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Aphis frangulae species group
Alder buckthorn - willowherb aphidOn this page: Identification & Distribution Subspecies Biology & Ecology: Life cycle Colour Ant attendance Other aphids on the same host Damage & Control
Identification & Distribution:
Aphis frangulae apterae are generally dark green or blue-green, sometimes mottled (see pictures of apterae on the primary and secondary hosts below). Their abdominal sclerotic pattern is variable - it is usually confined to abdominal tergites 6-8 in smaller apterae, but broken bands are present in larger adults. The siphunculi are dusky or dark and are 0.85-2.16 times the length of the pale or dusky cauda. The body length of Aphis frangulae apterae is 0.9-2.4 mm.
Aphis frangulae alatae have 3-16 secondary rhinaria on the third antennal segment, 0-8 on the fourth segment and 0-3 on the fifth. The images below show adult apterous Aphis frangulae, dorsally and ventrally, in alcohol.
Until recently Aphis frangulae / gossypii was regarded as a cryptic group with uncertain separation between Aphis frangulae and Aphis gossypii. The two taxa were usually differentiated on the basis of life cycle and host plant. The work of Cocuzza et al. (2009a,b) and Carletto et al. (2009) has clarified the genetic separation between the two species in Europe.
In Europe, several subspecies are recognised:
There are several other postulate species of the Aphis frangulae group living on Lamiaceae, namely Aphis lamiorum on Lamium species, Aphis stachydis on Stachys species, and Aphis symphyti on comfrey (Symphytum officinale). Cocuzza & Cavalieri (2014) have suggested that these should be synonomized with Aphis frangulae, although this may be premature given their different life cycles.
Outside Europe, and for some populations within Europe, populations can usually only be identified as "Aphis frangulae group". Sexual forms occur in autumn. The closely related Aphis gossypii (cotton or cucumber aphid) is a cosmopolitan polyphagous pest of warm climates, and is a greenhouse pest in cooler climates.
Biology & Ecology:
Aphis frangulae is fairly easy to find in spring on its primary host, alder buckthorn, when the overwintering eggs have hatched, and young shoots are often crumpled or distorted by the feeding aphids (see picture below).
It commonly feeds on young leaves alongside the main vein or on young shoots (see picture below).
In late spring, Aphis frangulae migrates to one of its many secondary hosts. We have not yet found Aphis frangulae frangulae on either potato or its main secondary host, rosebay willowherb, but we have found the other subspecies, Aphis frangulae beccabungae, on germander speedwell (Veronica chamaedrys) (see pictures below).
The oviparae are apterous, and have strongly swollen hind tibiae which bear numerous pseudosensoria (scent plaques).
Both images above copyright Ian Barton, all rights reserved.
The males of all subspecies are winged, and are usually yellow-brown with dark cross bands on the abdomen. After mating (see above), the oviparae deposit the overwintering eggs on the primary host.
Aphis frangulae colour varies greatly, it is mainly different shades of green, but also orange-brown and greenish-black. The oviparae (see above) especially vary considerably from pale yellowish brown to dark green.
Although there is little mention of it in the literature, we have usually found Aphis frangulae on the primary host to be ant attended. The picture below shows Aphis frangulae feeding on alder buckthorn attended by Lasius niger.
The picture below shows Aphis frangulae feeding on alder buckthorn attended by a Myrmica species.
Other aphids on same host:
Blackman & Eastop list at least 5 species of aphid as feeding on alder buckthorn (Rhamnus frangula) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 3 as occurring in Britain (Show British list).
Damage and control
Aphis frangulae beccabungae may cause feeding damage to potatoes, and is also an important potato virus vector, transmitting potato virus Y and potato virus M. Kostiw (2009) reports on the abundance and species composition of aphids on potatoes in Poland from 1970-2005. The number of alates trapped in yellow dishes over this period declined markedly in all sampling sites. The authors attributed this decline to a decrease in the land area cropped for potatoes which by 2005 was only one fifth of the area cropped in 1970.