Frankliniella schultzei (Trybom, 1910)

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: Head dorsal with ocellar triangle
Fig. 4: Pronotum
Fig. 5: Meso- and metanotum
Fig. 6: Fore- and hind wing, fore wing distal region
Fig. 7: Sternites V and VI
Fig. 8: Tergites VII and VIII
Fig. 9: Tergites VIII and IX
Fig. 10: Dark adult female
Fig. 11: Pale adult male
Fig. 12: Pale adult female

Frankliniella schultzei is an important vector of tomato spotted wilt virus, and breeds on the flowers and leaves of many plants. Both sexes fully winged; existing as two discrete color morphs, either body color brown, with pronotum, tibiae and tarsi paler, antennae brown with segments III-V yellow at base, or body color yellow with faint shadings on tergites, and antennal segments VI-VIII brown; fore wings pale with dark setae. Some authors (Bhatti et al. 2009) consider the pale and dark ones as two different species with the pale ones called as Frankliniella sulphurea, while others have synonymized both the pale and dark ones as Frankliniella schultzei. Antennae 8-segmented; segments III & IV with forked sense cone, segment VIII longer, about 1.5 the length of antennal segment VII (Fig. 1). Head wider than long; 3 pairs of ocellar setae present, pair III about as long as distance between hind ocelli and arising close together between anterior margins of hind ocelli; postocular setae pair I present, postocular setae pair IV about as long as distance between hind ocelli (Fig. 2 and 3). Pronotum with 4-5 pairs of elongate setae (1 pair anteromarginally, 1 pair anteroangularly, 2 pairs posteroangularly and 1 pair of moderately elongate posteromarginal submedian setae) (Fig. 4). Mesofurca with spinula. Metanotal median area transverse at anterior and with irregular equiangular or longitudinal reticulations on posterior half; median setae longer than lateral setae and arising at anterior margin; campaniform sensilla absent (Fig. 5). Mid and hind tarsi 2-segmented. Fore wing with 2 complete rows of veinal setae (Fig. 6). Tergites VI-VIII with paired ctenidia laterally, on VIII anterolateral to spiracle; posteromarginal comb on VIII weakly developed or absent (Fig. 8 and 9). Sternites III-VII without discal setae; median setae of sternite VII arising at or close to posterior margin (Fig. 7).
Male similar to female but smaller; tergite VIII with a few teeth laterally on posterior margin, IX with median pair of setae shorter than lateral discal setae; sternites III-VII with broadly transverse glandular area.
Second instar larva white with antennal segments pale grey and tergite X with distinct grey band on posterior half; posterior margin of tergite IX with small teeth; spiracles on VIII small.

The genus Frankliniella Karny, 1910
This genus is mainly known from the New World and contains about 230 species, many of them from the Neotropics (Mound & Marullo 1996, Cavalleri & Mound 2012). Some species are widely known as crop pests - Frankliniella occidentalis, Frankliniella intonsa, Frankliniella schultzei (all of them vectors of tospoviruses) and Frankliniella williamsi. The members in this genus are sometimes quite difficult to separate from one another and the classification has been in flux with many species later synonymized in association with color variations. They mostly have 3 pairs of well developed ocellar setae, 8-segmented antennae with segments III and IV having forked sense cones, usually 4-5 pairs of elongate pronotal setae (1 pair anteromarginally, 1 pair anteroangularly, 2 pairs posteroangularly, and 1 pair of moderately elongate posteromarginal submedian setae S2 which are longer than median seta S1), metanotal median setae arising at anterior margin, when present wings with complete rows of setae on the wing veins, paired ctenidia laterally on tergites V-VIII with those on VIII anterolateral to the spiracles, no discal setae on sternites, and the males are generally smaller and paler than the females (Mound & Marullo 1996; Stannard 1968).

Frankliniella schultzei is exceptional within the genus because ocellar setae III arising very close together between anterior margins of hind ocelli (Frankliniella occidentalis, Frankliniella borinquen and Frankliniella williamsi with ocellar setae III arising on anterior margins of or just within anterior margins of ocellar triangle), metanotal campaniform sensilla are absent (in other species present), and tergite VIII has the posteromarginal comb of microtrichia weakly developed or complete absent (in Frankliniella borinquen and Frankliniella occidentalis the comb on tergite VIII is complete, in Frankliniella borinquen with short microtrichia arising from triangular bases; in Frankliniella occidentalis with short or long microtrichia on broadly triangular bases; Frankliniella williamsi with a comb of long and fine, closely spaced microtrichia on broadly triangular bases). Frankliniella schultzei as well as Frankliniella occidentalis and Frankliniella williamsi with simple pedicel of antennal segment III and antennal segment VIII longer than segment VII (only Frankliniella borinquen with a pedicel of antennal segment III swollen, with edged ring surmounted by a distinctive swelling and a slightly flared collar, and antennal segment VIII equal in length to or shorter than segment VII). In Frankliniella schultzei and Frankliniella williamsi ocellar setae III on head are about as long as distance between hind ocelli (in Frankliniella occidentalis ocellar setae III are about as long as distance between external margins of hind ocelli, and in Frankliniella borinquen as long as distance between midpoints of hind ocelli). In Frankliniella borinquen as well as Frankliniella schultzei the length of postocular setae IV are about as long as distance between hind ocelli (in Frankliniella occidentalis postocular setae IV are longer and in Frankliniella williamsi distinctly shorter than distance between hind ocelli). Compared to Frankliniella williamsi which has 1 or 2 median discal setae in addition to marginal setae on sternite II, in other species of Frankliniella sternite II without median discal setae.
Species of the genus Frankliniella are similar to species of Thrips, Stenchaetothrips, Microcephalothrips abdominalis, Larothrips dentipes and Fulmekiola serrata, in having tergites V-VIII which bear a pair of ctenidia laterally, but in those species ctenidia of the tergite VIII lie posteromedial to the spiracle, whereas species of Frankliniella have ctenidia on tergite VIII which lie anterolateral to the spiracle.

