Plant Parasites of Europe

leafminers, galls and fungi

gallers on Genista

Dichotomous table for gallers on Genista

(incl. Chamaespartium, Cytisanthus, Echinospartium)

by Hans Roskam

1a On parts above ground => 2

1b Rotund-oval to cylindrical, about 8 (10) mm long, apically ± forked or fan-shaped broadened, laterally attached nodules on main- and adventitious roots. Genista spp.: Rhizobium leguminosarum

2a On inflorescences, flowers or fruits => 15

2b On vegetative parts => 3

3a On shoot tip or -axis => 9

3b On lateral buds or leaves => 4

4a On buds => 7

4b On leaf blades => 5

5a Wart- or pustule-shaped galls on leaf blade => 6

5b Leaflet rolled over its length, slightly thickened and enlarged, ± yellowish or reddish, strongly pubescent. Galls usually with several terminally on non-flowering shoots. Containing a single white larva. G. pilosa: Dasineura genistarum

6a Compact, ± yellowish translucent warts on basal leaves; infestation encroaching onto young axial parts. G. tinctoria: Synchytrium aureum

6b Soft egg-shaped pustules, up to 2 mm long, ± yellowish-green. The emerged larva leaves the ‘procecidium’ (oviposition scar, not a true gall, which collapses soon afterwards) and feeds freely on the leaf blade. G. pilosa, tinctoria, etc.: Unidentified sawfly

7a Relatively small midge galls, up to 7 mm long, rather constant in shape, glabrous or sometimes in young stage ± strongly white pubescent => 8

7b The buds develop into small, ± witches’ broom-like structures bearing clustered, almost scale-shaped, strongly pubescent leaves. Genista spp.: Aceria genistae

8a Axillary leaf bud transformed into a glabrous gall, about 7 mm long, 4 mm thick, with large central chamber. Inner wall covered with mycelium. Containing a single larva. Genista spp.: Asphondylia genistae

8b Buds enlarged, transformed into an egg-shaped to oblong-oval tuft; with external white pubescence, at first bud-like, then apically spreading; containing one to several, at first white, later on pale pink-coloured larvae. Genista spp.: Jaapiella genisticola

8c Globular galls covered with long snow-white hairs at shoot tip or in leaf axil. G. scorpius: Dasineura scorpii

9a Galls exclusively or mainly on the buds or leaves of apical shoots => 10

9b The terminal axial parts are transformed over several, ± strongly shortened internodes into a broad, long-, rarely rotund-oval, irregular bulging, spongy, sparsely haired swelling; usually multiple-, rarely single-chambered. Tips of terminal and, if present, lateral shoots often with tuft-like clustered, ± reduced, basally thickened leaves. Larvae flesh-coloured, jumping. G. corsica, depressa, germanica, tinctoria: Contarinia melanocera

9c Terminal internodes shortened, excessively branched, bearing clustered tufts of small leaves, up to 3 mm long, underside pubescent, leaf blade wrinkled at top or curved, spoon-like. Malformation up to 20 mm across. Genista spp.: Aceria genistae

9d One-sided swelling of twig (10 x 3 mm), crazed at surface, with oblong larval chamber inside. G. aetnensis, tinctoria: Hexomyza cf. sarothamni

9e Internodes shortened, bearing enlarged, densely white pubescent leaves which are clustered in a rosette. G. scorpius: Dasineura scorpii

9f Subterranean part of stem with one-sided, discoloured malformations of variable length and shape, single or clustered in irregular complexes due to expansion of parenchyma; compact. Caused by large numbers of black aphids. Genista spp.: Aphis cytisorum

10a Tufts of leaves on G. sagittalis => 14

10b Tufts of leaves on other Genista species => 11

11a Tufts abnormally haired => 12

11b Leaves of tufts glabrous, basally thickened and broadened. Many larvae. G. germanica, tinctoria: Dasineura sp.

12a Malformations caused by gall midges => 13

12b Axis of shoot tip distinctly shortened. Apical- and usually some lateral buds developing into stub-shaped, partially branched shoots bearing markedly reduced, almost scale-shaped and densely haired clustered leaves. Genista spp.: Aceria genistae

13a Oblong, abnormally haired tuft of leaves on G. januensis, pilosa, tintoria. Leaves ± keel-shaped rolled inwards. Containing orange-coloured larvae: Jaapiella genistamtorquens

13b Acuminate rotund to oblong-oval, about 10 (15) mm long tufts of leaves with ± thickened, partially almost mussel-like broadened leaves and sometimes densely, short, white pubescent. Larvae at first white, then pale pink. Genista spp.: Jaapiella genisticola

14a Dense white or grey pubescent tufts of leaves. The upper leaves ± keel-shaped. Winged ridges of stem undulately bent: Aculus acraspis

14b Upper leaf enlarged and curved, enveloping a cluster of disfigured leaves, less strongly pubescent and mainly enveloped by a larger leaf: Dasineura cytisi

15a Fruit galls => 18

15b Galls on single flower buds or on ± expanded parts of inflorescence => 16

16a Several up to all flowers disfigured => 17

16b Flower buds swollen, unopened, calyx swollen. Corolla and anthers aborted. 4–5 yellowish-white larvae. G. sagittalis: Dasineura sp.

16c Similar galls, contain jumping midge larvae. G. hirsuta, sagittalis: Contarinia sp.

17a Caused by gall midges. Usually only a part of the flower bud is galled. This is swollen, unopened; strongly pubescent, like the enlarged bracts. Larvae at first white, then pink-coloured. Genista spp.: Jaapiella genisticola

17b Caused by gall mites. Inflorescence distinctly shortened. Flowers largely leafy, with abnormal white pubescence. G. sagittalis: Aculus acraspis

17c Caused by gall mites. Flowers greened. G. tinctoria: Phyllocoptes genistae

18a No layer of mycelium inside fruit galls => 19

18b Fruit galls caused by midges, with layer of mycelium inside. Pod swollen, egg-shaped to cylindrical. Seeds aborted. Containing 1 (‒3) orange-red larvae. Genista spp.: Asphondylia genistae

= Similar gall on G. sagittalis is caused by Asphondylia bitensis. One to three red larvae, or pupae, in the galled pods. Inner wall of gall chamber lined with mycelium

19a On G. pilosa. The pods are of almost normal size but infestation is indicated by weak, discoloured tubercles. Larvae bone-coloured: Contarinia pulchripes

19b On G. tinctoria, sagittalis. The young pod is distinctly swollen and often remains hidden in the hypertrophied, unopened flower. Containing a single larva: Tychius parallelus

= Swollen pods may be caused by weevil larvae of Exapion difficile and E. genistae; it is not known whether these are true galls

Last modified 30.iv.2020