Whiteflies

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Rank & Taxon

Family Aleyrodidae

Description

Whiteflies are not true flies but are closely related to scales, mealybugs, and aphids. Adult whiteflies are usually around 2-3 mm long. They are tiny, soft-bodied insects that resemble very small moths. Color of the insect inself varies, but they are covered with a white waxy secretion that nearly always contributes largely to the appearance of the insect, regardless of the life stage. Eggs are usually attached to the underside of the leaf with a small pedicel and are frequently laid in arcs or circles accompanied by a dusting of white wax. All stages of nymphs superficially resemble scale insects and may have ornate waxy secretions in the later instars. The first instar, or crawler, has functional legs, while subsequent instars are sessile. The fourth instar, or pupa, is 0.5-2 mm in length, oval or elongate-oval in length, with a body margin that is either smooth or variously sculpted. The pupa is generally the stage that is used to make species identifications, using the arrangement of pores and other minute structures that must be examined microscopically on mounted specimens. 

Distribution

Worldwide, though occur infrequently in cooler temperate regions; 2 subfamilies, 130 genera, representing around 1,450 described species

Biology/Life cycle

Whiteflies pass through four instars on their way from egg to adult. Whitefly reproduction is usually sexual, with fertilized eggs producing females and unfertilized eggs producing males. Eggs are usually laid on the underside of leaves in circles or arcs and are frequently conspicuous due to a dusting of white wax. The first instar, or crawler stage, emerges and attaches to the plant to begin feeding. The nymphs become immobile after their first molt, and may closely resemble scale insects in the next few stages. The fourth instar is commonly referred to as a "pupa" though it is not a true pupa. Feeding ceases during this stage, and the insect emerges as the winged adult. Phloem sap is the primary food source for whiteflies at all stages. Most pest species of whitefly have several to many generations per year, but some species are thought to have only one or two generations per year.

Hosts

Palms: primarily Cocos nucifera (coconut palm), but can also occur on other palm species including Washingtonia spp. (fan palms), Phoenix dactylifera (date palm), Veitchia merrillii (Christmas palm), and Elaeis guineensis (African oil palm)

Other: can infest a wide variety of dicotyledonous plants and are likely primarily adapted to them

Representative taxa on palms

Aleurodicus dispersus (spiraling whitefly) is commonly found on coconut palms in areas where they both occur, though it is not always considered a pest.

Aleurotrachelus atratus is found throughout the Caribbean, northern South America, and southern Florida, and infests various palm species, including coconut palm, African oil palm, and Christmas palm.

May be confused with

Some whitefly pupae can look very similar to palm aphids (Cerataphis spp.).

Additional comments

All feeding stages of whiteflies secrete honeydew and so may be accompanied by sooty mold, which flourishes on the honeydew. However, few species of whitefly are ant tended. Identification of whitefly species is usually based on the morphology of the fourth instar ("pupa") and requires mounting of specimens onto microscope slides. For definitive species confirmation, specimens should be submitted to an expert.

Some whitefly pupae can look very similar to palm aphids (Cerataphis spp.).

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October 8, 2010
Lucid CentralSouthern Plant Diagnostic NetworkUniversity of Florida ExtensionPPQAPHISUSDA