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Ground elder leaf-curl aphidOn this page: Identification & Distribution Biology & Ecology Other aphids on the same host
Identification & Distribution
Aphis podagrariae induces characteristic tightly bunched leaf-curls on its main host, ground elder (Aegopodium podagraria, see first picture below). Adult apterae of Aphis podagrariae are black or blackish-green sometimes with areas of reddish-brown suffusion (see pictures below), and are usually without wax. Their antennae are 6-segmented with a terminal process 2.1-2.6 times as long as the base of antennal segment VI. The apical rostral segment (RIV+V) is 1.13-1.31 times the length of the second hind tarsal tarsal segment (HTII) (cf. Aphis fabae sstr., which has RIV+V 0.88-1.06 times the length of HTII).
The degree of abdominal sclerotization is variable. Stroyan (1984) reported that it varied with the size of the aphid, with larger adults having a complete series of bands over the thorax and abdomen, and smaller ones having bands only on tergites VII & VIII, but most of the specimens we have found only have bands on VII & VIII regardless of size. There are usually no marginal tubercles on tergites II-IV (cf Aphis solanella, for which about 50% of individuals have one or more marginal tubercles on tergites II-IV). The length of the hairs on the tibiae and femora are up to about twice the least width of the tibiae. The siphunculi are 0.75-1.45 times as long as the cauda (cf. Aphis brohmeri, which has siphunculi 1.26-1.58 times the length of the cauda). The length of adult Aphis podagrariae apterae is 1.44-2.47 mm. Immatures, especially third and fourth instars, often have small pleural white wax spots (see first picture below), and younger instars may have a more general wax dusting.
Alatae (see second picture above) are greenish-brown or dirty green, with a series of narrow dorsal abdominal sclerotic bands. They have 12-18 secondary rhinaria on antennal segment III, 1-7 rhinaria on segment IV and 0-2 rhinaria on segment VI.
The main host of Aphis podagrariae is ground elder (Aegopodium podagraria), but it has also been recorded on moon carrot (Seseli libanotis) and on Seseli (Libanotis) condensata. On young plants the aphids live in tightly bunched leaf-curls where they are loosely attended by ants. Later in the year aphids may occur on all parts of the plant, although they are not found clustered on the flowers (cf. Aphis fabae, which feeds preferentially on the flowers). There is no host alternation, and sexuales with mainly alate males develop in autumn. The ground elder leaf-curl aphid is found throughout Europe (except Spain & Portugal) and east into Central Asia. In Britain it is probably quite widespread in southern England, but its distribution is poorly known.
Biology & Ecology
We have often come across empty leaf-curl pseudogalls, most likely caused by this aphid, but only came across 'occupied' galls for the first time in July 2020. They were in a shady corner in an East Sussex coastal village where there was a small area of ground elder young regrowth. We found them again three weeks later in a shady location in another East Sussex village.
When the plants are young, very few aphids can be seen outside the galls - they remain packed inside feeding from the leaf undersides.
As soon as the plants start to flower, some of the aphids change their feeding site spreading out on to the flower stems (see pictures below).
Aphids on the stems, especially the immatures (see picture below), seem to be rather more waxy than aphids living in the galls, possibly to enhance their defences against predators.
Alatae are produced both when the aphids are living in the galls and later when they spread to the stems. They are quite variable in colour ranging from brown (see top of page) to a rather dirty green (see picture below).
Little is known about the natural enemies of Aphis podagrariae. Petrović et al. (2019) reported both Alloxysta arcuata and Alloxysta brevis as hyperparasitoids of Binodoxys acelephae parasitizing an Aphis species (possibly Aphis podagrariae) on Aegopodium podagraria.
We have found one mummy of this species, but no parasitoid emerged.
As regards predators we have found cecidomyiid larvae predating Aphis podagrariae (see picture below).
This aphid was apparently giving birth when it was predated. Aphids are probably more vulnerable to predators and parasitoids when giving birth, an activity which inhibits their normal escape responses.
Other aphids on the same host
Aphis podagrariae occurs on 1 species of Aegopodium (Aegopodium podagraria), and 2 species of Seseli (Seseli libanotis, Seseli condensata).