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Scirtothrips dorsalis

Scirtothrips dorsalis

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Encyclopedia
The chilli thripsThis is the more common international spelling of "chilli" outside of the United States. This spelling has been preserved in the common name for the insect by entomologists in the United States in deference to the body of literature already published for this species by international authors. or yellow tea thrips, Scirtothrips dorsalis Hood, is an extremely successful invasive species
Invasive species
"Invasive species", or invasive exotics, is a nomenclature term and categorization phrase used for flora and fauna, and for specific restoration-preservation processes in native habitats, with several definitions....

 of pest-thrips
Thrips
Thrips are tiny, slender insects with fringed wings . Other common names for thrips include thunderflies, thunderbugs, storm flies, thunderblights, and corn lice...

 which has expanded rapidly from Asia over the last twenty years, and is gradually achieving a global distribution. It has most recently been reported in St. Vincent (2004) Florida (2005), Texas (2006), and Puerto Rico (2007). It is a pest of economic significance with a broad host range, with prominent pest reports on crops including pepper
Chili pepper
Chili pepper is the fruit of plants from the genus Capsicum, members of the nightshade family, Solanaceae. The term in British English and in Australia, New Zealand, India, Malaysia and other Asian countries is just chilli without pepper.Chili peppers originated in the Americas...

, mango
Mango
The mango is a fleshy stone fruit belonging to the genus Mangifera, consisting of numerous tropical fruiting trees in the flowering plant family Anacardiaceae. The mango is native to India from where it spread all over the world. It is also the most cultivated fruit of the tropical world. While...

, citrus
Citrus
Citrus is a common term and genus of flowering plants in the rue family, Rutaceae. Citrus is believed to have originated in the part of Southeast Asia bordered by Northeastern India, Myanmar and the Yunnan province of China...

, strawberry
Strawberry
Fragaria is a genus of flowering plants in the rose family, Rosaceae, commonly known as strawberries for their edible fruits. Although it is commonly thought that strawberries get their name from straw being used as a mulch in cultivating the plants, the etymology of the word is uncertain. There...

, grapes, cotton
Cotton
Cotton is a soft, fluffy staple fiber that grows in a boll, or protective capsule, around the seeds of cotton plants of the genus Gossypium. The fiber is almost pure cellulose. The botanical purpose of cotton fiber is to aid in seed dispersal....

, tea
Tea
Tea is an aromatic beverage prepared by adding cured leaves of the Camellia sinensis plant to hot water. The term also refers to the plant itself. After water, tea is the most widely consumed beverage in the world...

, peanuts
Peanuts
Peanuts is a syndicated daily and Sunday American comic strip written and illustrated by Charles M. Schulz, which ran from October 2, 1950, to February 13, 2000, continuing in reruns afterward...

, blueberry
Blueberry
Blueberries are flowering plants of the genus Vaccinium with dark-blue berries and are perennial...

, and rose
Rose
A rose is a woody perennial of the genus Rosa, within the family Rosaceae. There are over 100 species. They form a group of erect shrubs, and climbing or trailing plants, with stems that are often armed with sharp prickles. Flowers are large and showy, in colours ranging from white through yellows...

s. Chilli thrips appear to feed preferentially on new growth, and infested plants usually develop characteristic wrinkled leaves, and a distinctive brown scarring along the veins of leaves, the buds of flowers, and the calyx of fruit. Feeding damage can reduce the sale value of crops produced, and in sufficient numbers, kill plants already aggravated by environmental stress. This thrips has also been implicated in the transmission of three tospoviruses, but there is some controversy over its efficiency as a vector.

This thrips has a rapid life cycle, and can develop from egg to adult in slightly less than two weeks under optimal weather conditions.

Identification


A rough field identification can be made of this thrips by searching for the following traits under low power magnification: small size (under a millimeter in length), yellow coloration, dark antennae, and dark striping on the lower abdomen.

It can be specifically identified and confirmed through the presence of forked sense cones on antennal segments III and IV, antennomeres I-II are pale and III to IX are dark; there are three discal setae on the lateral margins of abdominal tergites, with pronotal posteromarginal seta II nearly one and a half times the length of I or III, a complete posteromarginal comb on tergite VII; and three ocellar setae with III between posterior ocelli.

