Heliothrips sylvanus Faure, 1933

Panchaetothripinae, Thripidae, Terebrantia, Thysanoptera

Figures

Fig. 1: 8-segmented antenna
Fig. 2: Head dorsal with ocellar triangle
Fig. 3: Head and pronotum
Fig. 4: Pro- and mesonotum
Fig. 5: Meso- and metanotum
Fig. 6: Fore wing and fore wing apical region
Fig. 7: Tergites IV-VI
Fig. 8: Tergites VI-VIII
Fig. 9: Sternites IV-VI
Fig. 10: Tergites IX and X
Fig. 11: Tergites VIII-X, male

Heliothrips sylvanus causes damage on leaves of avocado, grapes, guava and persimmon. Both sexes fully winged. Body, legs and antennal segments I & II dark brown; antennal segment III basally, VI apically and VII and VIII brown; III apically, IV and V and VI basally pale; fore wings pale with hind margin shaded. Antennae 8-segmented; segments III and IV with sense cone simple; VIII at least 3 times as long as VII (Fig. 1). Head as long as wide, strongly reticulate, cheeks parallel and constricted at base (Fig. 2). Pronotum reticulate, with no long setae (Fig. 3). Mesonotum with an incomplete median division (Fig. 4). Metanotum with strongly reticulate triangle; median setae small on anterior half of sclerite (Fig. 5). Mid and hind tarsi short and 1-segmented. Fore wing slender with apex rounded bearing 2 long cilia; fore wing first vein close to or fused to costal vein, costa without long cilia, posteromarginal cilia not wavy; veinal setae not much larger than surface microtrichia (Fig. 6). Tergites covered by large hexagonal reticulations except for a pair of posterior submedian smooth areas; tergites II-VIII with 1 pair of small setae medially (Fig. 7); VIII with posteromarginal comb of short microtrichia on broadly triangular bases (Fig. 8); X short but with complete median division (Fig. 10). Sternites with 3 pairs of small marginal setae (Fig. 9).
Male similar to female; tergite IX with 3 pairs of stout thorn-like setae (Fig. 11); sternites III-VII each with a large kidney-shaped transverse glandular area.

The genus Heliothrips Haliday, 1836
There are 4 species within this genus, one of each from South Africa, Indonesia and South America, and the greenhouse thrips, Heliothrips haemorrhoidalis, that is now distributed worldwide (Mound & Kibby 1998). All of the species are flattened dorso-ventrally and show heavy reticulation. The head is covered with polygonal reticulations and has a constricted neck, antennae are 8-segmented, antennal segments III & IV have a simple sense cone, fore wings have straight cilia on the posterior margin, minute setae on veins, and a rounded apex and a swollen base (Mound & Marullo 1996; Wilson 1975).

The species is similar to Heliothrips haemorrhoidalis that differs from Heliothrips sylvanus by the presence of distinct fringe cilia on anterior margin of fore wings, having cheeks on head slightly concave and legs entirely pale, head wider than long, median setal pair of tergites longer than distance between their bases, and tergite VIII has a posteromarginal comb of laterally long and slender microtrichia (Heliothrips sylvanus without fringe cilia on anterior margin of fore wings, cheeks are parallel and legs entirely dark brown, the head is about as long as wide, median setal pair of tergites shorter than distance between their bases, and tergite VIII with a posteromarginal comb of short microtrichia).
Heliothrips is one of several small genera of Panchaetothripinae in which the species have slender fore wings with very short major setae and straight posteromarginal cilia without undulations, like in Phibalothrips, Retithrips and Rhipiphorothrips. Compared to Phibalothrips peringueyi, the species of Heliothrips have 8-segmented antennae and mostly a complete comb of posteromarginal microtrichia on tergite VIII (Phibalothrips peringueyi with 7-segmented antennae and incomplete comb of microtrichia on tergite VIII). Retithrips syriacus differs from others in having a reticulate sculpture that bears internal markings, shape of metathoracic furca elongate and Y-shaped, fore wings bearing anteromarginally 3 curious blister-like callosities, and minute setae on tergite X. Rhipiphorothrips miemsae differs from species of Heliothrips in bearing a strong irregular reticulate and rugose sculpture on head and pronotum. Furthermore, Retithrips as well as Rhipiphorothrips have a forked sense cone on antennal segments III & IV (Heliothrips and Phibalothrips with simple sense cone on antennal segments III and IV).

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
Avocado, grapes, guava, sweet and astringent persimmon.

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

Damage and symptoms
Adults and larvae prefer the abaxial surface of mature leaves of vines and causes silvering or bronzing of foliage (Childers 1997; Schwartz 1989). As well as Heliothrips haemorrhoidalis, adults, larvae and pupae of Heliothrips sylvanus primarily feed on the underside of leaves. Leaves become distorted, curled under, silvered or bronzed and covered by black spots on the undersides (Allsopp 2009).

Detection and control strategies
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Additional notes
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Biogeography

South Africa (Limpopo: Woodbush; Western Cape: Mossel Bay; KwaZulu-Natal; Eastern Cape).

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Schwartz A (1989). The incidence of Heliothrips sylvanus Faure (Thysanoptera: Thripidae) on table grapes. South African Journal of Enology and Viticulture. 10 (2): 59-61

Wilson TH (1975). A monograph of the subfamily Panchaetothripinae (Thysanoptera: Thripidae). Memoirs of the American Entomological Institute. 23: 1-354

zur Strassen R (1960). Catalogue of the known species of South African Thysanoptera. Journal of the Entomological Society of Southern Africa. 23 (2): 321-367

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