Plantparasieten van Europa

bladmineerders, gallen en schimmels

gallers on Tragopogon

Dichotomous table for gallers on Tragopogon

by Hans Roskam

1a On plant parts situated higher above-ground => 4

1b On roots, root collars or basal stem parts => 2

2a Galls on root collar or on neighbouring stem parts => 3

2b Roots with bulging, chambered swellings. Each chamber containing one larva. T. porrifolius: Aulacidea hieracii

= On T. porrifolius the eelworm Meloidogyne hapla has been recorded

2c Swelling on roots of T. porrifolius, pratensis: Orellia falcata

3a Root collar or basal stem parts with one-chambered, rotund, sometimes isolated, one-sided, succulent tough-walled swellings, or galls often in groups or rows coalesced into ± bumpy tubercles or even into several cm long, irregular bulges. In each rotund- oblong-oval 1–1.5 mm long larval chamber is one whitish larva. T. dubius & subsp. major, porrifolius, pratensis & subsp. orientalis: Aulacidea tragopogonis

3b Conspicuous, 2.5–3.5 x 4–5 cm large, rotund to oblong-oval, succulent proliferations on root collar, undulate on the surface. T. porrifolius: Agrobacterium tumefaciens

4a On capitula, florets or achenes => 10

4b Localised or elongate malformations on leaves or shoots, sometimes extending into the green parts of the inflorescence => 5

5a Malformations with sporulating fungal sori on the surface => 9

5b Malformations caused by animal inducers => 6

6a Malformations predominantly developing on leaves => 7

6b On the base of the main stem, one-sided brown-yellowish multi-chambered swelling. T. dubius & subsp. major, porrifolius, pratensis & subsp. orientalis: Aulacidea tragopogonis

7a Inducers inside the galls => 8

7b Leaves sometimes ± twisted, curled; also the sheaths abnormally inflated. T. crocifolius, dubius, porrifolius, pratensis & subsp. orientalis: Brachycaudus tragopogonis

7c Malformations have been recorded caused by froth-covered nymphs. T. orientalis: Philaenus spumarius

8a Leaf blade with several slight swellings, separated from each other and therefore inconspicuous, about 1 x 2 mm long, situated between the veins. Each containing a larva. T. pratensis: Unidentified gall midge

8b Basal leaves with petioles and basal leaf blades distinctly shortened, pale green, in ± expanded areas swollen, spongy-undulate; other parts of leaf blade ± stunted. T. pratensis: Ditylenchus dipsaci

9a Shoots over large parts ± disfigured and etiolated, often remaining sterile. Leaves narrowed, ± shortened, pale green; like the stem occupied with many distantly, honey-yellow spermogonia and white margined, orange-red aecia. Infestation also occasionally extending into similarly deformed involucres and even into achenes. Tragopogon spp.: Puccinia hysterium

9b Similar malformations on T. dubius, porrifolius, pratensis & subsp. orientalis: Puccinia brachycyclica

9c Oblong-oval sori, initially closed and porcelain-glossy, later breaking open and with mealy dusting, occur rather often on all green parts and induce excessive branching and other malformations on early affected developing buds. Tragopogon spp.: Pustula obtusata

10a Malformations on capitula => 12

10b Galls on single or several florets, especially on achenes of capitula that look normal from the outside => 11

11a Basal part of the achene transformed into a mustard seed-like gall, large, thin- and hard-walled, one-chambered. Containing a single larva. T. pratensis: Unidentified gall wasp

11b chene spindle-shaped, swollen. T. pratensis: Unidentified gall midge

12a Capitula greened or disfigured by fungi which later produce dusting of spores => 15

12b Malformations caused by animal inducers => 13

13a Malformations caused by fly maggots or midge larvae => 14

13b Capitula remaining closed. Florets ± atrophied, embedded by a bladder-like malformation, swollen, conspicuously cornicular converging, one-sided enclosed by involucral bracts. T. pratensis: Cause unknown – cf. Brachycaudus tragopogonis

14a Capitula remaining closed; slightly swollen at base, variously disfigured and curved. Containing several whitish to yellow jumping larvae. T. dubius, pratensis: Contarinia tragopogonis

14b Hardly conspicuous, often one-sided malformation of the flower head caused by single larvae, usually living between the achenes. T. pratensis: Ensina sonchi

15a Developing capitula shortened, ± globular to broad oval, swollen. Flower parts soon to a large extent affected by blackish-dark violet discolouration, later with dusting of spore masses. Tragopogon spp.: Microbotryum tragopogonis-pratensis

15b Malformation and ± greening of all florets in a flower head. T. pratensis subsp. orientalis: Cause unknown – ? gall mite

Laatste bewerking 27.iv.2020