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Aphids on dogwood (Cornus)

Species Overview: Anoecia corni  Aphis salicariae  Species of dogwood 

Aphids on dogwood

Blackman & Eastop list about 30 species of aphids  as feeding on dogwoods worldwide, and provides formal identification keys for aphids on Cornus. Most of the aphids are in the genera Anoecia  and Aphis,  with a few Macrosiphum  species and even fewer polyphagous species. Most Anoecia species are restricted to North America.

In rough order of abundance, we cover two aphid species found on two of the species of dogwood in Europe (the common dogwood, Cornus sanguinea, and the red-barked dogwood, Cornus alba). Assistance on identifying these two species of dogwood is below. 

 

Anoecia corni (Common dogwood-grass aphid)

The apterous fundatrices (see first picture below) in spring on dogwood (Cornus) are dark brown or blackish. The siphunculi of all Anoecia corni forms are reduced to inconspicuous pores. The winged form (see second picture below) has a large black pterostigmal spot on the forewing, a white band around the top of the abdomen and a dark patch on the abdomen covering tergites 3-6. The body length of winged forms is quite variable ranging from 1.9-3.0 mm.

 

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.

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Aphis salicariae (Dogwood - rosebay willowherb aphid)

The apterae are reddish brown with a marked wax bloom making the aphids appear pinkish. The dorsal abdominal sclerotic pattern comprises variably complete transverse bands across tergites 6-8 and several other small sclerites. The siphunculi are gently to rather strongly curved outwards, and the cauda is short and bluntly tapering (see first picture below). The body length of apterae is 1.8-2.3 mm. The ovipara (see second picture below) has an elongated abdomen and rather strongly swollen hind tibiae.

 

The dogwood - rosebay willowherb aphid host alternates between dogwood (Cornus alba) where it feeds in developing flower umbels and rosebay willowherb (Epilobium angustifolium) where it lives in colonies along the midribs of the underside of the leaves (see picture below).

In autumn there is a return migration to dogwood where sexual forms develop, and the oviparae lay the overwintering eggs. It is widely distributed through Europe into north-west and central Asia.

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Species of dogwood

We cover two species of dogwood, common dogwood (Cornus sanguinea) and red-barked dogwood (Cornus alba). Common dogwood 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), 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.

Acknowledgements

We have made provisional identifications from high resolution photos of living specimens, along with host plant identity. In the great majority of cases, identifications have been confirmed by microscopic examination of preserved specimens. We have used the keys and species accounts of Blackman & Eastop (1994)  and Blackman & Eastop (2006)  supplemented with Blackman (1974) , Stroyan (1977) , Stroyan (1984) , Blackman & Eastop (1984) , Heie (1980-1995) , Dixon & Thieme (2007)  and Blackman (2010) . We fully acknowledge these authors 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

  •  Blackman, R.L. & Eastop, V.F. Aphids on the world's plants An online identification and information guide. Full text