Scirtothrips mangiferae Priesner, 1932

Thripinae, Thripidae, Terebrantia, Thysanoptera

Figures

Fig. 1: Terminal segments VI-VIII, pedicel and segments III and IV with forked sense cone, 8-segmented antenna
Fig. 2: Head dorsal with scape and pedicel
Fig. 3: Pronotum
Fig. 4: Meso- and metanotum
Fig. 5: Fore- and hind wing
Fig. 6: Basal region of fore wing
Fig. 7: Tergite VIII

Scirtothrips mangiferae causes leaf curling on various fruit trees, particularly on mango but also citrus, cotton and grape. Both sexes fully winged. Body yellow; without dark brown antecostal ridges on tergites and sternites and brown tergal area medially; antennal segment I white, II & III basally yellow, remainder more or less brown; fore wings pale and weakly shaded. Antennae 8-segmented; segments III & IV with constricted apical neck and sense cone forked and stout (Fig. 1). Head wider than long; ocellar triangle and postocular region with closely spaced sculpture lines; 3 pairs of ocellar setae, pair I short and behind base of scape and in front of anterior ocellus, pair III arising close together within ocellar triangle anterior to tangent of anterior margin of hind ocelli (Fig. 2). Pronotum with closely spaced transverse sculpture lines; posterior margin with 4 pairs of setae, S2 prominent and elongate, S3 moderately long (Fig. 3). Meso- and metafurca with spinula. Metanotal median area sculptured lines transverse at anterior, but with irregular equiangular or longitudinal reticulations near posterior; median setae at anterior margin; campaniform sensilla absent (Fig. 4). Mid and hind tarsi 2-segmented. Fore wing first vein with 3 setae on distal half; second vein with 3 or 4 widely spaced setae; posteromarginal cilia wavy; clavus with 4 veinal setae (Fig. 5 and 6). Tergites III-VII with median setae small but close together; II-VIII with lateral thirds covered in closely spaced, regualr rows of fine microtrichia, these microtrichial fields with 4-6 discal setae, posterior margin of these tergites with fine comb laterally; VIII with comb complete across posterior margin, and a patch of microtrichia anteromedially (Fig. 7); tergite IX with several rows of discal microtrichia. Sternites without discal setae; covered with rows of microtrichia restricted to lateral thirds of discal area; posterior margins with comb of short microtrichia between marginal setae; median setae on VII arising at margin.
Male similar to female; tergite IX posterior angles bearing pair of stout curved processes (drepanae) extending across tergite X; sternites without glandular areas.

The genus Scirtothrips Shull, 1909
Scirtothrips currently includes more than 100 described species from temperate, subtropical and tropical areas of the world. Several species are serious crop pests. All of them have many regular rows of microtrichia on the lateral sides of the tergites (species of the genus look a like minute fur-bearing animals), and a complete posteromarginal comb of microtrichia on tergite VIII. These are small, usually pale yellow thrips with 8-segmented antennae, segments III and IV with forked sense cone, ovipositor well sclerotized and makes slide preparation often very complicate. Surface of pronotum closely transversely striate, the fore wings are narrow with only a few distal setae on the first vein and a few apical setae on the second vein. Mound & Palmer (1981) present a key to the major pest species, and Mound & Marullo (1996) a key to the species of Central America. Johansen & Mojica-Guzmán (1998) described 33 species from Mexico, particularly from mango and avocado trees, but doubts have been expressed concerning the systematical validity of some of these species (Mound & zur Strassen 2001). Hoddle & Mound (2003) provided information on 21 Scirtothrips species from Australia, and Rugman-Jones et al. (2006) produced a molecular key to several pest species in this genus. Relationships of various Scirtothrips species based on molecular data are further considered by Hoddle et al. (2008) and a molecular identification method was given by Moritz et al. (2000) and used for the first time in combintion with LucID (Moritz et al. 2004).

