Diarthrothrips coffeae Williams, 1915

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 ventral with mouthcone
Fig. 4: Pronotum
Fig. 5: Meso- and metanotum
Fig. 6: Meso- and metasternum with furca and spinula
Fig. 7: Fore wing, apex region of fore wing
Fig. 8: Tergites IV-VI
Fig. 9: Sternites II-IV
Fig. 10: Sternites VI and VII
Fig. 11: Tergites IX and X
Fig. 12: Tergites VIII-XI

Diarthrothrips coffeae attacks leaves, twigs and berries of Arabica coffee in East Africa. Both sexes fully winged. Body pale to dark brown; abdomen, except for the last three segments, a little darker; antennae rather darker than the body with apex of segments III & IV and base of segment V paler, segments IV & V with a more or less clear ring near the base which separated off narrow darker ring at the base; legs paler than the body; fore wings pale yellowish with 2, sometimes indistinct, small dark areas - one at the base of second vein and another in the posterior half of fore wing. Antennae 8-segmented; segments III & IV with slender forked sensorium (Fig. 1). Head about as long as wide; 3 pairs of ocellar setae, pair I quite short, II & III long and slender, pair III arise within ocellar triangle anterior to tangent of anterior margin of hind ocelli (Fig. 2 and 3). Pronotum not reticulate; with 2 pairs of elongate posteroangular setae (Fig. 4). Metanotum median area weakly sculptured; median setae small and arising well behind anterior margin (Fig. 5). Meso- and metafurca with median spinula (Fig. 6). Mid and hind tarsi 2-segmented. Fore wing first vein with a long gap in setal row, 5 setae basally and 2 distally; second vein with complete row of 12-16 setae (Fig. 7). Tergites with median pair of setae shorter than distance between their bases (Fig. 8); posterior margin of VIII without a comb of microtrichia (Fig. 11); tergite X with no longitudinal split (Fig. 12). Sternites without discal setae; long median setae on sternite VII arising in front of hind margin (Fig. 9).
Male paler and smaller than female; without glandular areas.

The genus Diarthrothrips Williams, 1915
There are only 2 species in this genus, one from India and another from East and West Africa. Both have 8-segmented antennae, antennal segments III & IV with slender forked sense cone, antennal segments IV & V with a clear ring near the base which separated off narrow darker ring at the base, 3 pairs of ocellar setae on head, 2 pairs of elongate posteroangular pronotal setae, and the meso- and metathorax with a well developed internal spinula.

Diarthrothrips coffeae is similar to Chirothrips guillarmodi, Scolothrips rhagebianus and species of Craspedothrips in having 8-segmented antennae with forked sense cone on segments III and IV, 2 pairs of elongate posteroangular pronotal setae, lateral thirds of tergites without regular rows of fine microtrichia, and tergite VIII without paired ctenidia laterally and without posteromarginal comb of microtrichia. But Chirothrips guillarmodi has a trapezoidal pronotum, and the meso- and metafurca are without median spinula. Scolothrips rhagebianus possesses altogether 6 pairs of elongate pronotal setae, and fore wing costal setae at middle of wing are about twice or more as long as median wing width. And species of Craspedothrips have the metasternal furca without median spinula.

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

Host plants
Coffee (Coffea arabica).

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

Damage and symptoms
Attacks especially under sides of leaves, and in severe cases the upper sides of leaves, berries and green shoots, with irregular grey or silvery patches covered by minute black spots. Death of leaves and total leaf-fall may follow a very heavy infestation (Hill 1983).

Detection and control strategies
Control by mulching the coffee trees with elephant grass and application of dicrotophos, fenitrothion or parathion (Kranz et al. 1977).
Mulching with a suitable material, such as banana leaves or cut dried grass, may help to improve soil conditions by increasing soil fertility, reducing soil acidity, conserving soil moisture and protecting the soil from compaction and surface erosion due to run-off water. Mulching can also have a direct effect on pest population. It appears that populations of coffee thrips, which thrive under hot, dry conditions, are reduced in the cooler, humid conditions of a mulched field (Magina 2005).
Mulching reduces thrips numbers considerably and its widespread use in recent years is probably a reason for the declining importance of this pest. Non-persistent insecticides such a fenitrothion and fenithion give effective thrips control for only a few days after spraying. DDT or dieldrin were used earlier for their management, despite the risk of causing outbreaks of other pests (Hill 1983).

Additional notes
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Biogeography

East Africa. Congo, Kenya (Kabete), Malawi, Tanzania, Uganda.

Hill D (1983). Agricultural insect pests of the tropics and their control, (2nd edition). Cambridge University Press, Cambridge, 746 pp

Kranz J, Schmutterer H & Koch W (1977). Diseases, pests and weeds in tropical crops. Paul Parey, Berlin & Hamburg, 666 pp

le Pelley RH (1969). Pests of coffee. Tropical Science Series. Longmans, London, 590 pp

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

Magina FL (2005). A review of coffe pest managment. Tanzania Coffee Research Institute, Lyamungu, 39 pp

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

Williams CB (1915). A new thrips damaging coffee in British East Africa. Bulletin of Entomological Research. 6: 269-272