A Leaves 1- or 3-foliate, flowers in leafy racemes => Subgenus Sarothamnus

B Leaves 3-foliate; flowers in leafless racemes => Subgenus Cytisus

1a On parts above ground => 2

1b Roots with rotund, cylindrical, also hand-shaped or coralloid branched, usually laterally inserted nodules. Cytisus spp.: Rhizobium leguminosarum

2a On shoot axis or leaves => 4

2b On shoot tips or lateral buds => 3

3a Lateral buds developed into compact, ± half globular tufts of leaves; leaves stunted, rolled upwards, strongly pubescent. C. aetnensis, albus: Aceria genistae

3b Axillary bud transformed into an acuminate, densely pubescent egg-shaped gall (8 x 4 mm long) with large larval chamber. C. tridentatus: Asphondylia pterosparti

3c Rotund or egg-shaped, bud-like closed, greenish, abnormally pubescent galls on shoot tip or in leaf axils. Inner wall covered with fungus. Containing a single larva. Cytisus spp.: Asphondylia cytisi

4a Slightly bulging swellings on stems and leaves, soon covered with sori => 7

4b Malformations caused by animals => 5

5a Galls on shoot axis => 6

5b Leaflets rolled or folded upwards, pod-shaped. Larvae orange-red. C. supinus; Lembotropis nigricans: Wachtliella niebleri

5c Leaves and usually shoot tip disfigured. Leaf margin rolled upwards. Cytisophyllum sessilifolius; Lembotropis nigricans: Aceria cytisi and/or Aceria grandipennis

6a Bulges on young axial parts, bearing aecia. Only hypophyllous telia. Telia, light brown, 1 mm, in circles on yellowish swollen leaf spots. Teliospores smooth, apically thickened; pedicel hyaline, persistent. Cytisus spp.; Lembotropis nigricans: Uromyces pallidus

6b Malformations similar but aecia rare. Spermogonia and aecia hypophyllous, also on the stems. Telia dark brown; spores coarsely verrucose; top with a low hyaline papilla; pedicel hyaline, deciduous, short. Cytisus spp.; Lembotropis nigricans: Uromyces fulgens

1a On parts above ground => 2

1b Root with many, laterally inserted globular, cylindrical or terminally hand-shaped to coralloid partitioned nodules. Sarothamnus spp.: Rhizobium leguminosarum

2a Galls on flowers and fruits => 15

2b Malformations on vegetative organs => 3

3a On buds, shoot tips or leaves => 9

3b On shoot axis => 4

4a Swellings longer than 5 mm => 7

4b Swellings smaller, sometimes ± coalescing => 5

5a Inducers inside galls => 6

5b Young stems often with many, rotund-oval, rimmed depressions containing the inducer. Sometimes coalescing and distorting the axis. Sarothamnus spp.: Chionaspis salicis

5c Sporadically has been observed: Viscum album

6a Up to 2 mm long, one-sided, often many swellings close to shoot tip, often situated below a bud and associated with a shortening of the axis. Containing a single orange-red larva. C. scoparius, striatus: Janetiella tuberculi

6b Galls 2–3 mm long, oval to spindle-shaped; terminally on main- and side shoots. Larvae sometimes occurring simultaneously in inconspicuous swellings on petioles and leaf veins. Containing orange-yellow larvae. C. grandiflorus, scoparius, striatus: Contarinia scoparii

6c Terminal swelling of twigs, usually one-sided, one-chambered with fleshy walls, 3.5 x 3.0 mm long. Containing a single red larva. C. patens, scoparius, striatus: Dasineura trotteri

7a Gall contains a larva with head capsule => 8

7b Larva lacking head capsule; at first whitish, later on greenish; solitary in one-sided, spindle-shaped swelling, 10–25 mm long and about 4 mm high, at first pale green, later on yellow-grey with exit hole provided swelling on thinner twigs. C. scoparius: Hexomyza sarothamni

7c One-sided stem gall, subcylindrical, up to 15 x 4 mm long, larval chamber oblong provided with exit hole. C. patens: Agromyza kiefferi

8a Root parts close to surface, also lower twigs up to about 25 cm above surface with rotund-oval swelling. The older larva bores a screw-like tunnel above the gall between bark and wood. Containing a single larva. C. scoparius: Agrilus cinctus

8b Expanded, 40–80 mm long, up to 5 mm high, multi-chambered swelling on 2- to 3-years old twigs. Containing many larvae. C. scoparius: Pirapion immune