Life history
Life cycle usually takes about 2-5 weeks (Hill 1983); with eggs hatch in 5-8 days, nymphs undergo 3 instars in 8-10 days, pupation lasts 4-7 days (Gahukar 2004). On tomato the embryonic period lasts 4.3 d; the 1st instar 2.5 d; the 2nd instar 2.5 d; prepupa 1.2 d; pupa 2.1 d; duration of the immature phase 8.3 d; male longevity lasts 13.1 and female longevity 13.6 d. The life cycle duration takes 12.6 d (Pinent and Carvalho, 1998).

Host plants
Polyphagous and flower feeding; compositae crops and weeds.
Crops: African nightshade, African spiderplant, amaranth, babycorn, beans (broad bean, common bean, cowpea, French bean, garden pea, hyacinth bean, Lima bean), beet root, brocolli, cabbage, capsicum, cassava, chillies, coriander, cotton, courgette, cucurbit, eggplant, green gram, groundnut, leek, kale, maize, okra, onion, potato, pumpkin, red gram, sorghum, sunflower, sweet potato, thorn apple, tobacco, tomato, watermelon, wheat.
Weeds: Achyranthes aspera, Ajuga remota, Bidens pilosa, Chenopodium sp., Conyza bonariensis, Crotolaria sp., Datura suaveolens, Dyschoriste radicans, Erlangea calycina, Galinsoga parviflora, Guizotia scabra, Hermannia oliveri,Lantana camara, Malvaviscus grandiflorus, Melhania velutina, Nicandra physalodes, Sesbania sesban, Solanum incanum, Sonchus oleraceus, Tagetes minuta, Tithonia diversifolia.

Vector capacity
Capsicum chlorosis virus (CaCV)
Chrysanthemum stem necrosis virus(CSNV)
Groundnut ringspot virus (GRSV)
Impatiens necrotic spot virus (INSV)
Tomato chlorotic spot virus TCSV)
Tomato spotted wilt virus (TSWV)
Also known to carry spores, mildews, rusts and other fungi.
The dark forms of Franklinella schultzei are competent vectors of the above five tospoviruses, however the pale forms are not competent virus vectors (Sakimura 1969; Whitfield et al. 2005, Reitz et al. 2011).

Damage and symptoms
The species breeds on the flowers and leaves and damages young leaves within the meristematic bud. They rasp the cells off the upper surface of young leaves, while they are still in the bud (Hill 1983). Silvery scars appear on the upper surface of leaves and those leaves distorted. Adults prefer young leaves and flowers, nymphs leaf buds (Gahukar 2004).

Detection and control strategies
Frankliniella schultzei are attracted to both yellow and blue sticky traps, which could be used for effective monitoring of their dynamics in the field. Further their attraction to coloured sticky traps is enhanced by flower based kairomones (Muvea, 2011).
Intercropping of cowpea with pearl millet under different configurations significantly reduced the abundance of Frankliniella schultzei (Gahukar 1989). Frankliniella schultzei was highly attracted to Irish Potato intercropped with French beans (Nyasani et al. 2012). In Senegal, cowpea and wild groundnut, Arachis diogoi, showed tolerance to pest attack (Gahukar 1987). The Australian phytoseiid mite Typhlodromips montdorensis (Acari: Phytoseiidae) has a daily consumption rate of 10.63 first-instar thrips larvae of Frankliniella schultzei (Steiner et al. 2003).

Biogeography

Tropical to subtropical and southern Mediterranean, Africa, Asia, Australia, New Zealand, Central and South America, North America. Angola, Benin, Botswana, Burkina Faso, Cameroon, Cape Verde, Central African Republic, Chad, Congo (Brazzaville), Egypt (Maadi), Ethiopia, Gabon, Gambia (Abuko, Kombo), Ghana (Aburi), Kenya, Libya, Madagascar, Maurititius, Morocco, Niger, Nigeria, Namibia, Senegal, Somalia, South Africa (Eastern Cape: Somerset East; Western Cape: Somerset West; Prince Albert Road), Sudan, Tanzania, Tunisia, Togo (Wonugba), Uganda, Zambia, Zimbabwe.

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