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Aphidinae : Macrosiphini : Sitobion luteum
 

 

Sitobion luteum

Yellow orchid aphid

On this page: Identification & Distribution Other aphids on the same host Damage & Control

Identification & Distribution

Adult apterae of Sitobion luteum (see foreground of first picture below) are bright yellow to pale yellowish green, with a large black oval sclerotic area extending over tergites I-V, with only small marginal indentations (cf. Sitobion indicum, which has a dorsal abdominal patch with a very irregular outline and large intersegmental indentations). There is a narrow cross bar on the metathorax (the hind thoracic segment), small marginal spots on tergites I-IV, and rather large postsiphuncular sclerites. The antennal tubercles are well developed, with the median frontal tubercle distinct but rather small. Antennae are black except at the bases and bear 1-4 secondary rhinaria on segment III. They are 1.2-1.5 times the body length, with the terminal process about 5.5 times the base of antennal segment VI. Antennal hairs on segment III are 0.3-0.4 times the basal diameter of that segment. The apical rostral segment (RIV+V) is slightly longer than the second hind tarsal segment (HTII). The siphunculi are black and rather thick, 1.4-2.0 times the length of the yellow cauda with reticulation on the apical part (cf. Sitobion orchidacearum, which has siphunculi 1.1-1.3 times the caudal length). The cauda is not constricted, rather pointed, with 6-8 hairs (cf. Sitobion indicum, which has 9-13 hairs on the cauda). The body length of adult apterae is 1.3-2.4 mm. Immature Sitobion luteum are similar to the adult aptera, with yellow body and black siphunculi, but they lack the black sclerotic patch on the dorsum.

First image above copyright Rolf Lawrenz, second image copyright Tamiranda,
both under a creative commons licence.

The alate Sitobion luteum (not pictured) has the head and thorax rather dark, and the abdomen yellow with dark narrow intersegmental markings instead of a patch. Antennal segment III bears 10-19 rather large secondary rhinaria. The siphunculi are slightly shorter than in the apterous vivipara. The cauda is more or less constricted with 7-9 hairs. The body length of the alate is about 2.3 mm.

The yellow orchid aphid feeds on a wide range of orchid genera (including Dendrobium, Epidendrum, Laelia, Oncidium). It appears to be wholly anholocyclic, no sexual morphs having been recorded. Sitobion luteum has a world-wide distribution including Madagascar, Mauritius, India, Singapore, Java, New Guinea, Australia, Fiji, Tahiti, central and South America, and under glass in Europe and USA.

 

Other aphids on the same host

Sitobion luteum has been recorded on 9 Dendrobium species (Dendrobium aemulum, Dendrobium bigibbum, Dendrobium densiflorum, Dendrobium heterocarpum, Dendrobium jonesii, Dendrobium kingianum, Dendrobium longicornu, Dendrobium moschatum, Dendrobium mutabile).

Sitobion luteum has been recorded on 2 Epidendrum species (Epidendrum diforme, Epidendrum ellipticum).

 

Damage and control

On orchids aphids are found feeding on the buds and flowers, and also on other succulent new and growing tissues such as the leaves, sheaths, and flower parts. Plant damage is done by repeated insertion and probing, as well as by nutrient removal. Feeding debilitates the plant and can cause generalized yellowing, and distorted leaves and flowers. As well as direct feeding damage, aphids can also transmit plant viruses, although this is not thought to be a serious problem for orchids. A wide range of insecticides are available for aphid control, but where conditions are manipulated as in greenhouses, biological or integrated control offer the best options. For more on controlling aphids on orchids see St Augustine Orchid Society.

Acknowledgements

We are very grateful to Rolf Lawrenz and Tamiranda for making their pictures of Sitobion luteum available for use under a creative commons licence.

Identification was done by the photographers credited above. We have used the species account of Hille Ris Lambers (1939) (as Macrosiphum luteum), and Heie (1980-1995), along with information from Roger Blackman & Victor Eastop in Aphids on Worlds Plants. We fully acknowledge these authors and those listed in the reference sections as the source for the (summarized) taxonomic information we have presented. Any errors in identification or information are ours alone, and we would be very grateful for any corrections. For assistance on the terms used for aphid morphology we suggest the figure provided by Blackman & Eastop (2006).

Useful weblinks

References

  • Hille Ris Lambers, D. (1939). Contributions to a monograph of the Aphididae of Europe II. The genera Dactynotus Rafinesque, 1818; Staticobium Mordvilko, 1914; Macrosiphum Passserini, 1860; Masonaphis nov.gen.; Pharalis Leach, 18256. Temminckia 4, 1-134 (p 118) Abstract