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Acyrthosiphon malvae

Geranium aphid, Pelargonium aphid

On this page: Identification & Distribution Biology & Ecology Other aphids on the same host

Identification & Distribution:

Acyrthosiphon malvae apterae are green, greyish green, pinkish red or yellowish (see first three pictures below). The terminal process of antennal segment VI is 4.8-5.8 times the length of its base. The longest hair on antennal segment III is 0.7-1.0 times the diameter of that segment and the apterae have 1-24 secondary rhinaria on that segment. The fused apical rostral segments are 1.1-1.4 times the length of the second hind tarsal segment. The femora and siphunculi are pale. Their siphunculi have no polygonal reticulation, are cylindrical on the distal half and are 1.8-2.2 times the pale caudal length. The body length is 1.5-3.2 mm.

The alate Acyrthosiphon malvae (shown giving birth in second picture below) has antennae longer than the body with 12-31 secondary rhinaria on antennal segment III. The abdomen is usually unsclerotized but may have small spinal and intersegmental pleural sclerites. The siphunculi and cauda are more slender than in the apterae.

The clarified slide mounts below are of adult viviparous female Acyrthosiphon malvae : wingless, and winged.

Micrographs of clarified mounts by permission of Roger Blackman, copyright AWP all rights reserved.

Acyrthosiphon malvae is found on many plants, but particularly herbaceous Rosaceae. There are many subspecies, mostly with specific host-plant associations.

  1. Acyrthosiphon malvae sensu stricto (first two pictures above) are pale green or red aphids on many Geraniaceae and Malvaceae worldwide, as well as plants in other families.
  2. Acyrthosiphon malvae subspecies agrimoniae (third and fourth images above) is yellowish green and found in flowerheads or on undersides of leaves of Agrimonia species (agrimony) in Europe and western Asia.
  3. Acyrthosiphon malvae subspecies poterii is bright salmon pink, yellowish or green and found on Poterium sanguisorba (= Sanguisorba minor) (salad burnet), and is only known from England.
  4. Acyrthosiphon malvae subspecies potha Börner is pale yellowish or greyish green and associated with Alchemilla species (lady's mantle) throughout Europe.
  5. Acyrthosiphon malvae subspecies rogersii (Theobald) is green or yellow-green, often shiny, and may form large colonies on young leaves of Fragaria (strawberry) in north and west Europe (Blackman & Eastop 2006).

The geranium aphid does not host alternate, all subspecies spend their entire life cycles on their respective host plants. In temperate climates overwintering is in the egg stage, but in warmer climates parthenogenetic reproduction continues all year. Including all the subspecies the distribution of Acythosiphon malvae is almost worldwide.

 

Biology & Ecology

Tambs-Lyche (1975) studied the dynamics of aphid populations on alpine tundra dry and wet meadow sites. The dominant species was Acyrthosiphon malvae subspecies potha living on Alchemilla alpina in the dry meadow and possibly on Potentilla crantzii in the wet meadow. Braschler et al. (2003) looked at the population dynamics of aphids in experimentally fragmented grasslands in the Jura mountains in Switzerland. Acyrthosiphon malvae was one of the commonest species and was more abundant in fragmented grassland than in control plots.

The geranium aphid is fairly common in southern England on both wild and cultivated cranesbills (Geranium species) and on cultivated geraniums (Pelargonium species). Those below were on Geranium himalayense being grown as a garden flower.

 

A small colony was also found on cut-leaved cranesbill (Geranium dissectum) (see below).

 

We have found large colonies of the green form of Acyrthosiphon malvae on the common dovesfoot cranesbill (Geranium molle) shown below.

 

The red forms of Acyrthosiphon malvae are less common - these were found on the popular garden flower Geranium 'Rozanne'.

Acyrthosiphon malvae is found as different host-specific subspecies on a variety of plant species including agrimony, a flowering plant in the Rosaceae.

We have found both the yellow and green forms of Acyrthosiphon malvae agrimoniae (see below) on common agrimony in southern England.

The geranium aphid also infests other ornamentals, such as Cineraria, but is rarely an important pest. Starý & Carver (1979) reported a new species of parasitoid from Acyrthosiphon malvae living on geranium (Pelargonium) in Australia.

 

Other aphids on same host:

Alford (2012) notes that Acyrthosiphon malvae is often found in company with other species, such as Neomyzus circumflexus.

  • Acyrthosiphon malvae has been recorded on 26 Geranium species.

    Blackman & Eastop list 23 species of aphid as feeding on Geranium species worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 14 as occurring in Britain: (Show British list).

  • Acyrthosiphon malvae has been recorded on 9 Pelargonium species.

    Blackman & Eastop list 11 species of aphid as feeding on 'geraniums' (Pelargonium species) 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).

  • Acyrthosiphon malvae has been recorded on 4 Malva species: musk mallow (Malva moschata), dwarf mallow (Malva neglecta), common mallow (Malva sylvestris) and garden tree-mallow (Malva thuringiaca).

    Blackman & Eastop list 20 species of aphid as feeding on mallows (Malva species) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 17 as occurring in Britain (Show British list).

    Acknowledgements

    Our particular thanks to Roger Blackman for images of his clarified slide mounts.

    We especially thank Plumpton College for their kind assistance, and permission to sample. Also Evelyne Turpeau for correcting our identification of an aphid that we previously had on this page. We had wrongly identified an alate Macrosiphum euphorbiae as Acyrthosiphon malvae.

    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

    References

    • Alford, D.V. et al. (2012). Pests of ornamental trees, shrubs and flowers. 2nd Edn. Manson Publishing.

    • Braschler, B. et al. (2003). Experimental small-scale grassland fragmentation alters aphid population dynamics. Oikos 100, 581-591. Full text

    • Starý, P. & Carver, M. (1979). Two new species of Aphidius Nees (Hymenoptera: Ichneumonoidea: Aphidiidae) from Australia. Journal of the Australian Entomological Society 18, 337-341. Full text

    • Tambs-Lyche, H. (1975). Dynamics of Aphididae populations on Hardangervidda. pp 84- in Wielgolaski, F.E. (ed) Fennoscandia Tundra Ecosystems. Springer-Verlag Berlin, Heidleberg.