Biology, images, analysis, design...
|"It has long been an axiom of mine that the little things are infinitely the most important" |
Grenade aphid, Garlic mustard aphidOn 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
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.