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Aphids on dogwood (Cornus)On this page: Species lists Anoecia corni Aphis salicariae Species of dogwoodAphids on dogwoodBlackman & Eastop list about 30 species of aphids as feeding on dogwoods worldwide, and provides formal identification keys for aphids on Cornus. Those species feeding on common dogwood (Cornus sanguinea), and red-barked dogwood (Cornus alba) that are found in Britain are listed below in alphabetical order.
Below we show pictures and identification characteristics of most of these aphid species roughly in order of abundance with the commonest first. Assistance on identifying these two species of dogwood is below. Anoecia corni (Common dogwood-grass aphid)Anoecia corni apterous fundatrices in spring on dogwood (Cornus) are dark brown or blackish (see first picture below). They have reduced eyes and 5-segmented antennae, whereas subsequent generations have large compound eyes and 6-segmented antennae. The siphunculi of all Anoecia corni forms are reduced to inconspicuous pores. Winged forms, both spring migrants and the sexuparae returning to Cornus in autumn (see second picture below), have a large black pterostigmal spot on the forewing, and a white band bordering the dark patch on abdominal tergites III-VI (cf. Anoecia vagans which has no dark dorsal abdominal patch).
It is difficult to separate the apterae of Anoecia corni from two other Anoecia species that (may) occur on dogwood, but the alates may be distinguished by examining their antennae. The 5th and 6th antennal segments of Anoecia corni alates both have secondary rhinaria (c.f. Anoecia vagans which has none on those segments). The third antennal segment of Anoecia corni has 9-17 secondary rhinaria (c.f. Anoecia major which has 13-22 secondary rhinaria on that segment). The body length of winged forms is quite variable, ranging from 1.9-3.0 mm. The third picture above shows a colony of Anoecia corni on its secondary host - roots of grasses, attended by the common black ant Lasius niger. In Europe Anoecia corni host alternates between dogwood (Cornus spp.) and roots of grasses (Poaceae). In eastern Asia and in areas where introduced (South Africa and North America), the dogwood-grass aphid remains all year round on grasses and some cereals. The species is found throughout Europe, and in Asia, Africa, and North and South America. Aphis salicariae (Dogwood - rosebay willowherb aphid)Aphis salicariae apterae are reddish brown with a marked wax bloom. The wax coating is heavier on the primary host making the aphids appear grey (see first picture below), but lighter on the secondary host so the aphids appear pinkish (see second picture below). The mid-dorsum of the Aphis salicariae aptera is more or less membranous but there are small postsiphuncular and marginal sclerites, dark intersegmental muscle sclerites and transverse bands across tergites 6-8. The siphunculi are gently to rather strongly curved outwards, and the cauda is short and bluntly tapering. The body length of Aphis salicariae apterae is 1.8-2.3 mm.
The alate Aphis salicariae (see third picture above) is much less heavily waxed than the aptera, and has a better developed pattern with larger marginals and postsiphunculars and short median sclerites on most of the tergites. As with the aptera, the siphunculi are curved outwards. The primary host of the dogwood - rosebay willowherb aphid host is the red-barked dogwood (Cornus alba) where the aphid causes leaf curl and feeds in developing flower umbels. The secondary host is rosebay willowherb (Chamaenerion (=Epilobium) angustifolium) where the aphid lives in colonies along the midribs of the underside of the leaves. It is often attended by ants. Sexual forms occur in autumn. Aphis salicariae is widely distributed through Europe into north-west and central Asia, and has been introduced to and is widepread in North America. Species of dogwoodWe cover two species of dogwood, common dogwood (Cornus sanguinea) and red-barked dogwood (Cornus alba). Common dogwood (see first picture below) is native to Europe and western Asia. It is a medium-sized shrub with reddish twigs and green ovate to oblong leaves . The flowers are small with four creamy white petals, and are in clusters 3-5 cm diameter. The fruit is a globose black berry.
The variegated cultivar 'elegantissima' of the red-barked dogwood (Cornus alba) (see second picture above), native to China, is popularly grown in gardens as an ornamental. It is a bushy deciduous medium sized shrub up to 3 m, with deep red stems and grey-green, white-margined narrowly ovate leaves up to 10 cm in length. The flowers are small and creamy white in flat heads. The fruit is a globose white berry.
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