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Poplar shoot aphidOn this page: Identification & Distribution Biology & Ecology: Life cycle Colour Ant attendance Other aphids on the same host Damage & Control
Identification & Distribution
Adult Chaitophorus populeti apterae are oval in shape and most commonly shiny dark green to black (see first picture below) (cf. Chaitophorus populialbae, which are pale greenish to yellowish white with no dark markings). The antennae are more than half the length of the body. The terminal process is about twice the length of the base of the last antennal segment. The dorsum of the aptera is dark sclerotic, usually forming a more or less solid dark carapace from abdominal tergites I to VI inclusive, but sometimes with a paler median area on tergites I-II (see second picture below). There are separate bands on the pro- and mesonotum and on abdominal tergites VII-VIII. Chaitophorus populeti has a small number of pseudosensoria on the hind tibiae of the adult vivipara (cf. Chaitophorus leucomelas and Chaitophorus tremulae viviparae, which do not have any pseudosensoria on the hind tibiae).The siphunculi are dark. The body length of Chaitophorus populeti is 1.5-2.9 mm.
Chaitophorus populeti alates (see second picture above) are dark green to black with broad brown dorsal abdominal cross-bands and marginal plates. The wing veins are brown-shadowed.
The micrographs below show two adult apterae and an alate, dorsal in alcohol.
The poplar shoot aphid lives on the young shoots and terminal leaf petioles of various poplar (Populus) species, especially of the aspen (Populus tremula) and white poplar (Populus alba). It is usually attended by ants. Oviparae and males occur in October-November. Chaitophorus populeti is found throughout the Palaearctic region.
Biology & Ecology
Chaitophorus populeti is the commonest stem-feeder in the genus and feeds on several species of poplar and on aspen. The species overwinters in the egg stage. The fundatrices hatch in spring and reproduce parthenogenetically through spring and summer. Sexual forms are usually produced in October, and can be found rather more easily than with most aphid species. The males are small, dark and apterous (see pictures below), with secondary rhinaria on antennal joints III-V inclusive.
The oviparae (see picture below) are somewhat larger than the apterous viviparae, with a membranous dorsum apart from bands across pronotum and abdominal tergite 8 (rarely also 7). Tergite 8 and the subgenital plate have more hairs than in corresponding apterous viviparae.
They can be found sitting alone on small branches late into the year, mumbling obscure imprecations whilst peering through horn rimmed spectacles at their knitting.
There are several different colour forms of the nymphs, the commonest of which are green and reddish-brown.
The first image shows two adult apterae with greenish nymphs. The second image above shows a reddish alate with similarly coloured nymphs. The dorsal pattern on the nymphs remains constant irrespective of the background color.
The most dramatic colour form we have encountered is the golden-yellow form shown below.
Most of the aphids on just one aspen sucker were yellow patterned with gold.
The functional significance of this colour polymorphism is unknown.
The poplar shoot aphid is nearly always attended by (and vigorously defended by) ants, including various species of Formica, Lasius and Myrmica. The two images below show poplar shoot aphid being attended by southern wood ants (Formica rufa). The second image shows a Formica rufa in full defensive posture, with mandibles open wide and abdomen swung forward ready to spray a mixture of formic acid and gland secretions into any potential attacker.
Novgodorova (2005) carried out an experimental study on attendance of Chaitophorus populeti by several species of ants including red wood ants (Formica) and black ants (Lasius). He placed adult and larval ladybirds (Coccinella septempunctata) in Chaitophorus populeti colonies and showed that only ants with large protected territories (such as wood ants) attacked both adult and larval predators. Other species of ants (such as black ants) either protected aphids only from adult ladybirds, or did not guard them at all. Wood ants only killed myrmecophilous (ant-associated) aphids if they were left unattended or were injured.
The first image above shows a colony attended by Lasius ants, whilst the second shows a colony attended by Myrmica rubra. Honeydew sugar composition plays an important role in ant-aphid interactions, with ants responding most intensively to honeydew containing high amounts of the sugar melezitose. Fischer & Shingleton (2001) have shown that Chaitophorus populeti (and Chaitophorus populialbae) are able to modify the melezitose content of their honeydew, reducing it when there are no ants available to attend them. This is probably because maintaining a high content is costly for aphids since they have to feed faster and increase the rate of converting simple to complex sugars.
Sometimes very large Chaitophorus populeti colonies develop, and the ants may not be able to remove all the accumulated honeydew. In these circumstances other honeydew feeders may aggregate in the area, including wasps and various species of Diptera. The picture above shows one such fly feeding off the honeydew in the colony.
Other aphids on same host:
Chaitophorus populeti has been recorded from 21 Populus species.
Blackman & Eastop list about 120 species of aphids as feeding on Populus (poplar and aspen species) worldwide.
Damage and control
The poplar shoot aphid does not usually seem to be regarded as an important pest other than in relation to honeydew production on ornamental trees. However, Sadeqi et al. (2007) mention it as one of the more important pests of poplars in Iran where poplar is grown both for wood and as shade trees in urban ecosystems. Also in Iran Mojib et al. (2002) investigated the coccinellid predator Oenopia conglobata as a possible contributor to an integrated control package for poplar pests such as Chaitophorus populeti.