Plant Parasites of Europe

leafminers, galls and fungi

gallers on genus Scabiosa

Dichotomous table for gallers on Scabiosa

by Hans Roskam

1a On parts above ground => 2

1b Roots with small cylindrical-spindle-shaped swellings, 3–4 mm long, and considerable formation of side roots: Meloidogyne hapla

2a Malformations of inflorescences or flowers => 11

2b Malformations on vegetative parts => 3

3a On leaves, shoot tips or stems => 4

3b Many buds on root collar develop into short, laterally and variously growing, ± clustered stump-like, succulent shoots: Aphelenchoides fragariae and/or Rhodococcus fascians

4a Malformations on leaves, with or without inclusion of tips or axial parts of shoots => 7

4b Galls on axial parts of shoots => 5

5a Inducers inside galls => 6

5b Stem locally stunted, with irregular spindle- or bulge-shaped swellings and often strongly distorted or irregularly bent, up to a right-angle; often with several rimmed depressions which contain scale insects below scales. S. ochroleuca: Planchonia arabidis

6a Shoot axis, especially at base, with nodular, succulent, dark red-brown swelling. Containing a caterpillar. S. atropurprurea, canescens, columbaria, ochroleuca, triandra: Alucita grammodactyla

6b Axial parts of flowering shoots with oblong-oval swelling, up to 4 mm long, often ± crimson-red. Containing a pale-yellow caterpillar with yellow-brown head. S. atropurprurea, canescens, columbaria, ochroleuca, triandra: Alucita grammodactyla

7a Galls with abnormal, ± white pubescence => 10

7b Malformations lacking conspicuous pubescence => 8

8a Malformations caused by aphids => 9

8b Leaves terminally on vegetative shoots ± distinctly clustered. Leaf blades narrowed and ± with protuberances. Scabiosa spp.: Aceria squalida

9a Shoot axis variously stunted. Leaves curved and curled. S. columbaria, ochroleuca, triandra: Aphis thomasi

9b Similar malformations. S. atropurpurea, columbaria, ochroleuca, triandra: Aphis confusa

10a Leaves sometimes densely clustered on tips of non-flowering sometimes stunted main and side shoots; leaf blades narrowed, rolled upwards, ± weaved and tuberculate, especially stunted basally and over often larger expansion ± densely white felt-like pubescent. In strongly infected plants also white erinea also locally on sometimes strongly swollen leaf- or stem parts. Also inflorescences may be severely stunted and white felt-like over large expansion. Scabiosa spp.: Aceria squalida

10b Inside leaf rosette two or more leaves remain erect. Their base is stunted, and severely stunted leaf blades are swollen, mussel-like, thickened and at least the basal part on both sides densely covered with long, white hairs, resulting in a compact gall. Sometimes with similar galls on lateral buds or tips of severely stunted shoots. Containing several white, later on ± reddened larvae. S. columbaria: Jaapiella scabiosae

11a Malformations lacking conspicuous additional pubescence => 12

11b All parts of still young, ± stalked capitula severely stunted and often densely pubescent. Exceptionally also further developed inflorescences affected, of which almost only the involucral bracts are ± disfigured and densely haired. Scabiosa spp.: Aceria squalida

12a Malformations caused by animals => 14

12b Malformations caused by fungi => 13

13a Anthers, sometimes also filaments, ± shortened and swollen, soon filled with dirty straw-coloured spore masses. S. columbaria & subsp. balcanica, lucida, ochroleuca, triandra: Microbotryum intermedium

13b Flowers variously stunted or distorted; sometimes with ± petal-like transformed anthers. Diseased parts soon covered with a loose, dark down of branched conidiophores. S. columbaria, lucida, ochroleuca: Peronospora violacea

14a Malformations of almost entire flower head => 15

14b On ± fully developed capitule, single to many involucral bracts are distinctly elongated, thread-like, rolled upwards, not additionally pubescent and often bumpy and curved. Also some greened receptacular bracts and even sexual organs may be similarly galled. Scabiosa spp.: Aceria squalida

15a Malformation of complete flower head. Flowers greened, ± stalked, and developing new shoots (phyllanthy). Scabiosa spp.: Aceria squalida

15b Flowers unopened, swollen. Containing several jumping midge larvae. S. columbaria: Contarinia scabiosae

Last modified 18.xi.2023