Scirtothrips dorsalis | |
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Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Arthropoda |
Class: | Insecta |
Order: | Thysanoptera |
Family: | Thripidae |
Genus: | Scirtothrips |
Species: | S. dorsalis |
Binomial name | |
Scirtothrips dorsalis Hood, 1919 | |
Synonyms | |
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Scirtothrips dorsalis, the chilli thrips [derivation 1] or yellow tea thrips, is an extremely successful invasive species of pest-thrips [1] 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, eggplant, [2] mango, citrus, strawberry, grapes, cotton, tea, peanuts, blueberry, and roses. [3] Chilli thrips appear to feed preferentially on new growth, and infested plants usually develop characteristic wrinkled leaves, with 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. [4]
This thrips has a rapid life cycle, and can develop from egg to adult in slightly less than two weeks under optimal weather conditions.
A tentative (but inconclusive) 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. [5] [6] [7]
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. [5] [8] [9]
Recent research concludes that S. dorsalis does represent a species complex of three or more disparate species who are morphologically similar but genetically distinct. [10] [11]
Like all thrips of suborder Terebrantia, S. dorsalis undergoes two nymphal stages followed by two "false" pupal stages, [12] and under optimal conditions, this thrips may reach adulthood in approximately two weeks. [13] 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 [14] and temperature. [13] 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 [15] or flowers. The pupal process can range from two days to a full week. [13] 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. [16] [17] [18] Colder temperatures may even drive pupation, but this has not been experimentally confirmed.
Post-emergence, females have a pre-oviposition period of one to two days. [13] Using their ovipositor, females lay single eggs within the plant tissue, [19] and may lay an average of forty eggs during their lifetime. [13] 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. [12] [20] Depending on temperature, eggs may gestate for one to three weeks. [13] After hatching, larvae will migrate from older leaves to the newer growth at terminals. [21] Like many thrips, S. dorsalis appears to prefer feeding on new growth and young plants, [7] [12] [16] and is often found on the newer top leaves on smaller plants, although individual plant morphology and chemistry may result in some distributional differences. [16]
Nymph populations will continue to increase so long as new shoots are allowed to grow, [22] and adults are permitted to land. [23] 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. [22] [24]
Molecular evidence currently suggests that the point of biogeographical origin for the thrips is in Southeast Asia or on the Indian subcontinent, [11] but the original host remains unknown. Chili peppers did not arrive in India until the sixteenth and seventeenth centuries with Portuguese traders, [25] 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 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.[ citation needed ]
It spread rapidly throughout the contiguous region of southeastern Asia fairly early, and there are many historical instances of these thrips attacking key crops on a regular basis. In India, it has been described as a pest of castor, [20] pepper, [26] cotton, [27] tea, [12] [28] mango, and peanut. [29] Outside of India, it has been reported as pest in China on tea and fruits like litchi, [30] in Taiwan on citrus and vegetable, [31] on citrus and tea in Japan, [18] [32] many vegetable and fruit crops in Thailand, [33] peppers and mango in Vietnam, and even seasonally on the Korean peninsula. [34]
Under the pressures of globalization and trade, this thrips has continued to expand its range, [1] and in 1997 EPPO [35] 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, [36] noted as a pest in Kenya by 1997, [37] and infesting cotton in Côte d'Ivoire by 1999. [38] It has been described as a pest in Australia on cashew in 1998, [39] and on strawberry and tea only a few years later. [9] [40]
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. [41] [42] However, interceptions of this insect at a Miami port under the calyces of pepper from St. Vincent in 2003 [41] inspired the USDA to act in order to predict and prevent the pest's arrival. [43] APHIS and the University of Florida responded with investigations of islands in the Caribbean. [6] [7] They found the pest already distributed throughout the Caribbean, and speculated that it had almost certainly already spread throughout South and Central America. [44]
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. [42] By January 2007, the thrips had been found in more than thirty counties from Alachua to Monroe, and has been detected in southern Georgia. [45] 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. [46] [47]
The characteristic feeding damage of S. dorsalis was recognized as "Murda disease" [48] [49] 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. [37] 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. [50] [51]
S. dorsalis has been implicated in the transmission of several separate tospoviruses, [4] 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 Karny: an infected non-transmitter with detectable levels of virus. [52]
Chilli thrips are known to develop resistance to pesticides extremely quickly [ citation needed ]. This is thought to be a consequence of the short timespan and large capacity of their reproductive cycle, drawing comparisons to spider mites. In addition, they have an extremely wide host range, providing population reservoirs even after the most thorough pesticide application.
