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Identification & Distribution:

In springtime Pachypappa tremulae fundatrices (not shown here) may be found on the twigs of aspen (Populus tremula. They are unusually large (body length 5.0-6.6 mm) and are almost globular. They are a dirty reddish or yellowish brown colour, but appear silvery as they are covered with long fine hairs. They have no siphuncular pores and do not secrete any wax. The offspring of the fundatrix move on to the new shoots and form a rosette like leaf nest (see first picture below) formed by bending of the leaf petioles and stunting of growth of the shoot.

 

Guest images copyright Volker Fäßler,  all rights reserved

These offspring all develop to winged individuals (see second picture above) which are orange or reddish brown, covered in wax and with very small siphuncular pores. They migrate in June to form colonies on the roots of spruce (Picea abies). Pachypappa tremulae apterae on spruce are pale yellowish white with tufts of wax posteriorly. Sexual forms then return to aspen in autumn. Pachypappa tremulae is widely distributed in the northern palaearctic, east to China and Japan.

 

Biology & Ecology:

Baker (2012)  found leaf-nests containing Pachypappa tremulae on most aspen trees in June 2012 at Dundreggan in Scotland. However, none was found on the same site in July 2013, probably because the unusually hot weather that year had already prompted a move to spruce roots, the summer host (Dransfield & Brightwell, 2013 ).

Guest image copyright Volker Fäßler,  all rights reserved

Allan Watson Featherstone (2012)  describes the leaf nest of Pachypappa tremulae at Dundreggan together with some excellent photos. The aphids suck the sap from one side of the leaf petiole. This causes each infested leaf to droop downwards, so forming a tent-like structure known as a leaf nest. He points out that the wax coating these aphids has a defensive purpose against potential predators.

Guest image copyright Volker Fäßler,  all rights reserved

 

Damage and control

Shrimpton (1985)  reported the presences of Pachypappa tremulae as a conifer pest in several nurseries in British Columbia and Alberta. The aphid was usually found on container spruce and spruce potted for grafting with few records from bare root. The white waxy infestations were on the surface of the plug between the roots and the container wall, closer to the top of the plug than the bottom. However, most nurseries with infestations of this root aphid did not report any chlorotic or undersized individuals, and it was anticipated that damage would be minimal if nutrients and moisture were adequate.

Acknowledgements

Our especial thanks to Volker Fäßler  for several images above.

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

  •  Baker, E. (2012). Aphids and their parasitoids at the Dundreggan estate. Report.

  •  Dransfield, R.D. & Brightwell, R. (2013). Aphids and their natural enemies and mutualists at Dundreggan, Scotland. Report, InfluentialPoints.com. Full text 

  •  Shrimpton, G. (1985). Four insect pests of conifer nurseries in British Columbia. USDA For. Serv. Gen. Tech. Rep. INT-185 Full text