Scirtothrips mangiferae differs from other species of this genus in lacking dark brown antecostal ridges on tergites and sternites, in lacking brown color patterns on tergites medially, and in having 4-6 setae on tergal microtrichial field laterally (other species with dark brown antecostal ridges on tergites and sternites, a small brown tergal area medially, and 3 setae on tergal microtrichial field laterally). Most of Scirtothrips species usually have a mainly yellow body color, fore wings uniformly light brown or pale, and a patch of microtrichia anteromedially on tergite VIII (except for Scirtothrips kenyensis with a light brown body color, uniformly dark brown fore wings, and without microtrichia anteromedially on tergite VIII), and have the metanotal median setae arising at anterior margin (only in Scirtothrips dorsalis metanotal median setae arising behind anterior margin). Scirtothrips mangiferae as well as Scirtothrips kenyensis have ocellar setae III arising anterior to tangent of anterior margin of hind ocelli (Scirtothrips aurantii with pair III arising between anterior margin of hind ocelli; Scirtothrips dorsalis with pair III between median points of hind ocelli). The fore wing posterior margin cilia of Scirtothrips mangiferae and Scirtothrips aurantii are undulated at least in distal part (compared to Scirtothrips kenyensis and Scirtothrips dorsalis with straight cilia). Scirtothrips mangiferae as well as Scirtothrips dorsalis have microtrichia medially on tergite IX (in Scirtothrips aurantii and Scirtothrips kenyensis absent). And the sternites of Scirtothrips kenyensis and Scirtothrips mangiferae exhibit microtrichia restricted to lateral thirds of discal area (compared to Scirtothrips aurantii and Scirtothrips dorsalis with a strong microtrichial field extending fully across discal area).
Kenyattathrips katarinae is related to species of Scirtothrips. All of them have many regular, closely spaced rows of fine microtrichia on the lateral sides of the tergites and a complete posteromarginal comb on tergite VIII, antennal segments III & IV with forked sense cone, and the pronotum of these thrips is closely and transversely striate. Compared to Kenyattathrips katarinae, all species of Scirtothrips have 8-segmented antennae, antennal segment II without an exeptionally long seta at the inner apex, ocellar setal pair I short and behind base of scape and in front of anterior ocellus, only 1-2 pairs of elongate pronotal setae and no long anteromarginal setae on the pronotum, metanotum reticulated medially, fore wings second vein with a few apical setae, and tergite VII bears the posteromarginal comb of microtrichia only laterally. Whereas Kenyattathrips katarinae has 7-segmented antennae, antennal segment II with an exceptionally long seta at the inner apex, a long ocellar setal pair I placed far forward on the inter-antennal projection, 3-4 pairs of elongate pronotal setae (1 pair anteromarginally, 1 pair moderately elongate laterally, 2 pairs posteromarginally), a metanotum without or with weakly sculpture medially, an almost complete row of setae on fore wing second vein, and a complete posteromarginal comb of microtrichia on tergite VII. Furthermore, species of Scirtothrips are similar to Neohydatothrips samayunkur and Hydatothrips adolfifriderici in having the surface of lateral thirds of tergites bearing many regular rows of fine microtrichia. Neohydatothrips samayunkur and Hydatothrips adolfifriderici have ocellar setae III on head arising on anterior margin, or in front of, ocellar triangle, fore wings with a complete row of setae on the first vein and without or only 2 setae on the second vein, and a distinctive colored and/or sculptured area on the pronotum, the pronotal blotch. Like species of the genus Scirtothrips, also Florithrips has pleurotergites and tergites laterally covered with fine microtrichia, but in Scirtothrips these are arranged in closely spaced rows, whereas in Florithrips traegardhi these extend along lines of sculpture. In addition, tergites II-VII of Scirtothrips species have a fine comb laterally at posterior margin, and sternites covered with rows of microtrichia, which lacking in Florithrips traegardhi.

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 and adults may live for more than one month producing several generations in one year depending on seasonal weather.

Host plants
Crops: citrus, cotton, grape, mango, peach.

Vector capacity
None identified, but possible mechanical distribution of phytopathogenic fungi and bacteria.

Damage and symptoms
All of the members of this group feed on the leaves of their plant hosts and are quite cryptic in habit.Scirtothrips mangiferae only be found on the very young, tender leaves, and on the buds of the trees, especially when the mango trees have the characteristically reddish colored young foliage (Priesner 1932). It causing the young leaves to curl along the midrib, distorting their shape, and leading to premature drop. The twigs of infested shoots are much shorter than those of uninfested ones (Wysoki et al. 1993).

Detection and control strategies
Application of neem products are reported to be effective against Scirtothrips mangiferae (Kumar & Bhatt 1999).

Biogeography

Afrotropical and Eastern Mediterranean. Egypt (Eilat), Gabon, Libya, Sudan.

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Kumar S & Bhatt RI (1999). Field evaluation of plant leaf extracts oil and neem products against mango hopper (Amritodus atkinsoni Leth.) and thrips (Scirtothrips mangiferae Hood). Allelopathy J., 6: 271-276.

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