Only the insecticides spinosyn and abamectin are known to be effective against this pest[ citation needed ]. Neem based products are considered effective synergists[ citation needed ]. Product rotation is integral to resistance prevention programs. Insecticidal soaps and horticultural oils are both effective, but only in very frequent, sometimes impractical spray schedules (at least once a week)[ citation needed ]. Systemic neonicotinoids such as imidacloprid were once considered to be sparing of beneficial insects and natural predators, and recommended for integrated pest management of chilli thrips, especially when used as a soil soak or drip irrigation product[ citation needed ]. The past decade has revealed that neonicotinoids can seriously impact beneficial insects, especially bees, through effects that are not immediately apparent - even at trace concentrations[ citation needed ].
Entomopathogenic fungi are an emerging control method being used against a variety of insects, including chilli thrips[ citation needed ]. Beauveria bassiana and Metarhizium spp. have both attracted research for this use. Multiple such products are available for use in Asian countries[ citation needed ]. Only one Beauveria bassiana product is registered as an insecticide in the United States. Tests of these products show that they are mediocre control agents, but may be useful in rotation with other insecticides or in combination with spray oils[ citation needed ]. Unfortunately, these agents are broad spectrum insecticides, and do not spare natural predators or desirable insects such as bees and butterflies.
Thrips are minute, slender insects with fringed wings and unique asymmetrical mouthparts. Entomologists have described approximately 7,700 species. They fly only weakly and their feathery wings are unsuitable for conventional flight; instead, thrips exploit an unusual mechanism, clap and fling, to create lift using an unsteady circulation pattern with transient vortices near the wings.
Bactrocera dorsalis, previously known as Dacus dorsalis and commonly referred to as the oriental fruit fly, is a species of tephritid fruit fly that is endemic to Southeast Asia. It is one of the major pest species in the genus Bactrocera with a broad host range of cultivated and wild fruits. Male B. dorsalis respond strongly to methyl eugenol, which is used to monitor and estimate populations, as well as to annihilate males as a form of pest control. They are also important pollinators and visitors of wild orchids, Bulbophyllum cheiri and Bulbophyllum vinaceum in Southeast Asia, which lure the flies using methyl eugenol.
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Spinosad is an insecticide based on chemical compounds found in the bacterial species Saccharopolyspora spinosa. The genus Saccharopolyspora was discovered in 1985 in isolates from crushed sugarcane. The bacteria produce yellowish-pink aerial hyphae, with bead-like chains of spores enclosed in a characteristic hairy sheath. This genus is defined as aerobic, Gram-positive, nonacid-fast actinomycetes with fragmenting substrate mycelium. S. spinosa was isolated from soil collected inside a nonoperational sugar mill rum still in the Virgin Islands. Spinosad is a mixture of chemical compounds in the spinosyn family that has a generalized structure consisting of a unique tetracyclic ring system attached to an amino sugar (D-forosamine) and a neutral sugar (tri-Ο-methyl-L-rhamnose). Spinosad is relatively nonpolar and not easily dissolved in water.
Impatiens necrotic spot orthotospovirus(INSV) is a plant pathogenic virus of the order Bunyavirales. It was originally believed to be another strain of Tomato spotted wilt virus, but genetic investigations revealed them to be separate viruses. It is a negative-strand RNA virus which has a tripartite genome. It is largely spread by the insect vector of the western flower thrips. The virus infects more than 648 species of plants including important horticultural and agricultural species such as fuchsia, tomato, orchids, and lettuce (especially romaine). As the name implies, the main symptom on plants is necrotic spots that appear on the leaves. The INSV virus infects by injecting the RNA the virus contains into the cell which then starts using the cell resources to transcribe what the virus RNA states. Viral infection can often result in the death of the plant. The disease is mainly controlled by the elimination of the western flower thrip vector and by destroying any infected plant material.
