Diplolepis rosaefolii (Cockerell, 1889)

Nomenclature: Rhodites rosaefolii Cockerell, 1889 | Rhodites lenticularis Bassett,

Feeds on: Induces galls on Rosa acicularis Lindl., R. woodsii Lindl., and R. arkansana Porter

Distribution: United States: California, Colorado, Illinois, Pennsylvania; Canada:British Columbia, Manitoba, Newfoundland and Labrador, Nova Scotia, Saskatchewan,Yukon

Diplolepis rosaefolii

Leaf galls
Rose Lentil Gall. Lentil-shaped thickenings of parenchyma, more conspicuous on under side, single or in small group, 3 mm in dia, dropping with the leaf.

[Photo caption]

342. On a wild rose. Adults emerged May 11-June 14 (Chi). Brodie reared adults from galls on Rosa blanda in June.

Diplolepis rosaefolii

Mature galls are lenticular (Fig. 5), 2.0-2.5 mm thick and 3.0-5.5 mm in diameter, appearing as circular swellings protruding from both the adaxial and abaxial surface of leaflets. Galls are single chambered and occur either scattered over the surface of leaflets, or are so densely packed and coalesced that entire leaves are obscured.

Diplolepis rosaefolii (Cockerell)

Diplolepis rosaefolii was first described from galls collected in Colorado (Cockerell 1889). It has the widest distribution of all Nearctic Diplolepis, being found from British Columbia to Newfoundland and from the Yukon and Alaska to Colorado. It is a common species on the prairies and in southern British Columbia.

Diplolepis rosaefolii is one of the smallest adults in the genus, along with D. fusiformans, averaging about 2 mm in length. Galls are lentil-shaped (Fig. 20), 2.0–2.5 mm thick, and 3.0–5.5 mm in diameter and protrude from both the adaxial and abaxial surface of leaflets. Galls usually occur scattered over the leaf, although sometimes they are densely packed and coalesced. They are usually the same colour as the host leaflet when immature but turn either pale yellow or bright red when mature. They are single-chambered with the larva lying parallel to the leaflet surface (Fig. 21). Immature galls appear from late spring to late summer, indicating the adults have a lengthy activity period.

This species appears to be the least host specific of all Diplolepis in Canada, being found on the three prairie species of Rosa. Galls are most common on short, bushy R. woodsii growing in dry sites in the Mixed Grassland Ecoregion. Most galled leaves abscise in mid-fall, but heavily galled leaves sometimes remain on the plants over the winter.

Galls of D. rosaefolii from coulees of the South Saskatchewan River near Langham, Saskatchewan (west of Saskatoon), illustrate the community typical for this species (Fig. 44C). Commonly, 50–75% of all inhabitants are inducers throughout the range of this species. Periclistus are also common, frequently accounting for 12–25% of all inhabitants. Eurytoma, Pteromalus, and Glyphomerus stigma are the most common parasitoids (Fig. 44C). The percentage of galls inhabited by Periclistus is high in mid-season but drops to less than 15% by the end of the season (Table 5). Fewer Periclistus larvae occur per gall than in the galls of other species (Table 4). About one-third of the Eurytoma exit galls in the year of induction, as do over half of the Pteromalus (Table 3).

Rhodites lenticularis n.sp.

'Lentile-shaped galls in parenchyma of the leaves of Rosa lucida, showing on both the upper and underside and from 0.10 to 0.15 of an inch in horizontal, and 0.08 inch in vertical diameter. Comparatively few of the galls are single. Most are confluent and of irregular outline, and in some instances the entire leaf is covered, while in others the right or left lobe is thus covered. These galls resemble the European species R. spinosissimae, but the latter are more nearly globular and their vertical diameter is one-half more, while the horizontal is considerably less. The larval cell is much larger and the walls much thinner than in R. lenticularis...'