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Dysaphis radicola

Apple-dock aphid

Identification & Distribution  Biology & Ecology 

Identification & Distribution:

Apterae of Dysaphis radicola are greyish-brown to lead grey or greyish-green, and are slightly wax powdered (see first picture below for colony on dock). Spinal tubercles are present on the head and abdominal tergites 8, or 7 and 8. Dysaphis radicola siphunculi are 2.0-2.5 times longer than the cauda.

 

The longest hairs on the third abdominal tergite are shorter than the basal diameter of the third antennal segment.

 

The alate of Dysaphis radicola (see second picture above) always has marginal tubercles on abdominal tergite 7.

In most of Europe Dysaphis radicola host alternates from Malus (apple) to the roots of Rumex (dock). The small primary gall near the apex of the apple leaf produced by the fundatrix comprises a longitudinal fold near the mid-rib (transverse for related Dysaphis  species). Subsequent generations roll and redden the lateral margins of leaves of Malus (apple) in the same way as its close relatives. Alates produced in the second generation migrate to the roots of Rumex (dock).

This host alternating aspect of Dysaphis radicola biology is lost in British (and other) populations, and the aphids stay on dock all year. On dock the aphids feed at the base of the plant where they are attended by ants. The ants usually tent over the colony with soil particles. Dysaphis radicola occurs throughout Europe, in the Caucasus, in Japan and Australia and possibly the USA.

 

Biology & Ecology:

We have found Dysaphis radicola on its secondary host (Rumex) in several locations in southern Britain near the South Coast. Populations are revealed by the activities of ants which tent over the aphids living at the base of the stem with soil particles (see picture below).

Although most of the aphid population is usually below the soil surface, they may also spread to infest the undersides of the lowest leaves of the dock plant as shown in the picture below.

 

Dysaphis radicola is attended by ants on dock roots. All those we have found were attended by Lasius niger (see pictures below).

 

Despite its subterranean feeding site and the presence of ants, Dysaphis radicola has been found to be parasitized by Lysiphlebus fabarum in considerable numbers (Rakhshani et al., 2013 ).

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

  •  Rakhshani, E. (2013). Tritrophic associations and taxonomic notes on Lysiphlebus fabarum (Marshall) (Hymenoptera: Braconidae: Aphidiinae), a keystone aphid parasitoid in Iran. Arch. Biol. Sci., Belgrade, 65(2), 667-68. Full text