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"It has long been an axiom of mine that the little things are infinitely the most important" (Sherlock Holmes)

 

 

Identification & Distribution

Adult apterae of Impatientinum asiaticum have an extensive shiny black dorsal shield (see first picture below). The un-sclerotized lateral and ventral parts of the abdomen are green, pink or red. The fused apical segments of the rostrum (RIV+V) are 0.84-1.0 times the length of the of the second hind tarsal segment. The apices of the tibiae are dark or black, and the distal parts of the femora are black (cf. Impatientinum balsamines which has the apices of the tibiae pale, and the distal parts of the femora pale or dusky). The siphunculi are black and are 0.63-0.81 times the length of the third antennal segment (cf. Impatientinum balsamines which has the siphunculi 0.57-0.66 times longer than the length of the third antennal segment).

Both images above copyright Marco de Haas,  all rights reserved.

The alate Impatientinum asiaticum (see second picture above) is green or pink with a more fragmented dorsal shield than the aptera.

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

Impatientinum asiaticum is thought to have originated in central Asia. The north Indian subspecies host alternates from Smilax to Impatiens, but outside of Asia the species has lost its primary host. In Europe it lives all year round on the invasive Himalayan balsam (Impatiens glandulifera) and especially small balsam (Impatiens parviflora). It feeds on the undersides of leaves along the main veins, and on the flower stalks. It is not attended by ants, and produces sexual forms on the secondary host. Impatientinum asiaticum is found in south-east England, most of Europe and parts of Asia.

 

Biology & Ecology

The host plants of the Asian balsam aphid are Himalayan balsam (Impatiens glandulifera) and small balsam (Impatiens parviflora). We have often searched plants of Himalayan balsam (see first picture below) for this aphid in southeast England (mainly in East Sussex) but have yet to find it. As far as we know Impatientinum asiaticum has only so far been recorded in England from Middlesex and Surrey.

Second image above courtesy of Moelkuel, under the Creative Commons Attribution 3.0 Unported license. 

In Europe Impatientinum asiaticum is more widespread, and Marco de Haas found it commonly on small balsam (see second picture above) in the Netherlands. The pictures of the live aphid on this page come from Marco. The aphid has several colour forms and may be green, pink or red - the pictures below show fourth instar immature alates of the green and pink forms.

Image above copyright Marco de Haas,  all rights reserved.

Image above copyright Marco de Haas,  all rights reserved.

Despite having lost its primary host, the Asian balsam aphid has retained its sexual forms, and winged males and oviparae may be found in autumn on balsam in Europe.

 

Other aphids on same host:

Blackman & Eastop list 9 species of aphid  as feeding on Himalayan balsam (Impatiens glandulifera) worldwide, and provide formal identification keys.

Of those aphid species, Baker (2015)  lists 5 as occurring in Britain: Aphis fabae,  Aphis nasturtii,  Impatientinum asiaticum, Impatientinum balsamines, Myzus ornatus. 

Blackman & Eastop list 4 species of aphid  as feeding on small balsam (Impatiens parviflora) worldwide, and provide formal identification keys.

Of those aphid species, Baker (2015)  lists all 4 as occurring in Britain: Aphis fabae,  Aphis gossypii,  Aphis nasturtii,  Impatientinum asiaticum.

 

Beneficial effects

Himalayan balsam is a major invasive pest in many parts of the world including Europe and North America. It frequently out-competes local plants, especially on river banks. There it promotes river bank erosion due to the plants dying back over winter, leaving the bank unprotected from flooding (Greenwood et al., 2014 ). Various methods have been used to control Himalayan balsam including manual destruction of the plants and release of a rust fungus.

Small balsam is also considered a dangerous alien plant, especially in Slovakia where it is invading forest stands. Eliasova (2011)  evaluated the aphid Impatientinum asiaticum as a potential biocontrol agent of small balsam. It was concluded that, in certain circumstances, the aphid could play a role in suppressing Impatiens parviflora populations alongside other agents such as rust fungus.

Acknowledgements

We are very grateful toMarco de Haas  for his images of Impatientinum asiaticum, especially so since he obtained some of them (those of the adult aptera) at our request.

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

  • Eliasova (2011). The phenological synchrony between alien aphid Impatientinum asiaticum Nevsky and its host - alien plant Impatiens parviflora Dc. In: Siska, B. et al. (eds) Bioclimate: Source and Limit of Social Development. International Scientific Conference, 6-9 September 2011, Topolcianky, Slovakia. Full text 

  • Greenwood, P. et al. (2014). The potential influence of the invasive plant, Impatiens glandulifera (Himalayan Balsam) on the ecohydromorphic functioning of inland river systems. Geophysical Research Abstracts. EP31C-3570. Abstract