Today … Insecta, Pterygota Neoptera Orthoptera Dictyoptera Mantodea (mantids) Isoptera (termites) Blattaria (cockroaches) Thysanoptera Hemipteroids Hemiptera Thysanoptera Psocodea (Psocoptera) Endopterygota RPB 2009; thysanoptera v. 2.4

Major features of Thysanoptera More basic facts about thrips:

• Name comes from the Greek for • Piercing/sucking mouthparts. Most feed on fringed wings. Also known as vascular , but some on fungi or mosses. ‘thunderflies’ or ‘stormflies’ Often seen on flower heads. Some species are predatory. • Adults 0.5-15mm but temperate species rarely >2mm • Some thrips are pests of a wide range of crops e.g. cereals, vegetables, flowers, cotton, citrus • About 5,000 described species. etc. Damage is direct to flowers, fruit and leaves, • Widely distributed in Latitudes also indirect by virus transmission e.g. Tomato between 60N and 45S. spotted wilt virus (TSWV) • Usually both genders, but females • Some thrips are beneficial as pollinators and as predominate. Males are haploid. natural enemies of mites, scales and pest thrips. Some species are wholly Some are also useful for weed control. parthenogenetic (or the males are unknown).

Thrips damage: primarily cosmetic Thrips damage Courtesy: www.realipm.comCourtesy:

excrement/frass … with flowers this matters!

1 Principal features Typical wing of an adult thrips tarsi with bladder pronotum mouth cone • unique asymmetrical metanotum mouthparts; abd. seg. 1 • tarsi with apical eversible bladders; • wings (if present) hair fringed and narrow; • … but adults may be: macropterous, brachypterous or apterous. abdominal segment 10 (ovipositor) Dorsal Ventral

Taxonomy of thrips: 2 suborders Sub-order: Forewings veined Terebrantia Tubulifera Wings at rest parallel to each other Seven families, One family, the two are of economic Rear abdomen importance - the (includes pest and conical and natural enemy spp.) In female, single pupal stage Saw-like ovipositor

Sub order family No of Comment (UK) Sub-order: Tubulifera species Terebrantia Uzelothripidae 1 0 Forewings lack 15 0 Neotropical fungal feeders veination * Aeolothripidae 260 13 Mainly Wings at rest overlap temperate, Two pupal stages flower-living separated by a moult predators * 5 0 4 0 Rear abdomen 70 0 New World tubular Thripidae 1700 107 No ovipositor Tubulifera Phlaeothripidae 3000 39 * *

2 The mouthcone and mouthparts Side view of adult thrips showing mouthcone NB asymmetrical compound mouthparts - prothorax eye here shown consuming a pollen grain

antenna

mouthcone ovipositor

Feeding by thrips Feeding scars • Mouthparts form a cone attached to underside of head and directed downwards beneath the first thoracic segment. Uniquely asymmetrical with a single piercing mandible and two maxillary stylets forming feeding tube. • Cell contents (including pollen & chloroplasts) ingested whole, thrips can consume 12% of their body weight per hour. • Feeding sites on plants: leaves, flowers, florets and seeds. • Direct damage: probing and feeding removes surface waxes, epidermal cells collapse and mesophyll cells are destroyed. Tissues then develop a silvery sheen and areas coalesce and wrinkle.

Biology and Ecology Indirect damage • Haploid males develop from unfertilised eggs. Females • Virus transmission of predominate especially in glasshouses where populations tomato spotted wilt virus may be entirely parthenogenetic. (TSWV) and peanut • Females produce 30-300 eggs, which are either surface yellow spot (PYS). deposited or embedded in tissue • Life cycle can last from 10 days to 1 year depending on the • To become infective the temperature. In temperate regions 1-2 generations per year. Over-wintering life stage (egg, pupa, adult) depends thrips must feed on an on species. 12-15 generations per year in warmer climates infected plant during its where the peak populations can exceed 10 Million larval stage. individuals per Hectare. • Weak fliers (10-50 cm/s) but can be windblown to disperse > 100km. Photo: Paul Bachi, www.bugwood.org Bachi, Paul Photo: (Transmitted by 9 spp. in USA)

3 Thysanoptera: Hemimetabolous development • Life cycle evolution: intermediate between Immature life stage of incomplete & complete Caliothrips fasciatus, metamorphosis: egg, 2 the bean thrips, a actively feeding ‘larval’ typical terebrantian instars, pre-pupa, pupa, adult. • Hemimetabolous nymphs, but the term ‘larva’ is used. • Many terebrantians move to soil to pupate, many tubuliferans remain on host plant.

