Pemphigus populiramulorum

Mordwilkoja vagabunda

Pemphigus betae

Pemphigus populiglobuli

Pemphigus populicaulis

Pemphigus populitransversus

Pemphigus nortonii

Pemphigus populivenae

Thecabius populimonilis

Pemphigus populiramulorum Riley

Gall on Populus sargentii Dode on new growth of twig

Very few galls of P. populiramulorum were found in Alberta. This aphid was first reported in the area in 1954 and since then a few galls were found each year. The gall (Fig. 6) is formed not on the leaf but on the new growth of the twig; as the aphid feeds, the twig swells and encloses it. The gall is round and has a transverse or vertical slit similar to that in the gall of P. populitransversus but with protruding lips. It is greenish at first but turns brown as the season progresses. In fall it remains on the tree and thus may be easily seen during the winter or early spring. 

Records of the distribution of P. populiramulorum Riley in Alberta are as follows: 1954, Grantham, Populus sargentii; 1956, Taber, Coaldale, P. sargentii. 

Mordwilkoja vogabunda (Walsh)

Gall on Populus sargentii [deltoides] formed from terminal bud, convoluted, bladder-like

The largest and most unusual gall on poplar in southern Alberta is caused by M. vagabunda. The primary host in the area is Populus sargentii. 

The gall caused by this species is usually large and conspicuous. The feeding of the fundatrix on the terminal bud results in the formation of a bladder-like gall. Fig. 9 shows the early stage of one of these galls and Fig. 10 the fully developed, convoluted gall. In autumn the galls do not fall but turn woody and remain on the tree the following year. Distribution of M. vagabunda in Alberta is as follows: 1930, southern Alberta, Populus species (MacNay, C. G. (in litt.)); 1948, Rocky Mountain House (Strickland, 1953); 1955, Grantham, Populus sargentii; 1957, Turin. 

Pemphigus betae Doane

Gall beside mid-rib on leaf of P. balsamifera or P. angustifolia (or, rarely, P. trichocarpa) 

This species, which is a pest of beets, swiss chard, spinach, and lettuce, causes considerable damage each year to sugar beets in southern Alberta and in some areas of the United States. P. betae can spread curly top virus and virus yellows among sugar-beet plants (Bennett and Wallace, 1938; MacLean, 1953). 

The galls are always on the leaf blades, usually next to the mid-ribs; generally there is only one per'leaf. Thev have been found in Alberta on the narrow-leaved cottonwood, P. mgustifolici; the balsam poplar, P. balsamifera; and, rarely, the black cottonwood P. trichocarpa. The fundatrix, which hatches from the overwintered egg, feeds near the mid-vein on the upper surface of the emerging leaf, causing the formation of a longitudinal depression, which increases in size to about half an inch long and a quarter of an inch deep (Fig. 1). Galls are usuallv green but may have a reddish tinge. 

Records of the distribution of P. betae in Alberta are as follows (the year denotes the first record from the area): 1929, Picture Butte, beets, lamb'squarters, pigweed; 1934, Lethbridge( Hillspring, Barnwell, beets (MacNay, C. G. (in litt.) Entomology Division, Ottawa); 1950, Monarch, Coaldale, Magrath, Raymond, Beta wulgaris, Chenopodium album, poplars; 1954, Diamond City; 1956, Pincher Creek, Barons, Hays, Turin, Welling, Stirling, beets, lettuce, Populus balsamifera, P. angustifolia, P. trichocarpa; 1957, Lundbreck, Black Diamond, Coleman, poplars. 

Pemphigus populiglobuli Fitch

Gall formed by swelling and twisting of petiole and leaf blade of Populus angustifolia James or Populus balsamifera L. (or, rarely, Populus trichocarpa T. and G.) 

The primary hosts of P. populiglobuli in Alberta are P. angustifolia, P. balsamifera, and, rarely, P. trichocarpa. The gall is formed at the junction of the petiole and leaf blade and is produced by a swelling at the base of the blade and at the top of the petiole (Fig. 2). The exit slit is produced by a slight separation of the twisted parts of the petiole and blade. Usually the gall is green but it may have a reddish tinge. 

Records of the distribution of P. populiglobuli in Alberta are as follows: 1954, Lethbridge, Magrath, Cardston, Coaldale, Picture Butte, P. angustifolia, P. balsamifera; 1957, Pincher Creek, Black Diamond, Lundbreck, Coleman, Blairmore, Crowsnest, Cyprus Hills, Medicine Hat, Waterton, Monarch, Macleod, P. balsamifera, P. angustifolia, P. trichocarpa

Pemphigus populicaulis Fitch

Gall on Populus sargentii [deltoides] formed by swelling and twisting of petiole and leaf blade

P. populicaulis is more common in southern Alberta than any other gall-forming aphid on poplar. The galls are found on trees along river banks and in many of the shelter belts in the irrigated areas. The primary host of this species in Alberta is P. sargentii Dode. 

The gall caused by this aphid is also formed at the junction of the petiole and blade of the leaf and is produced by a swelling and twisting at the base of the blade and at the top of the petiole (Fig. 3). In this respect it is similar in formation to the gall caused by P populiglobuli but differs in that it has a small, round exit (Fig. 19) whereas the exit of the gall caused by P. populiglobuli is a long, narrow, angular slit. When two galls of P. populicaulis are found on a single leaf, their shapes vary slightly from those of single galls (Fig. 19). 

