These are usually blue-gray, sometimes buff or with buff markings, 5-15 mm long; elliptical on hosts with wide leaves but elongate with rounded ends on hosts with narrow leaves; usually flat, but sometimes with a swollen appearance. These galls are occasionally found also on the stem. In the galls I have examined, there was only 1 larva/gall.
...
[He lists the following host records for this species, verified by both host and insect identification, most of which are now in the genus Ericameria:
Chrysothamnus affinis [Ericameria parryi var. affinis], C. albidus [E. albida], C. nauseosus [E. nauseosa var. nauseosa], C. nauseosus var. graveolens [E. nauseosa var. graveolens], C. greenei, C. plattensis [E. nauseosa var. nauseosa], C. viscidiflorus, Haplopappus armerioides [Stenotus armerioides], H. bloomeri [E. bloomeri], H. linearifolius [E. linearifolia].]
...
[He lists the following additional host species as possible Asteromyia hosts based on observations of galls only (no insect material available). They are included on this page based solely on the hosts' current inclusion in either Chrysothamnus, Ericameria, or near Stenotus. These could alternatively represent multiple undescribed Asteromyia species or host-range extensions of known species:
Chrysothamnus depressus, C. paniculatus [E. paniculata], C. parryi [E. parryi], C. teretifolius [E. teretifolia], Haplopappus arborescens [E. arborescens], H. cooperi [E. cooperi], Chrysothamnus pulchellus [Lorandersonia pulchella] - near Stenotus (Nesom 2020)]

Asteromyia chrysothamni

Elongate-elliptical, discolored blister on leaf or stem
Galls are buff to blue-gray

Hosts: C. albidus, C. nauseosus, C. greenei, C. parryi, C. "plattensis", C. viscidiflorus, and Haplopappus spp.

Distr: widespread in western North America: Saskatchewan to Texas and west.