Thrips parvispinus (Karny, 1922)

Thripinae, Thripidae, Terebrantia, Thysanoptera

Figures

Fig. 1: 7-segmented antenna, segments III and IV with forked sense cone, terminal segments V-VII
Fig. 2: Head dorsal with ocellar triangle
Fig. 3: Pronotum
Fig. 4: Meso- and metanotum
Fig. 5: Fore wing and fore wing middle region
Fig. 6: Sternites VI and VII
Fig. 7: Tergites VI and VII
Fig. 8: Tergites VII and VIII
Fig. 9: Tergites VIII and IX

Thrips parvispinus is a polyphagous thrips breeding in flowers and on young leaves of papaya, pepper and potato, and are key pest of Gardenia plants. Both sexes fully winged. Body brown; head and thorax paler than abdomen; head commonly with cheeks darker than median area; legs mainly yellow; antennal segment III yellow, also basal half of IV & V; fore wings brown with base sharply pale. Antennae 7-segmented; segments III & IV elongate with apex constricted and forked sense cone (Fig. 1). Head wider than long; with 2 pairs of ocellar setae, pair I absent, pair III small and arising on anterior margins of ocellar triangle; postocular setae I & III about as long as ocellar setae III, postocular setae II minute (Fig. 2). Pronotum with 2 pairs of long posteroangular setae; posterior and anterior margin each with 3-4 pairs of setae (Fig. 3). Mesofurca with spinula. Metanotum with mainly equiangular reticulation, reticles varying in shape and sometimes with faint internal sculptured markings; median setae longer than lateral setae and arising well behind anterior margin; campaniform sensilla absent (Fig. 4). Mid and hind tarsi 2-segmented. Fore wing first and second vein with complete rows of setae; clavus with 5 marginal setae, clavus terminal seta longer than subterminal seta (Fig. 5). Tergite II with 3 or 4 lateral marginal setae; V-VIII with ctenidia present laterally, on VIII posteromedial to spiracles; posterior margin of VIII with comb almost absent, a few microtrichia present laterally (Fig. 7-9); pleurotergites without discal setae. Sternite II with 2 pairs of marginal setae, III-VII with 3 pairs, median marginal setae on VII arising in front of posterior margin; sternites II & VII without discal setae, III-VI with 6-13 discal setae in an irregular row (Fig. 6).
Male largely yellow; tergite VIII with no posteromarginal comb; tergite IX setae S1 slightly longer than S2, bases equidistant; sternites III-VII each with small transverse glandular area, discal setae arising laterally.

The genus Thrips L., 1758
There are nearly 300 species currently recognized in the genus Thrips making this genus one of the largest taxa within the order Thysanoptera. The genus was redefined progressively during the 1970's (see Mound et al. 1976), to include many species previously placed in Taeniothrips. The genus Thrips now includes a range of species, some with the antennae 7-segmented, others 8-segmented, and a few with the number of segments varying between 7 and 8. Similarly, some species have few setae on the fore wing first vein, whereas others have a complete row of setae on this vein. The species with a complete setal row on the first vein were placed from some taxonomists in the genera Isothrips or Isoneurothrips. However, all of the species in Thrips have the following character states: antennal segments III & IV with forked sense cone, absence of ocellar setae I, pronotum with 2 pairs of elongate posteroangular setae, paired ctenidia laterally on the tergites V-VIII, tergite VIII ctenidium arising posterior to the spiracle (in contrast to species of the genus Frankliniella). Other character states, such as number of antennal segments, number of setae on the fore wing veins, and number of discal setae on the abdominal sternites are variable between species (Mound & Masumoto 2005; Nakahara 1994; Palmer 1992). Identification keys are available for the species of this genus from many parts of the world. Of particular importance is the published key by Mound (2010) for members of the genus Thrips from Afro-tropical region as well as previous Lucid keys from Moritz et al. (2001, 2004, 2009).

