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Lipaphis alliariae

Grenade aphid, Garlic mustard aphid

On this page: Identification & Distribution  Other aphids on the same host  Damage & Control 

Identification & Distribution

Adult apterae of Lipaphis alliariae have a blue-green dorsum largely covered by four longitudinal series of dark sclerites (see pictures below). The antennal terminal process is 1.2-1.35 times the length of the siphunculi (cf. Lipaphis erysimi  which has the antennal terminal process is 0.8-1.15 times the length of the siphunculi). The third antennal segment is 1.0-1.8 times the length of the siphunculi (c.f. Brevicoryne brassicae  which has the third antennal segment 2.5-3.7 times the length of the siphunculi). Abdominal tergites 1 and 7 are without marginal tubercles. The siphunculi are slightly swollen and are 1.1-1.6 times the length of the cauda (cf. Brevicoryne brassicae which has siphunculi 0.8-1.0 times as long as the cauda). The body length of adult apterae is 1.6-2.1 mm.

Both images copyright Stéphane Claerebout, all rights reserved, with thanks to Willem Ellis of Plant Parasites of Europe 

Lipaphis alliariae feeds on the stems and seed pods of garlic mustard (Alliaria petiolata), it does not host alternate. Sexual forms, wingless males and oviparae, occur in October.

The grenade aphid (so called presumably because of the resemblance of the aphid in dorsal view to a hand grenade) has a rather patchy distribution in Europe occurring in France, Sweden, Finland, Poland and Germany, but not in Spain, Italy, Britain or Norway. It has been seen both as a minor pest and as a potential biological control agent depending on how its host plant is viewed.

 

Other aphids on the same host

Blackman & Eastop list 9 species of aphid  as feeding on garlic mustard, hedge garlic, Jack-by-the-hedge (Alliaria petiolata) worldwide, and provide formal identification keys.

Of those aphid species, Baker (2015)  lists 8 as occurring in Britain: Aphis gossypii,  Brevicoryne brassicae,  Lipaphis erysimi,  Myzus ascalonicus,  Myzus ornatus,  Myzus persicae,  Nasonovia ribisnigri,  and Rhopalosiphoninus latysiphon.

 

Damage and control

In Europe garlic mustard (see picture below of flowers and developing seed pods) is grown on a small scale in herb gardens since it can be used as an alternative to garlic.

The grenade aphid Lipaphis alliariae causes damage to garlic mustard by severely distorting the seed pods (see picture below). The normal, slightly-curved, long pods on the left of this seed head were largely unaffected.

Image copyright Stéphane Claerebout, all rights reserved, with thanks to Willem Ellis of Plant Parasites of Europe 

Lipaphis alliariae is therefore considered a (minor) pest in Europe.

The situation is rather different in America where garlic mustard is a serious invasive pest especially in forests (Rodgers et al., 2009 ), and efforts are being made to find a suitable biological control agent (Blossey et al., 2001 ). So far three European weevil species (Ceutorhynchus spp) seem to offer the best prospects, but a Lipaphis aphid has been noted in the field in America causing twisted distorted seedpods (Van Riper & Becker, 2014 ). The species was identified as Lipaphis brassicae (a non-existent species), but the author presumably meant Lipaphis pseudobrassicae, a serious polyphagous pest species in America. That species clearly cannot be used for biocontrol, but the monophagous (single-host) Lipaphis alliariae may indeed offer good control prospects.

Acknowledgements

We particularly thank Stéphane Claerebout, and Willem Ellis of Plant Parasites of Europe,  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

  • Blossey, B. et al. (2001). Developing biological control of Alliaria petiolata (M. Bieb) Cavara and Grande (garlic mustard). Natural Areas Journal 21, 357-367. Full text 

  • Rodgers, V. et al. (2009). Ready or not, garlic mustard is moving in: Alliaria petiolata as a member of Eastern North American forests. Bioscience 58, 357-367. Full text 

  • Van Riper, L.C. & Becker, R.L. (2014). Garlic Mustard (Alliaria petiolata) monitoring in Minnesota 2005-2013. Report to the Legislative-Citizen Commission on Minnesota Resources 58, 357-367. Full text