8c Twig galls, sometimes very slight swelling. C. scoparius: Protopirapion atratulum

8d Twig galls. Minor rotund or spindle-shaped swelling, usually crazed on one side with central larval chamber. C. grandiflorus: Protopirapion kraatzii

9a Galls restricted to a malformation of the unopened axillary buds, or develop as localised swelling of petioles and veins => 12

9b More expanded, strongly pubescent malformations on ± unfolding lateral buds or curling of many leaves on shoot tips => 10

10a Malformations strongly pubescent => 11

10b Several leaves at the tip of young shoots rolled downwards. C. scoparius: Acyrthosiphon pisum subsp. spartii

10c Terminal bud. Gall egg-shaped (3–4 x 2.5–3 mm long), green, rather thick, fleshy wall made by the fused scales. In central larval chamber lives a single brick-red larva. C. patens: Janetiella maculata

11a Lateral buds ± swollen, with grey-felt-like pubescence, rotund, transformed into a cauliflower-like tuft, up to 15 mm long. Shoot axis succulent, thickened. Leaflets atrophied, abnormally pubescent, their margins bent upwards. Sarothamnus spp.: Aceria genistae

11b Side shoots swollen, clustered, tuft-like, shortened and lanky; ± discoloured and abnormally white pubescent. Leaves stunted, glabrous. C. scoparius:
Unidentified gall mite

11c Terminal internodes shortened and leaves inserted in tuft-like clusters. C. scoparius: Unidentified gall midge

12a Malformations of lateral buds => 13

12b Stalks of leaves or leaflets, and leaf veins often with inconspicuous, oblong-oval or spindle-shaped swellings, up to 2 mm long, one-chambered, yellowish. Containing a single orange-coloured larva. C. grandiflorus, scoparius, striatus: Contarinia scoparii

12c Leaflet folded upwards, transformed into a fleshy inflated pod, hooked behind, red-tinged. Containing several red larvae. C. scoparius: Dasineura vallisumbrosae

13a Galls glabrous => 14

13b Galls ± distinctly white pubescent; about 8–12 mm long; ± egg-shaped, with ± long acuminate distal extension. Inner wall with mycelium. Containing a single larva. C. scoparius: Asphondylia pilosa

14a Galls acuminate egg-shaped, ± short stalked, succulent, 7–10 (12) mm long, one-chambered; tip often oblique. Inner wall with mycelium. Contains a yolk-yellow larva. C. grandiflorus, scoparius: Asphondylia sarothamni

14b Galls ± tube-shaped, up to 10 mm long and 2–3 mm broad, one-chambered; tip opening, enveloped by 3–6, slightly diverging slender lobes, above the larva; inside with long, white, ± rigidly upwardly directed hairs. Containing a single orange-yellow or -reddish larva. C. eriocarpus, grandifloras, patens, scoparius, striatus welwitschi: Dasineura tubicoloides

15a Fruit galls => 19

15b Flowers ± swollen and unopened => 16

16a The gall inducing larvae occur in the cavity within the flower parts; head capsule absent; midge galls => 17

16b Flower ± pouch-like, swollen, unopened, soon drying. In the weakly or almost globularly swollen, stunted ovary a beetle larva develops. C. scoparius: Tychius parallelus

17a nner gall wall without mycelium => 18

17b Swollen bud remains unopened but sometimes displaying the yellowish-orange corolla parts. Inner wall of gall with dense, white-grey mycelium. Containing a yolk-yellow larva. C. scoparius: Asphondylia sarothamni

18a Flower buds swollen, often allowing the upwardly curved styles to protrude. Containing a pale red larva. C. scoparius: Jaapiella sarothamni

18b Flower bud weakly swollen, unopened or half opened. Later on blackening and drying. Larva white to yellowish, jumping. C. scoparius: Contarinia anthonoma

19a Malformations caused by gall midge larvae => 20

19b Pod ± stunted; with rotund-oval swelling, almost lenticular; sometimes laterally bent. Containing a single larva. C. scoparius: Tychius parallelus

20a Pod ± stunted; with rotund- to oblong oval swelling, 10–12 x 3–5 mm long, ± yellowish, usually situated in proximal part. Inner wall with grey-white mycelium. Containing a single yolk-yellow larva. C. scoparius: Asphondylia sarothamni

20b Pod developing almost normally; with several weak, yellowish tubercles, about 2 mm long. Contains several ivory-white, jumping larvae. C. scoparius: Contarinia pulchripes