Bemisia tabaci is a species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 of whitefly

Whitefly

The whiteflies, comprising only the family Aleyrodidae, are small hemipterans. More than 1550 species have been described. Whiteflies typically feed on the underside of plant leaves.-Agricultural threat:...

 found around the world and probably native to India

India

India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...

.

Common names

• mosca branca (Brazil)
• cotton whitefly (English),
• mosca blanca (Dominican Republic),
• sweet potato whitefly (English),
• yellow vein mosaic of okra/bhindi (India),
• Tabakmottenschildlaus (German)

Distribution

The European and Mediterranean Plant Protection Organization

European and Mediterranean Plant Protection Organization

The European and Mediterranean Plant Protection Organization is an intergovernmental organisation responsible for European cooperation in plant protection in the European and Mediterranean region...

 ("EPPO") (2004) reports that B. tabaci may have originated in India, but the evidence is not conclusive.

The insects are self-propelled over local distances. Bernays (1999) states that, "Winged adults fly about, however, and move between crops.

Bemisia tabaci is reported from all continents except Antarctica The Pacific Islands Pest List Database shows the distribution of the whitefly in the Pacific region. It is reported in the Cook Islands

Cook Islands

The Cook Islands is a self-governing parliamentary democracy in the South Pacific Ocean in free association with New Zealand...

, Fiji

Fiji

Fiji , officially the Republic of Fiji , is an island nation in Melanesia in the South Pacific Ocean about northeast of New Zealand's North Island...

 Islands; Palau

Palau

Palau , officially the Republic of Palau , is an island nation in the Pacific Ocean, east of the Philippines and south of Tokyo. In 1978, after three decades as being part of the United Nations trusteeship, Palau chose independence instead of becoming part of the Federated States of Micronesia, a...

, Papua New Guinea

Papua New Guinea

Papua New Guinea , officially the Independent State of Papua New Guinea, is a country in Oceania, occupying the eastern half of the island of New Guinea and numerous offshore islands...

, Samoa

Samoa

Samoa , officially the Independent State of Samoa, formerly known as Western Samoa is a country encompassing the western part of the Samoan Islands in the South Pacific Ocean. It became independent from New Zealand in 1962. The two main islands of Samoa are Upolu and one of the biggest islands in...

, French Polynesia

French Polynesia

French Polynesia is an overseas country of the French Republic . It is made up of several groups of Polynesian islands, the most famous island being Tahiti in the Society Islands group, which is also the most populous island and the seat of the capital of the territory...

, The Federated States of Micronesia, Vanuatu

Vanuatu

Vanuatu , officially the Republic of Vanuatu , is an island nation located in the South Pacific Ocean. The archipelago, which is of volcanic origin, is some east of northern Australia, northeast of New Caledonia, west of Fiji, and southeast of the Solomon Islands, near New Guinea.Vanuatu was...

, New Caledonia

New Caledonia

New Caledonia is a special collectivity of France located in the southwest Pacific Ocean, east of Australia and about from Metropolitan France. The archipelago, part of the Melanesia subregion, includes the main island of Grande Terre, the Loyalty Islands, the Belep archipelago, the Isle of...

, Niue

Niue

Niue , is an island country in the South Pacific Ocean. It is commonly known as the "Rock of Polynesia", and inhabitants of the island call it "the Rock" for short. Niue is northeast of New Zealand in a triangle between Tonga to the southwest, the Samoas to the northwest, and the Cook Islands to...

 and Kiribati

Kiribati

Kiribati , officially the Republic of Kiribati, is an island nation located in the central tropical Pacific Ocean. The permanent population exceeds just over 100,000 , and is composed of 32 atolls and one raised coral island, dispersed over 3.5 million square kilometres, straddling the...

.

