Bemisia tabaci has been reported from all continents except Antarctica. Over 900 host plants have been recorded for B. tabaci and it reportedly transmits 111 virus species.
It is believed that B. tabaci has been spread throughout the world through the transport of plant products that were infested with whiteflies.
Once established, B. tabaci quickly spreads and through its feeding habits and the transmission of diseases, it causes destruction to crops around the world. B. tabaci is believed to be a species complex, with a number of recognised biotypes and two described extant cryptic species.
Description:
Eggs, deposited on the underside of leaves, (Note: circular egg deposition for Bemisia is rare) are tiny, oval-shaped, about 0.25mm in diameter and stand vertically on the leaf surface. Newly laid eggs are white then turn brownish.
Upon hatching the first instar nymph (0.3mm in length), commonly called the “crawler”, moves about the leaf in search of a place to insert its needle-like mouthparts into the plant to suck up plant phloem.
When the crawler finds this site, it malts to the second instar; its legs are pulled up under its body and the rest of the immature stage is sessile.
There are three additional nymphal instars (0.4-0.8mm) with the successive stage malting to a slightly larger form. The last nymphal instar develops red eye spots and is commonly called the “redeyed nymph.” This stage is often incorrectly called the pupal stage; incorrect because insects in this order Hemiptera have incomplete metamorphosis, thus there is no pupa.
Throughout the nymphal stages, the body of the whitefly is opaque white in colour and is covered by a waxy exoskeleton. As nymphs feed, they excrete large quantities of liquid waste in the form of honeydew.
Honeydew is rich in plant carbohydrates and as whiteflies feed and excrete, this waste is distributed onto plant leaves, flowers and fruit and supports the growth of sooty mould fungus, causing the plant to turn black.
Adult whitefly are about 1mm long with two pairs of white wings and light yellow bodies. Their bodies are covered with a waxy powdery material. While whitefly adults can be seen on all plant surfaces, they spend most of their time feeding, mating and ovi positing on the under surfaces of leaves.
Males and females are present, typically in even ratios, and mating takes place after an elaborate courtship period. Whiteflies have an interesting biology (called arrhenotoky) in which females can lay eggs that have not been fertilised and these eggs will result in male offspring.
Fertilised eggs will result in female offspring. Each female can produce as many as 200 eggs in her lifetime.. It takes 30-40 days to develop from egg to adult, depending on the temperature (OISAT, 2004).
The EPPO (2004) states that, “Infested plants may exhibit a range of symptoms due to direct feeding damage, contamination with honeydew and associated sooty moulds, whitefly-transmitted viruses and phytotoxic responses. There may be one, or a combination of the following symptoms:
chlorotic spotting, vein yellowing, intervein yellowing, leaf yellowing, yellow blotching of leaves, yellow mosaic of leaves, leaf curling, leaf crumpling, leaf vein thickening, leaf enations, leaf cupping, stem twisting, plant stunting, wilting and leaf loss. Phytotoxic responses such as a severe silvering of courgette and melon leaves usually indicate the presence of a Bernisia argentifolii infestation.”
Similar Species:
Trialeurodes vaporariorum
More
Occurs in:
agricultural areas, urban areas
Habitat description:
The EPPO (2004) states that, “Bemisia tabaci are usually detected by close examination of the undersides of leaves, which will reveal adults and/or nymphs. Shaking the plant may disturb the small white adults, which flutter out and quickly resettle. Adults may also be found on sticky traps placed above infested plants.”
Information Sourced From:
