Scirtothrips kenyensis Mound, 1968

Thripinae, Thripidae, Terebrantia, Thysanoptera

Figures

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

Scirtothrips kenyensis causes serious damage to very young leaves of tea and coffee. Both sexes fully winged. Body mainly light brown; with posterior margin of head behind eyes almost black; brown shadings between bases of antennae, on lateral thirds of pronotum, on anterior margin of mesonotum, posterolaterally on metanotum, and in median third of tergites II-IX; dark brown antecostal ridge on tergites and sternites; antennae and fore wings uniformly dark brown. 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 widely spaced setae; posteromarginal cilia straight; clavus with 4 veinal setae (Fig. 5). Tergites III-VI with median setae small but close together (Fig. 6); VII & VIII with median setae distinctly longer than III-VI; II-VIII with lateral thirds covered in closely spaced, regular rows of fine microtrichia, these microtrichial fields with 3 discal setae, posterior margin of these tergites with fine comb laterally; VIII with comb complete across posterior margin (Fig. 7), and without a patch of microtrichia anteromedially; tergite IX with no 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 posterior margin.
Male similar to female but tergites and sternites without dark brown antecostal ridges; 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 kenyensis differs from other species of this genus in having a darker, light brown body color, uniformly dark brown fore wings, and in lacking microtrichia anteromedially on tergite VIII (compared to other species with mainly yellow body color, fore wings uniformly light brown or pale, and with a patch of microtrichia anteromedially on tergite VIII). Most of Scirtothrips-species have a dark brown antecostal ridge on tergites and sternites, a small brown tergal area medially, and 3 setae on tergal microtrichial field laterally (except for Scirtothrips mangiferae which has no dark brown antecostal ridge on tergites and sternites nor any distinctive color patterns on tergites, and 4-6 setae on tergal microtrichial field laterally), and the metanotal median setae arising at anterior margin (only in Scirtothrips dorsalis those arising behind anterior margin). Scirtothrips kenyensis as well as Scirtothrips mangiferae 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 kenyensis and Scirtothrips dorsalis are straight (compared to Scirtothrips aurantii and Scirtothrips mangiferae with cilia undulated at least in distal part). Scirtothrips kenyensis as well as Scirtothrips aurantii have no microtrichia medially on tergite IX (in Scirtothrips dorsalis and Scirtothrips mangiferae microtrichia medially present). 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 on 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. 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. But 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
Chard (Beta vulgaris var. cicla), coffee (Coffea arabica), tea.

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. As with other species of the genus it attacks growing tissue, that is, young plants and recently pruned bushes (Mound 1968).

Detection and control strategies
Natural pyrethrum formulation (25EC) and permethrin (25EC) were effective against Scirothrips kenyensis infesting tea (Sudoi et al. 1989).

Additional notes
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Biogeography

East Africa. Kenya (Nyanza Province, Kericho, Kimari Estate), Rwanda (Rubona), Uganda (Toro Province, Fort Portal).

Hoddle, MS, Heraty JM, Rugman-Jones PF, Mound LA & Stouthamer R (2008). Relationships among species of Scirtothrips (Thysanoptera: Thripidae, Thripinae) using molecular and morphological data. Annals of the Entomological Society of America. 101 (3): 491-500

Hoddle MS & Mound LA (2003). The genus Scirtothrips in Australia (Insecta, Thysanoptera, Thripidae). Zootaxa. 268: 1-40

Johansen RM & Mojica-Guzmán A (1998). The genus Scirtothrips Shull, 1909 (Thysanoptera: Thripidae, Sericothripini), in Mexico. Folia Entomologica Mexicana. 104: 23-108

Lewis T (1973). Thrips: Their biology, ecology and economic importance. Academic Press Inc., London Ltd., 349 pp

Lewis T (1997). Thrips as crop pests. CAB International, Wallingford, 740 pp

Moritz G, Delker C, Paulsen M, Mound LA, Burgermeister W (2000). Modern methods in thrips-identification and information (Insecta, Thysanoptera). Bulletin OEPP/EPPO (Paris) 30: 591-593

Moritz G, Mound LA, Morris DC & Goldarazena A (2004). Pest thrips of the world - an identification and information system using molecular and microscopical methods. Centre for Biological Information Technology, University of Queensland, Australia, CDROM ISBN 1 86499 781 8

Mound LA (1968). A new species of Scirtothrips from Kenya attacking tea, with synonymic notes on two related pest species. Bulletin of Entomological Research. 57 (4): 533-538

Mound LA & Marullo R (1996). The thrips of Central and South America: An introduction (Insecta: Thysanoptera). Memoirs on Entomology, International, Vol. 6. Associated Publishers, Gainsville, 487 pp.

Mound LA & Palmer JM (1981). Identification, distribution and host-plants of the pest species of Scirtothrips (Thysanoptera: Thripidae). Bulletin of Entomological Research. 71: 467-479

Mound LA & zur Strassen R (2001). The genus Scirtothrips (Thysanoptera: Thripidae) in Mexico: a critique of the review by Johansen & Mojica-Guzmán (1998). Folia Entomologica Mexicana. 40: 133-142

Palmer JM (1990). Identification of the common thrips of Tropical Africa (Thysanoptera, Insecta). Tropical Pest Management. 36 (1): 27-49

Palmer JM, Mound LA & du Heaume GJ (1989). 2. Thysanoptera, 73 pp. In Betts CR [ed.], CIE Guides to insects of importance to man. CAB International, Wallingford, Oxon, UK

Rugman-Jones PF, Hoddle MS, Mound LA & Stouthamer R (2006). Molecular identification key for pest species of Scirtothrips (Thysanoptera: Thripidae). Journal of Economic Entomology. 99 (5): 1813-1819

Sudoi V, Warui C, Ombaka JM. (1989). Field efficacy of formulations containing natural pyrethrum, synthetic pyrethroids and organophosphates for control of yellow tea thrips Scirtothrips kenyensis Mound. Tea-Tea Research Foundation 10 (2): 192 - 195