legs are well developed but not adapted to leaping. The digestive system includes a filter chamber, and all active stages produce honeydew, expelled through a vasiform orifice on the dorsal abdomen, which is taxonomically diagnostic.

Reader's Guide

Whiteflies are significant primarily as agricultural pests. In warm or tropical climates and greenhouses, they cause major crop protection problems, with worldwide economic losses estimated at hundreds of millions of dollars annually. Prominent pest species include Aleurocanthus woglumi (citrus blackfly), Aleyrodes proletella (cabbage whitefly), Bemisia tabaci (silverleaf whitefly), and Trialeurodes vaporariorum (greenhouse whitefly). While sap feeding can cause losses, the major harm is indirect: they secrete honeydew that supports sooty mold, inject saliva that may damage plants, and most importantly, transmit plant viruses. The most prominent disease vectors are in the genus Bemisia, transmitting Begomoviruses such as African cassava mosaic, bean golden mosaic, tomato yellow leaf curl, and others. The spread of biotypes like B. tabaci biotype B (also known as B. argentifolii) and biotype Q continues to cause severe crop losses, demanding increased pesticide use. Efforts to develop environmentally friendly integrated pest management systems are ongoing. The oldest whitefly fossils belong to the Mesozoic subfamily Bernaeinae, with the oldest representatives of extant subfamilies appearing in the Lower Cretaceous.

Did You Know?

• More than 1550 whitefly species have been described.
• Some giant whitefly species exceed 5 mm in size, and in some tropical species the males are much larger than the females.
• The compound eyes of some whitefly species have a complete separation between upper and lower halves, used to distinguish genera like Bemisia and Trialeurodes.