Over 900 host plants are recorded for B. tabaci and it reportedly transmits 111 virus

Virus

A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...

 species. It is believed that B. tabaci has been spread throughout the world through the transport of plant products infested with whiteflies. Once established, B. tabaci quickly spreads and through its feeding habits and the transmission of the diseases it carries, it causes destruction to crops around the world. Bemisia tabaci is believed to be a species complex, with a number of recognized 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 0.25 mm (0.01 inches) in diameter, and stand vertically on the leaf surface. Newly laid eggs are white then turn brownish. Upon hatching the first instar nymph

Nymph

A nymph in Greek mythology is a female minor nature deity typically associated with a particular location or landform. Different from gods, nymphs are generally regarded as divine spirits who animate nature, and are usually depicted as beautiful, young nubile maidens who love to dance and sing;...

 (0.3mm in length), commonly called the “crawler”, moves about the leaf in search for a place to insert its needle-like mouthparts into the plant to suck up plant phloem. When the crawler finds this site, it molts 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 or 0.016-0.032 inches) with the successive stage molting to a slightly larger form. The last nymphal instar develops red eye spots, and is commonly called the “red-eyed nymph.” This stage often is incorrectly called the pupal stage; incorrect because insects in this order (Hemiptera

Hemiptera

Hemiptera is an order of insects most often known as the true bugs , comprising around 50,000–80,000 species of cicadas, aphids, planthoppers, leafhoppers, shield bugs, and others...

) have incomplete metamorphosis, thus there is no pupa

Pupa

A pupa is the life stage of some insects undergoing transformation. The pupal stage is found only in holometabolous insects, those that undergo a complete metamorphosis, going through four life stages; embryo, larva, pupa and imago...

. Throughout the nymphal stages, the body of the whitefly is opaque white in color, and is covered by a waxy exoskeleton. As nymphs feed, they excreted 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 on plant leaves/flowers/ and fruit and supports the growth of sooty mold fungus, causing the plant to turn black. Adult whiteflies are about 1mm (0.04 inches) long with two pairs of white wings and light yellow bodies. Their bodies are covered with waxy powdery materials. While whitefly adults can be seen on all plant surfaces, they spend most of their time feeding, mating, and ovipositing 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 fertilized and these eggs will result in male offspring. Fertilized 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 B. argentifolii infestation."

Habitat description

The sweet potato whitefly occurs in both urban and agricultural areas.

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."

General impacts

Six hundred host plants have been cited. Bemisia tabaci possibly originated in India and as a result of widespread dispersal, particularly during the last 15 years, is now distributed nearly worldwide. Bemisia tabaci is also a vector of over 100 plant viruses in the general Begomovirus

Begomovirus

The genus Begomovirus contains more than 200 species and belongs to the taxonomic family Geminiviridae. They are plant viruses that as a group have a very wide host range, infecting dicotyledonous plants...

 (Geminiviridae

Geminiviridae

Geminiviruses are plant viruses which have single-stranded circular DNA genomes encoding genes that diverge in both directions from a virion strand origin of replication . According to the Baltimore classification they are considered class II viruses...

), Crinivirus

Crinivirus

Crinivirus is a genus of plant viruses that belong to the family Closteroviridae. They are also known as the lettuce infectious yellows virus group...

 (Closteroviridae

Closteroviridae

The Closteroviridae are a family of viruses plant viruses with filamentous, helically constructed particles showing distinct cross-banding and varying in length from 650 nanometers to over 2000 nm. The genome is a single strand of positive sense RNA whose size varies from 13 - 19...

) and Carlavirus

Carlavirus

Carlavirus, also known as "Carnation latent virus group" is a genus of virus that infects plants. It contains thirty-five described species and twenty-nine tentative species..-Virology:...

 or Ipomovirus (Potyviridae

Potyviridae

The Potyviridae are a family of plant viruses. They are . Their genome is composed of positive-sense RNA which is surrounded by a protein coat made up of a single viral encoded protein called a capsid. All induce the formation of virus inclusion bodies called in their hosts...

