Sitobion fragariae

Identification & Distribution:

The Sitobion fragariae aptera is dirty yellowish green (see first picture below), with small brown intersegmental sclerites on the abdominal dorsum. The antennae are about the same length as the body, with the basal segments paler than the rest. The siphunculi are usually entirely black, although they may have paler bases on the primary host. They are 1.8-2.7 times longer than the pale pointed cauda (on blackberry cf. Macrosiphum funestum, which has the siphunculi 2.5-3.5 times the length of the cauda; on grass cf. Sitobion avenae, which has the siphunculi 1.1-1.5 times the length of the cauda). The body length of Sitobion fragariae apterae is 1.6-3.0 mm long.

The clarified slide mounts below are of adult viviparous female Sitobion fragariae on the secondary host (grasses): wingless, and winged.

The blackberry - grass aphid host alternates from blackberry (Rubus fruticosus agg.) and occasionally other Rosaceae to grasses (Poaceae) especially Holcus spp. and some sedges (Carex spp). Sitobion fragariae eggs hatch in spring and the young nymphs feed on the breaking buds. Colonies build up and in summer alates migrate to cereals and grasses. A return migration takes place in autumn.

Other aphids on same host:

Primary hosts

Sitobion fragariae has been recorded from 11 Rubus species.

• Blackman & Eastop list 10 species of aphid as feeding on blackberry (Rubus fruticosus) worldwide, and provide formal identification keys (Show World list).

  Of those aphid species, Baker (2015) lists 7 as occurring in Britain (Show British list).

Secondary hosts:

• Sitobion fragariae has been recorded from 3 Holcus species (Holcus annuus, Holcus lanatus, Holcus mollis).

  Blackman & Eastop list 23 species of aphid as feeding on 'Yorkshire fog' (Holcus lanatus) worldwide, and provide formal identification keys (Show World list).

  Of those aphid species, Baker (2015) lists 22 as occurring in Britain (Show British list).

• Blackman & Eastop list 11 species of aphid as feeding on 'creeping soft grass' (Holcus mollis) worldwide, and provide formal identification keys (Show World list).

  Of those aphid species, Baker (2015) lists all 11 as occurring in Britain (Show British list).

• Sitobion fragariae has been recorded from 17 Carex species.

  Blackman & Eastop list about 110 species of aphids as feeding on sedges worldwide, and provide formal identification keys for aphids on Carex (Show World list).

  Of those, Baker (2015) lists 32 aphid species as occurring in Britain (Show British list).

Acknowledgements Our particular thanks to Roger Blackman for images of his clarified slide mounts. Whilst we make every effort to ensure that identifications are correct, we cannot absolutely warranty their accuracy. We have mostly made 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

 

Identification requests David Fenwick, 10 June 14 Have an interesting aphid for you, what appears to be a Sitobion. It was found on Wall Barley, Hordeum murinum, on a small pier at Newlyn today. 10.06.14. SW 46490 28497. Juveniles quite orange in colour. Few adults, mostly juveniles on each inflorescence, grass also looked like it was going over, becoming dry and purplish. Hope I have the right genus. Image(s) copyright www.aphotofauna.com all rights reserved.     ... Think I have it, Sitobion avenae! A variable little beastie! Bob, InfluentialPoints: I know it can be rather variable, but I'm not convinced it is Sitobian avenae. Even allowing for foreshortening due to perspective, the siphunculi are too long relative to the cauda. (S. avenae siphunculi are no more than 1.4 times the length of the cauda.) Given the host and the dark siphunculi, it is much more likely to be Sitobion fragariae, whose siphunculi are at least twice the length of the cauda.