Recent research suggests that S. dorsalis may represent a species complex
Species complex
A species complex is a group of closely related species, where the exact demarcation between species is often unclear or cryptic owing to their recent and usually still incomplete reproductive isolation. Ring species, superspecies and cryptic species complex are example of species complex...

 of two or three disparate species
Species problem
The species problem or species concept is a mixture of difficult, related questions that often come up when biologists identify species and when they define the word "species"....

 who are morphologically similar.

Biology


Like all thrips of suborder Terebrantia, S. dorsalis undergoes two 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;...

al stages followed by two "false" 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...

l stages, and under optimal conditions, this thrips may reach adulthood in approximately two weeks. However, research has shown that the length of these life-history stages are flexible within a group depending on an individual’s access to nutrients and temperature. Nymphs entering the metamorphic process drop off of the plant during the first of two propual stages, and then complete their development in loose soil or leaf litter at the base of their host - but have been observed to pupate in any dark and humid crevice low on the plant, including bark and the folds of tightly packed lower leaves or flowers. The pupal process can range from two days to a full week. In temperate regions where the temperature falls below the critical lower threshold, non-diapausing adults are reported to overwinter in the soil or apical buds. Colder temperatures may even drive pupation, but this has not been experimentally confirmed.

Post-emergence
Imago
In biology, the imago is the last stage of development of an insect, after the last ecdysis of an incomplete metamorphosis, or after emergence from the pupa where the metamorphosis is complete...

, females have a pre-oviposition period of one to two days. Using their ovipositor, females lay single eggs within the plant tissue, and may lay an average of forty eggs during their lifetime. Females of S. dorsalis prefer to lay their eggs inside of young leaves and buds at the apical meristem of plants, but as populations increase, will lay their eggs within the surface of mature leaves. Depending on temperature, eggs may gestate for one to three weeks. After hatching, larvae will migrate from older leaves to the newer growth at terminals. Like many thrips, S. dorsalis appears to prefer feeding on new growth and young plants, and is often found on the newer top leaves on smaller plants, although individual plant morphology and chemistry may result in some distributional differences.

Nymph populations will continue to increase so long as new shoots are allowed to grow, and adults are permitted to land. Physically manipulating the host by removing preferred feeding sites has been shown to reduce thrips density on the plant, but also to increase the relative rate of between-plot dispersal.

History of Expansion


While it is currently believed that the point of biogeographical
Biogeography
Biogeography is the study of the distribution of species , organisms, and ecosystems in space and through geological time. Organisms and biological communities vary in a highly regular fashion along geographic gradients of latitude, elevation, isolation and habitat area...

 origin for the thrips is in Southeast Asia or on the Indian subcontinent, the original host is unknown. Chili peppers did not arrive in India until the sixteenth and seventeenth centuries with Portuguese traders, so the host upon which S. dorsalis was first described cannot be the point of origin. Given S. dorsalis’ broad polyphagy and long history of pestilent behavior, it has been speculated that a weed such as castor
Castor
Castor derives from the , meaning "beaver", or "he who excels". It originally referred to Castor, one of the Dioscuri/Gemini twins of Graeco-Roman mythology.Castor or CASTOR may also refer to:-Science and technology:...

 that was adopted for agriculture may have been one of several hosts of origin, and that the thrips adapted and began to exploit other hosts as they became available in the changing agricultural landscape.

It spread rapidly throughout the contiguous region of southeastern Asia fairly early, and there are many historical instances of this thrips attacking key crops on a regular basis. In India, it has been described as a pest of castor, pepper, cotton, tea, mango, and peanut. Outside of India, it has been reported as pest in China on tea and fruits like litchi, in Taiwan on citrus and vegetable, on citrus and tea in Japan, many vegetable and fruit crops in Thailand, peppers and mango in Vietnam, and even seasonally on the Korean peninsula.