).Jones, 2003

Damage is caused not only by direct feeding, but also through transmission of viruses. Begomoviruses are the most numerous of the B. tabaci transmitted viruses and can cause crop yield losses of between 20% and 100%. The EPPO (2004) states that

"Since the early 1980s, B. tabaci has caused escalating problems to both field and protected agricultural crops and ornamental plants. Heavy infestations of B. tabaci and B. argentifolii may reduce host vigour and growth, cause chlorosis and uneven ripening, and induce physiological disorders. The larvae produce honeydew on which sooty moulds grow, reducing the photosynthetic capabilities of the plant, resulting in defoliation and stunting. B. tabaci is known to be a potentially damaging pest of crops such as cotton, brassicas, cucurbits, okra, solanums in the tropics and subtropics".

Ellsworth and Martinez-Carrillo (2001) state that

"Bemisia tabaci’s small size belies its ability to move relatively large distances locally, placing many hosts within communities at risk of infestation. This ability to disperse is made worse by its extensive movement through commerce of plant products around the globe. The small size and rapid reproductive potential are other characteristics that result in explosive population growth. The damage potential of this pest as a direct plant stressor, virus vector, and quality reducer (e.g., by contamination with excreta) is substantial. These attributes, among others, render this species a shared pest within agricultural communities."

Cassava mosaic disease (CMD) and cassava mosaic geminiviruses (CMGs) are transmitted by the whitefly destroying cassava crops. Cassava (Manihot esculenta) is one of the most widely grown staple food crops in sub-Saharan Africa

Africa

Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...

. It is particularly important to the poorest farmers because of its role in food security and as a source of income. Agriculture in tropical and subtropical regions are most threatened, with crops such as bean

Bean

Bean is a common name for large plant seeds of several genera of the family Fabaceae used for human food or animal feed....

s, cucurbit

Cucurbitaceae

The plant family Cucurbitaceae consists of various squashes, melons, and gourds, including crops such as cucumber, pumpkins, luffas, and watermelons...

s, pepper

Pepper

- Plants and plant products :The genus Piper of the pepper family , including for example:* Black pepper, white and green pepper, Piper nigrum* Cubeb, Piper cubeba, also known as Java pepper* Long pepper, Piper longum...

s, cassava

Cassava

Cassava , also called yuca or manioc, a woody shrub of the Euphorbiaceae native to South America, is extensively cultivated as an annual crop in tropical and subtropical regions for its edible starchy tuberous root, a major source of carbohydrates...

s and tomato

Tomato

The word "tomato" may refer to the plant or the edible, typically red, fruit which it bears. Originating in South America, the tomato was spread around the world following the Spanish colonization of the Americas, and its many varieties are now widely grown, often in greenhouses in cooler...

es particularly being affected. Tomato yellow leaf curl virus

Tomato yellow leaf curl virus

Tomato yellow leaf curl virus is a plant pathogenic virus of the family Geminiviridae.-External links:***...

 (TYLCV) limits tomato production in several geographic regions, including the Middle East

Middle East

The Middle East is a region that encompasses Western Asia and Northern Africa. It is often used as a synonym for Near East, in opposition to Far East...

 and the Far East

Far East

The Far East is an English term mostly describing East Asia and Southeast Asia, with South Asia sometimes also included for economic and cultural reasons.The term came into use in European geopolitical discourse in the 19th century,...

.

Uses

Considerable research has been done on the taxonomy of B. tabaci, and Perring (2001) proposed seven distinct groups within the complex. B. tabaci is believed to be a species complex, with a number of recognized biotypes and two described extant cryptic species. Nineteen biotypes have been identified based on non-specific esterase banding patterns (biotypes A-T), and the two described species are B. tabaci and Bemisia argentifolii Bellows and Perring. B. argentifolii carries the common name of silverleaf whitefly

Silverleaf whitefly

The silverleaf whitefly is one of several whiteflies that are currently important agricultural pests. The Silverleaf Whitefly is classified in the family Aleyrodidae, and is included in the large sub-order of insects, Heteroptera...

