Parthenothrips dracaenae (Heeger, 1854)

Panchaetothripinae, Thripidae, Terebrantia, Thysanoptera

Figures

Fig. 1: 7-segmented antenna, pedicel, segments III and IV with simple sense cone, terminal segments V-VII
Fig. 2: Head dorsal with ocellar triangle
Fig. 3: Head dorsal with ocellar triangle
Fig. 4: Pronotum
Fig. 5: Meso- and metanotum
Fig. 6: Meso- and metasternum
Fig. 7: Fore wing and fore wing basal region
Fig. 8: Sternite VII
Fig. 9: Tergites VII and VIII
Fig. 10: Tergites IX-XI
Fig. 11: Adult female feeding on a gum tree leaf

Parthenothrips dracaenae breeds on a wide range of plants, particularly on leaves of the native african succulent shrub Dracaena sp. and Kentia palm (Howea sp). Both sexes fully winged. Body light brown to brown; tarsi and tibiae yellow, also antennal segments I-V; fore wings pale, with small dark cross band in basal half (where first vein fuses to costa) and a more diffuse shaded area on distal half (Fig. 11). Antennae 7-segmented; sense cone on segments III & IV short and simple, VII almost as long as previous segment (Fig. 1). Head reticulate; cheeks parallel sided but constricted to basal neck; vertex with 2 pairs of large but translucent flattened setae (Fig. 2 and 3). Pronotum with 1 pair of large, flattened posteroangular setae; discal area and posterior margin with similar but smaller setae (Fig. 4). Mesonotum not divided medially. Metanotum with median area reticulate; with 1 pair of setae medially and 1 pair of campaniform sensilla (Fig. 5); metafurca elongate and Y-shaped (Fig. 6). Mid and hind tarsi 1-segmented. Fore wing first vein close to or fused to costal vein, fore wing exceptionally broad with constriction in basal third and reticulate membrane; veinal setae broad with thickened median rhachis; costa without cilia; posteromarginal cilia wavy (Fig. 7). Tergites and sternites with broad craspedum; tergites without reticulation medially and weak reticulation laterally, median setae small (Fig. 8 and 9); tergite X with complete median division (Fig. 10). Sternites with 3 pairs of small marginal setae.
Male similar to female but smaller; tergite IX with no strong setae; sternites IV-VII with transverse oblong glandular area, larger on posterior sternites.

The genus Parthenothrips Uzel, 1895
There is only one species in this genus. The palm thrips, Parthenothrips dracaenae, is widespread throughout the tropics, and is common on indoor ornamental plants in temperate regions (Mound & Kibby 1998). The body is golden brown with heavy sculpture on the head, legs, thorax and wings. The fore wings are highly distinctive, broad with the reticulate surface pale with one dark band in the basal half and one small shaded area distally, unique amongst all Thripidae.

The broad, reticulate fore wings that lack fringe cilia on the anterior margin, and the remarkable quill-like major setae on the wings (flattened with prominent rhachis), are highly distinctive of the genus Parthenothrips. Only Retithrips syriacus has wide fore wings but without reticulations and with prominent callosities between costa and anterior vein which is lacking in Parthenothrips.

Life history
As with other thrips species the life cycle from egg to adult is dependent on temperature. The full cycle can take about 7 days in a greenhouse and 15 days to over a month in outdoor populations and adults may live for more than one month producing several generations in one year depending on seasonal weather (Lewis 1973).

Host plants
Dracaena sp. (Australian palm), Ficus elastica, Howea sp. (Kentia palm) and ornamentals (orchids) in greenhouses.

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

Damage and symptoms
Larvae and adults feed on mature leaves rather than young leaves, and pupae also occur on leaves. Feeding on a wide range of plants, most of which have hard leaves. Palm thrips causes typical direct damage on leaves of host plants - silver areas that violate aesthetic appearance of ornamental plants (Trdan et al. 2005).

Detection and control strategies
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Additional notes
When found this thrips is slow moving sometimes requiring prodding with a fine paint brush to stimulate flight.
Palm thrips is the first species from the Thysanoptera order that was found to be capable for thelytokous parthenogenetic reproduction. This characteristics is contained in the latin name of the genus. Populations are almost completely composed of females at the temperatures from 25-28°C, while a few males can be found at the lower temperatures (18-20°C) (Lewis 1973).

Biogeography

Worldwide distributed in greenhouses on ornamental plants and found in outdoor populations in the tropics and subtropics. South Africa (KwaZulu-Natal: Durban; Western Cape: Wynberg).

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