Thrips parvispinus is very similar to some other Thrips species - like Thrips orientalis. Thrips parvispinus has discal setae on sternites III-VI but not on sternite VII, and no discal setae on pleurotergites (Thrips australis, Thrips microchaetus, Thrips subnudula and Thrips tenellus, all of them have sternites III-VII with at least 1 pair of discal setae and pleurotergites with discal setae; Thrips acaciae, Thrips brevisetosus, Thrips florum, Thrips gowdeyi, Thrips hawaiiensis and Thrips simplex, all of them have sternites III-VII with at least 1 pair of discal setae and pleurotergites without discal setae; Thrips nigropilosus, Thrips palmi, Thrips pusillus and Thrips tabaci, all of them have sternites and pleurotergites without discal setae).
Thrips parvispinus differs from Thrips orientalis in having sternites III-VI with 6-13 discal setae in an irregular row, metanotal equiangular reticulations rarely with faint internal sculptured markings, brown fore wings with base sharply paler, on fore wing clavus the terminal veinal seta is longer than subterminal seta, and the fore wing first vein setal row is complete. Thrips orientalis has sternites III-VI with no more than 6 discal setae placed laterally, metanotal equiangular reticulations with many conspicuous internal sculptured markings, brown fore wings only with small white spot near veinal fork, on fore wing clavus the terminal veinal seta is shorter than subterminal seta, and the fore wing first vein is highly variable on distal half, from almost complete to only 2 setae medially and 4 distally. Outside this group, the species is similar to Thrips australis in having a metanotal median sculpture with mainly equiangular reticulation, the fore wing first vein with setal row complete, and the comb of tergite VIII is present laterally and absent medially.
Species of the genus Thrips are similar to species of Stenchaetothrips, Microcephalothrips abdominalis, Larothrips dentipes and Fulmekiola serrata because of tergites V-VIII bear a pair of ctenidia laterally, which placed on tergite VIII posteromedial to the spiracle, and all species have no ocellar setae I. In contrast to species with craspedum on tergites II-VII (Microcephalothrips abdominalis, Larothrips dentipes and Fulmekiola serrata), species of Thrips and Stenchaetothrips have no posteromarginal craspedum on tergites and sternites. Species of the genus Thrips as well as Fulmekiola serrata and species of Stenchaetothrips have 2 pairs of elongate posteroangular setae (Microcephalothrips abdominalis with 2 pairs of moderately elongate pronotal setae and Larothrips dentipes without elongate setae). Compared to the species of Thrips, Microcephalothrips abdominalis, and Larothrips dentipes, which have ocellar setae II on head much shorter than or about as long as III, Fulmekiola serrata and species of Stenchaetothrips have ocellar setae II much longer than III, and sternites always without discal setae.

Life history
As with other thrips species the life cycle from egg to adult is dependent on temperature. The full cycle can take about 15 days (Lewis 1973) to over a month. Adults may live for more than one month producing several generations in one year depending on seasons. The development period ranged from 18.8 days at 30°C to 37.6 days at 20°C and the adult fecundity ranged from 50-69 eggs per female (Murai et al. 2010).

Host plants
Polyphagous. Black Jack (Bidens pilosa), coffee, Gardenia sp., papaya, chilli pepper, paprika, potato, tobacco, Vigna sp., green bean, strawberry, eggplant, watermelon and other Cucurbitaceae.

Vector capacity
Tobacco streak virus (TSV). Mechanical transmission of Cladosporium oxysporum causing bunchy-top, i. e. malformed leaves and shot holes on new flushes (Lim 1989).

Damage and symptoms
This polyphagous species has been recorded as a serious pest of Gardenia and as a moderate pest on several of its host plants as a result from the damage caused by feeding and breeding on the young leaves and flowers. Infested leaves lightly mottled and streaked. Recently Thrips parvispinus has been observed as key pest of chilli pepper and strawberry. In Indonesia it has replaced Thrips palmi as the key thrips on vegetables (Murai et al. 2010).

Detection and control strategies
Thrips parvispinus are attracted to white rather than blue or yellow (Murai et al. 2010). Chilli pepper lines resistant to Thrips parvispinus have been identified (Maharijaya et al. 2011). Laboratory studies indicated that they are susceptible to spinosad and not to acetamiprid (Murai et al. 2010). Ladybird beetles, Menochilus sexmaculatus and Coccinella transversalis were observed as potential natural enemies of this species in Indonesia. Entomopathogenic fungus Verticillium lecanii (=Lecanicillium longisporum) and Beauveria bassiana are reported to be effective for against Thrips parvispinus management. Use of Menochilus sexmaculatus and entomopathogenic fungus, Verticillium lecanii (=Lecanicillium longisporum) was as effective as pesticide application for management of Thrips parvispinus (Prabaningrum et al. 2006).
Exposure to 60% CO₂ atmospheres at 30°C results in 100% mortality of five different thrips species, Frankliniella occidentalis (Pergande), Frankliniella intonsa (Trybom), Thrips tabaci Lindeman, Thrips palmi Karny, and Thrips parvispinus Karny (Seki & Murai 2012).

Biogeography

Asia, Australia, New Zealand, Europe, Africa. La Réunion, Tanzania (Dar-el-Salaam), Uganda (Kampala).

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