.

Invasion pathways to new locations

The United Kingdom

United Kingdom

The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

 Department for Environment, Food and Rural Affairs

Department for Environment, Food and Rural Affairs

The Department for Environment, Food and Rural Affairs is the government department responsible for environmental protection, food production and standards, agriculture, fisheries and rural communities in the United Kingdom...

 (2001) states that,

"Ornamental plants are the main source of introduction of B. tabaci to the UK. B. tabaci was first intercepted in the UK in 1987 on poinsettia cuttings and since then outbreaks have occurred annually, again mainly on poinsettia. It has also been intercepted on a wide range of other plant material including bedding plants such as Lantana and Verbena on finished pot plants such as Ficus species, ornamental citrus, and also on herb cuttings."

Management information

The Whitefly IPM Project provides a paradigm for future work on cassava mosaic begemoviruses and whiteflies on cassava in both Africa and elsewhere. Ellsworth and Martinez-Carrillo (2001) offer an extensive integrated management approach. The report details the exact plans and steps that are necessary to adopt and follow through with the integrated pest management guidelines suggested. A summary of the guidelines sketches out the steps to be taken.

For details on preventative measures, chemical, physical, cultural and biological control options, please see management information.

Lifecycle stages

McAuslane (2000) outlines the life cycle of B. tabaci stating that,

"Bemisia tabaci eggs are oval in shape and somewhat tapered towards the distal end. The egg is pearly white when first laid but darkens over time. At 25 °C, the eggs will hatch in six to seven days. The first nymphal instar is capable of limited movement and is called the crawler. The dorsal surface of the crawler is convex while the ventral surface, appressed to the leaf surface, is flat. The crawlers usually move only a few centimeters in search of a feeding site but can move to another leaf on the same plant. After they have begun feeding, they will molt to the second nymphal instar, usually two to three days after eclosion from the egg. The second, third and fourth nymphal instars are immobile with atrophied legs and antennae, and small eyes. The nymphs secrete a waxy material at the margins of their body that helps adhere them to the leaf surface. The second and third nymphal instars each last about two to three days. The red-eyed nymphal stage is sometimes called the 'pupal stage'. There is no molt between the fourth nymphal instar and the red-eyed nymphal stage but there are morphological differences. The fourth and red-eyed nymphal stages combined lasts for five to six days. The stage gets its name from the prominent red eyes that are much larger than the eyes of earlier nymphal instars." Adult females insert their eggs into the foliage of host plants and the newly-hatched nymphs settle for larval life with little movement on the plant chosen by the parent. Winged adults fly about, however, and move between crops ( Byrne et al.. 1996). Individual females often feed on a variety of different plants, including crops and weeds within crops ( Byrne et al. 1990). The species of plants fed upon differ in quality, and while some plant species are best for survival, others are better for egg production ( Costa et al. 1991). Adults live for a week or more ( Byrne & Bellows 1991) and much of the egg production depends on the food ingested during adulthood."

This species has been nominated as among 100 of the "World's Worst" invaders.

External links

• Sweetpotato whitefly B biotype or silverleaf whitefly on the University of Florida
  University of Florida
  The University of Florida is an American public land-grant, sea-grant, and space-grant research university located on a campus in Gainesville, Florida. The university traces its historical origins to 1853, and has operated continuously on its present Gainesville campus since September 1906...
  
   / Institute of Food and Agricultural Sciences
  Institute of Food and Agricultural Sciences
  The University of Florida’s Institute of Food and Agricultural Sciences is a federal-state-county partnership dedicated to developing knowledge in agriculture, human and natural resources, and the life sciences, and enhancing and sustaining the quality of human life by making that information...
  
  Featured Creatures website
• USDA Whitefly Knowledgebase