Under the pressures of globalization
Globalization
Globalization refers to the increasingly global relationships of culture, people and economic activity. Most often, it refers to economics: the global distribution of the production of goods and services, through reduction of barriers to international trade such as tariffs, export fees, and import...

 and trade, this thrips has continued to expanded its range, and in 1997 EPPO
Eppo
Eppo may refer to:* Australian surfer Michael Eppelstun * European and Mediterranean Plant Protection Organization * ICAO code for Poznań-Ławica Airport* Eppo A Dutch comic magazine....

 recognized this pest as one with significant potential for global expansion. By that point it had already become fairly established beyond its precinctive range, had been intercepted at South African ports in 1986, noted as a pest in Kenya by 1997, and infesting cotton in Côte d'Ivoire by 1999. It has been described as a pest in Australia on cashew in 1998, and on strawberry and tea only a few years later.

It was only a matter of time before S. dorsalis was intercepted in the United States and the Caribbean region. While the thrips had been reported from port interceptions in Florida in 1995 and in Texas in 2000, surveys failed to detect any established populations or other sightings of the thrips. However, interceptions of this insect at a Miami port under the calyces of pepper from St. Vincent in 2003 inspired the USDA to act in order to predict and prevent the pest’s arrival. APHIS
Aphis
Aphis may refer to:* Aphis, a genus of aphid species* Animal and Plant Health Inspection Service , organizational unit of the USDA* HMS Aphis , Royal Navy insect class gunboat...

 and 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...

 responded with investigations of islands in the Caribbean. They found the pest already distributed throughout the Caribbean, and speculated that it had almost certainly already spread throughout South and Central America.

In late 2005, S. dorsalis was reported as a significant pest on Palm Beach County ornamental roses, and reports from other counties on the Knock Out cultivar of rose and pepper rapidly followed thereafter. By January 2007, the thrips had been found in more than thirty counties from Alachua to Monroe , and has been detected in southern Georgia. It has been spotted several times on retail roses in south Texas, and anecdotal evidence suggests that the expansion into Texas counties is probably underreported. Models of climatological and host potential suggest that this thrips has the potential to expand its range to cover much of the southeast, the gulf coast region, and the western seaboard.

Impact


The characteristic feeding damage of S. dorsalis was recognized as “Murda disease” on chili long before the thrips was associated with and then determined to be the cause of the blight. Prolonged feeding by thrips curls tender leaves and buds, and will turn fruits and flowers from bronze to black in color, rendering the plant material unmarketable. Even slightly damaged or scarred vegetables or inflorescences are often viewed as unmarketable, and these damaged commodities will fetch a lower price, reducing a grower's return on their investment. Insects feeding in new growth limits and stunts overall plant growth, and may induce abortion of fruit. When thrips feed in high enough densities, or in sufficiently dry climates, this process results in the eventual desiccation and death of their host plant. Even low densities of thrips can contribute to the decline in fruit production and plant health, especially during times of drought.

S. dorsalis has been implicated in the transmission of several separate tospoviruses, but recent experiments have cast some doubt on the efficiency at which S. dorsalis actually transmits the virus to its hosts. It may be a member of a class described in a near relative, Thrips palmi
Thrips palmi
Thrips palmi is an insect from the Thrips genus .It is a primary vector of plant viruses. Also known as the melon thrips, T...

Karny: an infected non-transmitter with detectable levels of virus.

External links

  • fact site from Texas A&M
    Texas A&M University
    Texas A&M University is a coeducational public research university located in College Station, Texas . It is the flagship institution of the Texas A&M University System. The sixth-largest university in the United States, A&M's enrollment for Fall 2011 was over 50,000 for the first time in school...

  • fact site from 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...

  • provisional management guidelines, provided by 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...

  • Description and images, provided by PaDIL
  • Taxonomic literature and synonymy for the species, provided by CSIRO
  • More images
  • 2006 New Pest advisory, provided by APHIS
    Aphis
    Aphis may refer to:* Aphis, a genus of aphid species* Animal and Plant Health Inspection Service , organizational unit of the USDA* HMS Aphis , Royal Navy insect class gunboat...

  • chilli thrips on the UF
    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...

     / IFAS
    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 Web site
  • Species Profile- Chilli Thrips (Scirtothrips dorsalis), National Invasive Species Information Center, United States National Agricultural Library
    United States National Agricultural Library
    The United States National Agricultural Library is one of the world's largest agricultural research libraries, and serves as a National Library of the United States and as the library of the United States Department of Agriculture...

    . Lists general information and resources for Chilli Thrips.
  • CERIS map of county records in the United States