The western flower thrips [Frankliniella occidentalis (Pergande)] is an invasive pest insect in agriculture. This species of thrips is native to the Southwestern United States but has spread to other continents, including Europe, Australia, and South America via transport of infested plant material.
Orthotospovirus is a genus of negative-strand RNA viruses, in the family Tospoviridae of the order Bunyavirales, which infects plants. Tospoviruses take their name from the species Tomato spotted wilt orthotospovirus (TSWV) which was discovered in Australia in 1919. TSWV remained the only known member of the family until the early 1990s when genetic characterisation of plant viruses became more common. There are now at least twenty species in the genus with more being discovered on a regular basis. Member viruses infect over eight hundred plant species from 82 different families.
Bactrocera cucurbitae, the melon fly, is a fruit fly of the family Tephritidae. It is a serious agricultural pest, particularly in Hawaii.
Thrips palmi is an insect from the genus Thrips in the order Thysanoptera. It is known commonly as the melon thrips.
The Thripinae are a subfamily of thrips, insects of the order Thysanoptera. The Thripinae belong to the common thrips family Thripidae and include around 1,400 species in 150 genera. A 2012 molecular phylogeny found that the Thripinae was paraphyletic; further work will be needed to clarify the relationships within the group.
Dicyphus hesperus is a species of true bug in the family Miridae. It is a generalist predator of other insects and also feeds on plant tissues. It is native to North America and has been used there in biological control of agricultural pests, especially whitefly on tomatoes.
Thrips tabaci is a species of very small insect in the genus Thrips in the order Thysanoptera. It is commonly known as the onion thrips, the potato thrips, the tobacco thrips or the cotton seedling thrips. It is an agricultural pest that can damage crops of onions and other plants, and it can additionally act as a vector for plant viruses.
Frankliniella schultzei, the common blossom thrips or cotton thrips, is a species of thrips in the family Thripidae. It is found in many parts of the world and is an important pest insect in agriculture.
Heliothrips haemorrhoidalis is a species of thrips in the family Thripidae. It is most commonly known as the greenhouse thrips, the glasshouse thrip or black tea thrips. This species of thrips was first described in 1833 by Bouché in Berlin, Germany. H. haemorrhoidalis also has many synonyms depending on where they were described from such as: H. adonidum Haliday, H. semiaureus Girault, H. abdominalis Reuter, H. angustior Priesner, H. ceylonicus Schultz, Dinurothrips rufiventris Girault. In New Zealand, H. haemorrhoidalis is one of the four species belonging to the subfamily Panchaetothripinae.
Panchaetothripinae is a subfamily of thrips in the family Thripidae, first described in 1912 by Richard Siddoway Bagnall. There are about 11 genera and more than 50 described species in Panchaetothripinae.
Echinothrips americanus is a species of thrips in the family Thripidae. It is found in North America, Europe, and Asia. E. americanus was first described in 1913 by entomologist A.C. Morgan in Quincy, Florida, where he found the insect on a Veratrum viride plant. Suggested common names include Poinsettia thrips and Impatiens thrips. Since their spread throughout Europe as early as 1995, and subsequently China, E. americanus has been called an "upcoming pest."
Pepper leaf curl virus(PepLCV) is a DNA virus from the genus Begomovirus and the family Geminiviridae. PepLCV causes severe disease especially in pepper (Capsicum spp.). It can be found in tropical and subtropical regions such as Thailand and India, but has also been detected in countries such as the United States and Nigeria. This virus is transmitted by an insect vector from the family Aleyrodidae and order Hemiptera, the whitefly Bemisia tabaci. The primary host for PepLCV are several Capsicum spp.. PepLCV has been responsible for several epidemics and causes severe economic losses. It is the focus of research trying to understand the genetic basis of resistance. Currently, a source of resistance to the virus has been identified in the Bhut Jolokia pepper.
Scirtothrips aurantii is a thrips pest of Citrus spp., Mangifera indica, Musa × paradisiaca, Musa acuminata, and Camellia sinensis.
Pezothrips kellyanus, also known as Kelly's citrus thrips, is a species of Thysanoptera (thrips) from the family Thripidae. It is known as a pest species on citrus fruit crops as it can cause scarring damage to fruit skins.