1a On above-ground parts => 2

1b Roots with nodule- to spindle-shaped swellings. Crepis spp.: Meloidogyne hapla

1c Rounded root galls 4–5 mm long on Aetheorhiza bulbosa: Entyloma crepidicola

2a Malformations of capitula => 28

2b Galls on vegetative parts => 3

3a Malformations with fruiting bodies of fungi on the outside => 21

3b Malformations caused by animals or by fungi whose fruiting bodies develop inside the galls => 4

4a Galls exclusively or predominantly on the stems => 18

4b Galls only or mainly on leaves => 5

5a Galls especially on midrib and main veins, only secondarily on leaf blades => 13

5b Galls largely extended over the leaf blades-, or local, induced by psyllids, gall midges or gall mites and fungi => 6

6a Malformations of undefined shape, extending over the whole leaf blade => 12

6b Galls of ± defined shape and size => 7

7a Malformations with abnormal pubescence => 11

7b Galls glabrous or without supplementary pubescence => 8

8a Galls only about 1–3 mm long, wart- or callus-shaped => 9

8b Leaf blade usually with several rotund, up to 4 mm wide, pale green, often yellowish or reddish bordered pock-shaped upward bulges. Galls only closed by the epidermis beneath, a red-yellow larva showing through. C. biennis, conyzifolia, praemorsa, Aetheorhiza bulbosa, etc.: Cystiphora sp.

9a Galls pearl-like, often very many on the underside, sometimes also on upper side of the rosette leaves, hardly 1 mm long, red- to golden yellow translucent. Occasionally also occurring on leaf veins and petioles and below on the stem; sometimes forming crusts or bars resulting in further malformation of the plant parts => 10

9b Leaves with rotund, 1–3 mm wide, slightly protruding yellow-grey bulges. C. biennis, rubra: Entyloma crepidis-rubrae

10a On C. biennis. Leaf blades with pearl-like, compound galls, often aggregating into extended, orange-yellow, or blood-red crusts: Synchytrium taraxaci

10b On C. alpestris, biennis. Orange- to golden yellow multicellular warts: Synchytrium aureum

11a Protrusions of the leaf underside with erineum. C. paludosa: Unidentified gall mite

11b Similar malformation, in connection with narrow, abnormal pubescent marginal rolling, usually only short upwards stripe. C. praemorsa: Unidentified gall mite

12a Leaf blades of basal leaves sometimes with several dimple-shaped depressions on the underside, each dimple with one larva. Leaf blades, which are occupied by many older larvae, are deformed and have deflected, often ± twisted, margins. C. biennis: Craspedolepta flavipennis

12b Malformation of the leaf blades by aphids: Nasonovia ribisnigri

12c Leaf blade apex and margins nest-like downwardly curved, especially close to the site of attack strongly curled and dark green. Infestation of stem is accompanied by localised stunting and curving of the stem, which bears 2–3 closely situated bent and curled leaves. C. biennis, pyrenaica, paludosa: Philaenus spumarius

13a Extensive galls on the midrib, often already emerging from leaf base => 16

13b Galls on other sites, not connected with the leaf base => 14

14a Nodule- or bulge-like, massive galls on the veins, without a central chamber, the inside with fungus spores => 15

14b Midrib with pale spindle-shaped swelling; one larva inside. C. biennis: Unidentified gall midge

15a Galls predominantly on leaf tips. Infected parts initially yellowish, brown-red later on; often bladder-like swelling on upper side; veins also swollen, especially protruding on underside, often conspicuously reddened. Spores in vascular tissue. C. biennis: Protomyces crepidicola

15b Nodule-like, chocolate-brown swellings on the main- and midribs of the leaves, as well as more bulged swellings of the basal stem parts. Spores in and next to the vascular bundles. C. paludosa: Protomyces crepidis-paludosae

15c Leaf galls on C. froehlichiana subsp. dinarica. Bulges about 0.5–0.75 mm wide, ± grey-yellow, protruding hemispherically on the underside, often many per leaf blade: Protomycopsis crepidis

16a Midrib at its base up to three times its normal size, swollen. Gall gradually narrowed to mid-leaf, or further, swelling not extending to the sometimes nested leaf blade parts. Contains a maggot inside => 17

16b Midrib of several, often severely stunted rosette leaves, including adjacent leaf blade parts usually spongy, swollen, pale green, sometimes, ± reddened. Many eelworms inside. C. biennis, capillaris, paludosa, tectorum: Ditylenchus dipsaci

17a Rosette leaves, more rarely stem leaves, mined. C. biennis: Phytomyza robustella

17b Similar galls, mainly in basal leaves of C. paludosa: Phytomyza araciocecis

18a Galls glabrous, tough-walled. Contain larvae => 19

18b Galls spongy, pale green, with ± rugose surface. Very differently extending, even many cm long. Stem swollen on all sides, or more one-sided; internodes often strongly shortened, spirally twisted, curled or bent. Infestation especially on the basal leaf parts; occasionally also to a different degree in the swollen, ± nodding and closed capitula. C. biennis, capillaris, foetida subsp. rhoeadifolia, taraxacifolia, etc.: Ditylenchus dipsaci

19a wellings close to the stem base => 20

19b Stem with ± spindle-shaped swellings, about 10–40 mm long and 6–15 mm broad, sometimes multiple hunchbacked, also bent. Galls on main stems of C. biennis often united to 15 and more cm long, ± large chambered swellings. Inside the greatly enlarged pith are many, lateral- or central compact-shelled larval chambers. One larva per chamber. C. biennis, capillaris, tectorum: Aulacidea sp.

