Pemphigus bursarius (Linnaeus, 1758)

Stem mothers form flask-shaped galls on the leaf petiole or occasionally on young shoots (Harper 1966). As many as three or four galls may occur on one leaf, each producing up to 78 alatae (Alleyne and Morrison 1977). First instars of this species include a "soldier" caste distinguished by their aggressive behaviour in attacking natural enemies (Rhoden and Foster 2002). Soldier aphids attack using sustained thrusts of their stylets to pierce the predator's cuticle. Alternatively, soldier aphids may use their legs to squeeze predators to rupture the cuticle and damage internal organs (Rhoden and Foster 2002). Such attacks are costly to the aphids but can kill predaceous maggots (Diptera: Syrphidae) to protect other aphids remaining in the gall.

Populus nigra L. var. italica is the primary host (Harper 1959a; Alleyne and Morrison 1977). Secondary hosts include lettuce, on which P bursarius is considered to be an economically important pest in Europe and in the United States (refs. in Harper 1966; Alleyne and Morrison 1977). Other secondary hosts include carrot (Apiaceae: Daucus sp.), lamb's quarters, and nipplewort Lampsana communis L. and Sonchus spp. (Asteraceae) (Palmer 1952). The aphid apparently has wide distribution in Canada, being previously reported from Alberta, Ontario, and Quebec (Harper 1966).

Pemphigus bursarius (Linnaeus)

Hosts. As winter host in petiole galls on Populus sp.; as summer hosts on lambsquarters (Chenopodium sp.), carrot (Daucus sp.), lettuce (Lactuca sp.), Lampsana communis and Sonchus sp., on roots. (Not recorded from region.)

Pemphigus bursarius (Linnaeus) Poplar‑Lettuce Aphid, Lettuce Root Aphid

Galls on Populus spp. (most commonly P. nigra) are yellowish or reddish when mature, purse-shaped, always formed on leaf petioles (fig. 131L, and see influentialpoints.com/Gallery). The fundatrix is greyish green, slightly wax-dusted. Alatae (BL 1.6-2.5 mm) leave the gall through a lateral opening over an extended period from late May to September, with peak emergence in late June-July (northern hemisphere). They found colonies mainly on roots of Compositae/Asteraceae (e.g. Cichorium, Lactuca, Lampsana, Sonchus, Taraxacum, Tussilago). Many of the records of P. bursarius from roots of plants in other families may be referable to other Pemphigus spp. Return migration of sexuparae to poplar is in October-September, but anholocyclic overwintering on roots of secondary hosts is common. P. bursarius occurs in Europe, across Asia to eastern Siberia (Babichev & Kirichenko 2020), northern and southern Africa, North and South America, and (perhaps) Australia and New Zealand. There is some uncertainty about its occurrence in Australia and New Zealand because, although bursarius-like aphids occur in bursarius-type galls on Populus and are also recorded from Sonchus roots, the secondary host populations are mainly recorded from Amaranthaceae and Polygonaceae. Miller et al.. (2005) found genetically distinct populations on different secondary host plants, indicating a complex of races and/or subspecies. Dunn (1960a) studied gall formation and (1960b) reviewed natural enemies. Alleyne & Morrison (1978a, b) gave accounts of its biology and natural enemies in Quebec. See also Blackman & Eastop (2000). 2n=20.

Pemphigus bursarius
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Hosts: Populus nigra var italica

This aphid induces tubular, flask-shaped, mid-petiole galls on Lombardy poplar.

Range: Europe, widespread across North America

Pemphigus bursarius

Galls on Lombardy poplar (Populus nigra L. var. italica Muenchhausen) formed by petiole swelling only, no twisting

This aphid is regarded as a major pest of lettuce in Europe (Dunn 1959; Judge 1967; Stroyan 1964) and in the United States (Lange et al. 1957; MacDaniel 1958). Little is known concerning this species in Canada although Harper (1966) found them on Lombardy poplar in Alberta and indicated that it has the potential of becoming a rather important lettuce pest in North America. Reports of attacks by this aphid on lettuce in Nova Scotia (Creelman 1969) and in Quebec (Lange and Cartier, pers. comm.) are further indicators. The primary author is currently engaged in a study of this species.

The galls of P. bursarius are flask-shaped (Fig. 4) and are formed on the petioles of leaves of Lombardy poplars. Quite often as many as three or four galls may be present on a single leaf petiole. In such instances the shape of the gall is modified depending on the degree of overlap (Fig. 5). Surveys of poplars conducted during 1972 and 1973 in regions on the west end of Montreal Island and in Pincourt, Ile Perrot, Que., indicate that each gall is the product of a single stem mother or fundatrix hatched in early spring from an overwintering egg. An average of 78 alates per gall were produced by 20 galls examined, and these alates escape from the gall cavity during mid-June and mid-July (by means of tiny pores on the lip). Present studies indicate that this aphid colonizes many alternate hosts, but lettuce is the only one of economic importance.

Pemphigus bursarius L.

[A photo of this gall appears on page 2 of the pdf]

This species, commonly known as the lettuce root aphid, has been found in the United States (Palmer 1952), Europe (Stroyan 1964), New Zealand (Cottier 1953). North Africa, and the Middle East (Bodenheimer and Swirski 1957). In Canada it has been found on Lombardy poplars in Ontario and Quebec. P. bursarius has also been reported as an important pest of lettuce in England and the United States (Dunn 1959; Lange et al. 1957).

In Alberta P. bursarius was first found in 1963 on a few specimens of Populus nigra L. var. italica Muenchhausen in a garden at Lethbridge, and could become a pest of lettuce in southern Alberta. The galls, which are generally on the petiole but are occasionally found on young shoots, vary in size and shape but are purseor flask-shaped (Fig. 2). In the gall are the fundatrix and her offspring.

Dunn (1959) considered that synonyms of P. bursarius are Aphis bursarius L., Pemphigus glandifomis Rudow, P. lactucarius Passerini, and Eriosoma populi Mosley.