Adaptive forms in thrips

a) Podothrips grass dweller Immature life b) Selenothrips foliage stages of feeder Haplothrips c) Arachisothrips peanut- winged thrips leucanthemi, d) fast- a typical running predator tubuliferan e) Hoplothrips flattened crevice dweller f) Leptogastrothrips ant mimic g) Kladothrips bubble leaf- gall thrips

Some major pest thrips Thysanopteran pests Family Genus Example Major hosts • Piercing/scraping outer plant cells Thripidae Caliothrips C. fasciatus – bean thrips Legumes • Especially cosmetic damage to high value C. sudanensis cotton horticultural crops – cotton leaf thrips •In UK, Kakothrips robustus Heliothrips H. haemorrhoidalis Polyphagous responsible for mottled – black tea or silvery pea pods Greenhouse thrips Hercinothrips H. bicinctus banana Bananas & thrips glasshouses

Scirtothrips Citrus thrips S. aurantii, Citrus S. citri, S.dorsalis Limothrips L. cerealium Cereals & - grain thrips grasses

4 Some more major pest thrips Family Genus Example Major hosts Controlling thrips - Cultural methods: Thripidae F. occidentalis Both v. polyphagous – western flower thrips • Irrigate to avoid water stressed plants. F. schulzei - cotton bud thrips NB watering can also physically remove thrips • Cultivation and burning regimes, crop rotation Thrips T. tabaci onion v. polyphagous, thrips onions, tomatoes • Planting and harvesting times T. angusticepss polyphagous, apple, • Increase plant spacing: when there is a need to – cabbage thrips pear, brassicas to reduce virus incidence T. palmi polyphagous, vegetables, • Control alternative hosts – crop and weed ornamentals Phlaeothripidae Gigantothrips G. elegans Leaf curl on figs

Cultural controls in practice Controlling thrips - Chemical

Remove open or unwanted flowers • Difficult as they hide in confined spaces Thrips lay eggs in Bins for reject • ‘Thripstick’ – sticky polybutene + flowers flowers – with lids deltamethrin (sprayed onto plastic surfaces under cucumber plants against T. tabaci) • Synthetic pyrethroids & neo-nicotinoids may interfere with IPM Courtesy: www.realipm.comCourtesy: • Application …

Trap crops

…at very high volume rates Thrips: Biological controls

• Predatory mites: Amblyseius (Neoseiulus) cucumeris • Orius spp. (pirate bugs) • Lacewing larvae • Predatory thrips …

5 Beneficial thrips Microbial agents • NATURAL ENEMIES OF PESTS • Aeolothripidae: • Entomopathogenic Aeolothrips – thrips, mites, moth eggs nematodes: Steinernema Franklinothrips – thrips, mites, feltiae & Heterorhabditis spp. • Lecanicillium (Verticillium) • Thripidae lecanii Scolothrips – tertranychid mites • Phlaeothripidae Aleurodothrips ) Karnyothrips ) coccids, scales Leptothrips ) mites etc Podothrips )

Monitoring thrips Yellow traps work as well Pest example: Western Flower thrips, as blue Frankliniella occidentalis (Pergande) Used for monitoring to initiate sprays – spot • Adults <2mm long, yellow-brown in colour, but treatment or overall? several colour forms occur which vary in abundance according to season Risk of large traps for • Highly polyphagous species - 244 recorded hosts mass trapping – may including flowers of apricots, plums, peas, tomatoes, encourage invasions roses, cucurbitaceae, chrysanthemums from outside • Feeding causes discoloration and scarring of blooms and petals and deformed buds; one of the ‘Thripline’: synthetic version of a transmitters tomato spotted wilt virus (TSWV) sexual aggregation pheromone • Easily dispersed on wind, clothes, equipment, plants for Western Flower Thrips, (natural pheromone produced by males and attracts & cut flowers both males and females into mating aggregations)

Western Flower thrips (ctd.) Thrips palmi • Invasive species - spreading rapidly • In USA glasshouses 12-15 generations per year. in tropics and sub-tropics – Eggs inserted into parenchyma cells of leaves, flowers & buds, hatch 4 days at 27ºC, • Polyphagous pest of Cucurbitacae – 2 larval stages, pre-pupal & pupal stage. Pupates in soil. and Solanacae (“melon thrips”) – >50 eggs per female. 80% female • Kept out of Europe despite a • Control: phytosanitary measures, quarantine, biocontrols. number of outbreaks (UK Chemical control difficult because of cryptic habits & infestation imported on cut flowers) insecticide resistance. - all successfully eradicated • Mix of IPM measures: – Space treatments with OP/pyrethroids – Imidacloprid (a neo-nicotinoid) - NL – Sanitation with winter break in glasshouses (UK)

See: Cannon et al. (2007) Crop Protection 26 Frankliniella occidentalis

1089-1098 http://www.insectimages.org/ DEFRA

6 Beneficial thrips Summary : Thysanoptera • REDUCING FITNESS OF WEEDS • “Fringed wings” - coupled by tiny hooks on hind wings - • Liothrips urichi to control Clidemia sometimes called “thunder flies” • Amynothrips andersoni to control alligator • Two sub-orders: weed in southern USA – Terebrantia: 7 families including Thripidae – Tubulifera: 1 family the Phlaeothripidae • Small, slender, usually dark , commonly associated with flowers • Piercing asymetrical mouthparts • Pest species - often significant cosmetic damage; may transmit viruses • POLLINATION – useful when large insects • Beneficial spp. - especially pollinators and predators of such as bees are rare thrips mites and Sternorrhyncha

Further Reading Trevor Lewis (1973) Thrips. Academic Press

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