19c Similar galls are also described from C. paludosa, taraxifolia: Phanacis lusitanica

19d Corresponding galls on C. pulchra: Phanacis rufipes

20a Stem bases of young plants stunted, swollen to a different extent, with ± reduced and mutually close leaves. In the swollen pith is a boring maggot. C. capillaris: Napomyza lateralis

20b Basal part of stem, including root collar severely shortened and swollen; occasionally bent, partially bushy (phyllanthy). Several white larvae inside. C. setosa: Unidentified beetle

21a Malformations with spores of rust fungi => 23

21b Malformations caused by other fungi => 22

22a Internodes shortened, plant very bushy; development of flowers stunted in strong infestations; stem and leaves irregularly curved, with small spore-bearing pock-like depressions. C. biennis, capillaris: Didymaria matricariae

22b Leaf blade initially with dark green, later on yellowish, ± vesicular swellings, showing grey-white layers of asci after ripening. C. conyzifolia, mollis, pygmaea, pyrenaica: Volkartia rhaetica

23a Fungus host alternating, on Crepis only producing aecia and pycnidia. Sori sometimes slightly blistered, swollen => 27

23b Fungus host-specific, all spore types developing on Crepis; gall-like malformations only by the aecidial stage with thickened inner wall of the peridium => 24

24a Aecia-producing mycelium locally, sori facultatively blistered, swollen => 26

24b Aecia-producing mycelium extending over large areas within the usually sterile host; cups scattered, usually occurring on all leaves of the host => 25

25a Whole plant changed. Diseased leaves upright, often narrowed, thickened, abnormally pale; on the underside and partially also upperside, with many aecia and pycnidia. Infected stem ± swollen, initially taller than the healthy ones, pale green, often remaining sterile. C. capillaris, tectorum, etc.: Puccinia crepidis

25b Pycnia and aecia on C. aurea: Uredo breventiaca

25c Pycnia and aecia on C. foetida incl. subsp. rhoeadifolia: Puccinia barkhausiae-rhoeadifoliae

26a The closely situated aecia in yellowish, sometimes red margined bulge-like swellings. These are rotund on the leaf underside and oblong on the veins and stems. Intensity of gall formation depends upon interaction of host and parasite. Basic differences between the malformations caused by the following species are absent. Wall cells of the pseudo-peridium in irregular rows, the inside thickened. Uredinia and telia not cecidogenic, in small sori, widely distributed on leaves and stem. Fungi differ in microscopic characters, especially if telia are present and largely according to the host. Stages with pycnia and aecia are facultatively cecidogenic:

a On C. biennis: Puccinia praecox

b On C. paludosa: Puccinia major

c On C. alpestris: Puccinia alpestris

d On C. aurea: Puccinia crepidis-aureae

e On C. pyrenaica, also on alpestris, capillaris, tectorum: Puccinia crepidis-blattarioidis

f On C. conyzifolia: Puccinia crepidis-grandiflorae

g On C. foetida, taraxifolia, etc.: Puccinia crepidicola

h On C. jacquini: Puccinia krupae

i On C. mollis: Puccinia crucheti

j On C. [Intybus] praemorsa: Puccinia intybi

k On C. pygmaea: Puccinia crepidis-pygmaeae

l On C. sibirica: Puccinia crepidis-sibiricae

27a Sori often bright yellow, sometimes red margined, not- or only slightly thickened. Usually freely situated on the leaf blade, rotund, on the underside slightly bulging, on the upper side slightly depressed and occupied with spots of brownish pycnidia; the aecia on the underside with well-developed pseudoperidia, which open cup-shaped, their cells in regular rows and thickened on the outside. C. biennis, more rarely C. capillaris, taraxacifolia, vesicaria: Puccinia opizii

27b Cushions on the leaf blade more distinctly bulged; pycnia and aecia mainly on the venation, possibly on petioles and even on stems. C. biennis: Puccinia silvatica

28a Capitula greened and leafy, with a multiplication of flower peduncles supporting small malformed capitula (phyllanthy => 31

28b Capitula stunted, weakly thickened, remaining closed => 29

29a Malformations by gall midge larvae => 30

29b Malformations by fly maggots. C. biennis: Noeeta crepidis

29c Capitula swollen, peduncles swollen just below the flower head; stems also swollen if attacked in rare cases. C. taraxacifolia: Ditylenchus dipsaci

30a Several yellow, jumping larvae occur in the basally weakly thickened and twisted capitula. C. biennis, etc.: Contarinia hypochoeridis

30b Malformed capitula with pale, non-jumping larvae. C. paludosa: Unidentified gall midge

31a Capitula, often in large numbers per plant, completely deformed, sometimes partially developing into further, similarly deformed reduced capitula. Involucre often not changed, corollas severely stunted and ± greened; anthers and ovaries changed into green, ± leafy structures. C. biennis, capillaris, tectorum: Aceria rechingeri

= The gall mite Phyllocoptes oligostictus is inquiline in enlarged flower heads of C. biennis caused by Aceria rechingeri

31b Capitula almost witches’ broom-like, sometimes even repeatedly developing into stalked smaller capitula; flowers often hardly, sometimes unrecognisably deformed though with ± lanceolate, leafy structures instead. Usually all capitula of a host are similarly deformed. C. biennis, tectorum: Inducer unknown