In 1924 Glendenning reported water parsley, Oenanthe sarmentosa Presl, as the secondary host of P populicaulis. Strickland ( 1953) recorded Pemphigus brevicornis Harr. from potatoes, beets, and celery in August and September. Hottes and Frison (1931) collected P. brevicornis on roots of an umbrella plant, Erigeron sp., and a goldenrod, Solidago sp., and stated that the specimens might be the sexuparae of P. populicaulis. Cutright (1925) considered P. brevicornis as a synonym of Pemphigus lactucae Fitch. Thus, if Hottes and Frison and Cutright are correct, the name P. populicaulis will be replaced by P. lactucae, which has priority. 

Records of the distribution of P. populicaulis in Alberta are as follows: 1950, Picture Butte, Lethbridge, Coaldale, Taber, Vauxhall, Grantham, Turin, Iron Springs, Monarch, Macleod, Barnwell, Welling, Populus sargentii; 1953, Medicine Hat; 1957, Nobleford, Populus sargentii.

Pemphigus populitransversus Riley 

Gall on petiole of Populus sargentii [deltoides] with transverse slit 

P. populitransversus occurs on Populus sargentii in some localities along river banks and in shelter belts in irrigated areas of southern Alberta. According to MacNay (in litt.), this species was reported occasionally on Populus deltoides, P. tremuloides, and P. angustifolia in Alberta from 1929 to 1957. Although Essig (1926, pp. 259-261) indicated that this species may live on sugar beets, dock, and lettuce, it has not been found on these hosts in Alberta. Wene and White (1953) stated that P. populitransversus is an important pest of cabbage in Texas. Altllough no secondary host has been found in Alberta, winged forms were taken in Iargc numbers from turnips and cabbage in plots at the Lethbridge laboratory in 1954. However, when these lots were harvested and the roots of the plants examined, no aphids were found.

Galls are caused by the feeding of this species on the petiole of the popIar leaf. As the aphid feeds, the petiole swells on each side of the point of feeding and a spherical, green gall with a transverse slit is produced (Fig. 4). The galls vary in size from one-quarter to three-quarters of an inch in diameter. Although the galls generally have transverse slits, some were found near Cranford, Alberta, with vertical, transverse, or anguIar slits (Figs. 11-13). 

Records of the distribution of P. populitransversus in Alberta are as follows: 1929, Lethhridge, Bow River, -Arrowwood, Orkney, Macleod, Populus deltoides, Populus angustifolia, Populus tremuloides (MacNay, C. G. (in litt.)); 19.50, Turin, Picture Butte, Iron Springs; 1953, Medicine Hat; 1957, Barnwell, Taber, Vauxhall, Populus sargentii. 

Pemphigus nortonii Maxson 

Gall on Populus sargentii [deltoides] at junction of petiole and leaf blade with angular slit formed by twisting and swelling of petiole

Although P. nortonii was first reported from southern Alberta only four years ago, now it can be readily found on P. sargentii in shelter belts and on trees along riverbanks. As yet no secondary host has been recorded for this species.

The gall is formed on the petiole or at the junction of the leaf blade and the petiole and is produced by a swelling and twisting of the petiole only (Fig. 5). Although the gall is somewhat similar to that caused by P. populicaulis, it is generally larger, often growing to three-quarters of an inch or more in diameter. The exit from the gall is a long, semispiral slit and not a small, round opening as with P. populicaulis. 

Records of the distribution of P. nortonii in Alberta are as follows: 1953, Grantham; 1957, Taber, Turin, Lethbridge, Coaldale, Populus sargentii. 

This aphid was originally reported by the author in The Canadian Insect Pest Review (MacNay, 1955) as Pemphigus junctisensoriatus Maxson. Since then Maxson has checked the material and identified the aphid as P. nortonii. 

Pemphigus populivenae Fitch

Galls beside mid-rib on upper side of leaf of P. balsamifera

P. populivenae occurs in Alberta in very small numbers. In every locality where it was found in Alberta it was associated with galls caused by P. betae or P. populiglobuli. This species feeds close to the mid-rib on the undersides of the leaves of P. angustifolia or P. balsamifera, causing a gall (Fig. 7) about one-quarter to one-half of an inch long and about a quarter of an inch deep on the upper side of the leaf. The gall is similar to that of P. betae but is on the opposite side of the leaf. 

Records of the distribution of P. populivenae in Alberta are as follows: 1953, Edmonton (Strickland, 1953), Monarch, P. angustifolia, P. balsamifera; 1957, Lundbreck, Coaldale, P. balsamifera. 

Thecabius populimonilis (Riley)

Row of galls on either side of mid-rib of P. angustifolia or P. balsamifera

T. populimonilis is found on small trees along river banks in southern Alberta. The hosts of this species are P. angustifolia and P. balsamifera. 

The galls of this species do not contain colonies but only a single fundatrix or fundatrigenia. The fundatrix causes the gall, in which the young are produced, but shortly after the young are born they leave the gall and start to feed on the same leaf or on another leaf, causing galls to be produced at the point of feeding, usually in a row on either side of the mid-rib. The galls are pale green but may have a reddish tinge (Fig. 8). 

Records of the distribution of T. populimonilis in Alberta are as follows: 1948, Elk Island Park (Strickland, 1953); 1951, Lethbridge, Populus angustifolia; 1956, Monarch, Picture Butte, P. angustifolia; 1957, Spirit River, P. balsamifera. 

Gall Aphids on Poplar in Alberta: I. Descriptions of Galls and Distributions of Aphids