Plant Parasites of Europe

leafminers, galls and fungi

gallers on Cirsium

Dichotomous table for gallers on Cirsium

by Hans Roskam

1a On above-ground organs => 3

1b On roots => 2

2a Lateral roots with nodule-shaped, 2–3 mm across. C. arvense, oleraceum: Meloidogyne hapla

2b Main root or basal stem part with spindle-shaped swelling, up to 50 mm long and 10 mm thick. Contains a single larva. C. arvense, oleraceum, vulgare, etc.: Cleonis pigra

= The slightly cecidogenic caterpillar of Epiblema scutulana in stems and roots of various Asteraceae might also be responsible for root galls on Cirsium

3a On capitula or florets => 30

3b On stems or leaves => 4

3c Stems and leaves with white blisters, sometimes crust-like. C. oleraceum:
Pustula obtusata

4a Malformations restricted to single plant parts or to parts of shoots => 6

4b Malformations of expanded shoot parts of entire plants => 5

5a Plant completely stunted, ± disfigured; with expanded, or merely local, pale green, spongy swellings on all parts. C. arvense, oleraceum, tataricum: Ditylenchus dipsaci

5b Complete plant etiolated; development initially proceeding, later on stunted. Rosette leaves distinctly erect, lanky, usually non-flowering. Leaf blades narrowed, pale green, less spiny, occupied on both sides by many, sweet smelling widely distributed honey-yellow pycnidia, which are followed by initially reddish-brown uredinia and later on by black brown telia; only on C. arvense:
Puccinia punctiformis

6a Malformations exclusively or mainly on leaves => 10

6b Malformations predominantly on stems => 7

7a Swellings ± slender spindle-shaped => 8

7b Main- or side shoots with large, rotund or oblong multi-chambered swellings, about 10–50 mm long and 5–20 mm thick, initially green and succulent, later browned and woody. Each chamber contains a single larva. C. arvense, scattered on C. oleraceum: Urophora cardui

7c Facultative malformation of stem. Cirsium spp.: Ceratapion carduorum

8a Stem with extensive malformations => 9

8b Knob-like thickenings on root collar or on higher situated branchings. C. vulgare: Acanthiophilus helianthi

= All-sided, 10 cm long, inconspicuous stem swelling above the ground. Containing many amber-coloured puparia of an unidentified dipteran. Presumably a gall-like stunting caused by the larvae of a leafminer belonging to Melanagromyza

9a Stem terminally ± stunted and slightly thickened; tip of shoot stunted, closed. The pith contains a greenish, black-headed caterpillar. C. arvense, vulgare: Unidentified lepidopteran

9b On C. palustre. Swelling just below a clustered group of stunted capitula, containing a dirty red caterpillar: Epiblema scutulana

9c Stem over extensive parts usually spongy and swollen on one side, and sometimes distinctly curved. Galls with ± rugose surface, pale green; predominantly either close to the ground or close to the inflorescences. Cirsium spp.: Ditylenchus dipsaci

= The weevil Ceutorhynchus litura causes a malformation of 30–40 mm long on stem which becomes hardened and inflated, containing up to 12 larvae

10a Malformations with fungi fruiting on the outside => 28

10b Malformations caused by fungi fruiting on the inside of the galls, or caused by animal inducers => 11

11a Malformations of leaf margins or of leaf blades => 15

11b Malformations of the venation, sometimes ± widely extending into the unrolled leaf blade => 12

12a Galls restricted to the venation => 13

12b Main- or lateral veins to varied extents spongy, swollen and discoloured pale green together with their additionally sometimes ± clustered, also curled, surroundings. Cirsium spp.: Ditylenchus dipsaci

13a Main venation with ± extensive spindle-shaped swellings, situated predominantly on the leaf blade => 14

13b Midrib of the basal half of the rosette leaves slightly swollen. One to several larvae inside, tunnelling, more rarely mining. C. palustre, vulgare: Phytomyza continua

14a Galls spindle-shaped, usually brighter rimmed, with a single larva inside; gall rapidly collapsing and browning after the larvae have departed. C. arvense, tataricum, oleraceum, palustre, vulgare: Unidentified gall midge

14b Spindle-shaped bulges, about 2–12 mm long, yellowish to bright green, compact, glabrous, ± vitreous, sometimes in rows situated on the underside of the leaves; occasionally many small bulges on the basal stem parts. Sporulating close to the vascular bundle. C. oleraceum: Protomyces cirsii-oleracei

15a Leaves with either many, sometimes coalescing, hardly 1 mm long warts, or with very narrow rolls of the leaf margin => 24

15b Leaf blades with different malformations => 16

16a Extended malformations caused by aphids or cercopids => 20

16b Galls caused by other inducers => 17

17a Leaf blade with many small depressions or with pustule-shaped galls => 19

17b Leaf blades with irregular curls or folds => 18

18a Leaf margin ± folded or rolled, on the underside with several groove-like depressions, at first with a flat froth-covered nymph; leaf tip also folded, curled, or rolled. C. arvense, helenioides, oleraceum, etc.: Trioza viridula

18b Similar galls, on C. arvense, erisithales, heterophyllum, oleraceum, palustre: Trioza cirsii

18c Downward leaf roll, loosely undulate curled and tuberculate on the upper side. Leaf blade uneven, sometimes additionally with hairs. C. arvense, oleraceum: Trioza agrophila

19a Leaf blade with small depressions on the underside, with corresponding elevations on the upper side. C. helenioides: Trioza viridula

19b Leaf blade with green pustules. Containing a single midge larva. C. helenioides: Unidentified gall midge

20a Malformations caused by aphids => 21

20b Leaf blade, according to size, partially or completely and variously contracted; locally strongly curled and dark green. Infestation of young stems results in stunting, bending and clustering of neighbouring ± curled leaves. Cirsium spp.: Philaenus spumarius

21a Malformations caused by brown-black to dull black aphids => 23

21b Aphids yellow or dark red-brown => 22

22a Malformation of leaves caused by yellow aphids living on the underside. C. tataricum, oleraceum: Capitophorus horni

22b Aphid large, about 4 mm long, dark red brown, with transverse rows of black dots. Leaf blade curled, rolled, sometimes more densely haired. Heavier infestation may result in conspicuous stunting of young shoots. C. arvense, oleraceum, palustre, rivulare, vulgare: Uroleucon cirsii

23a Aphids about 1.5 mm long, brown-black, slightly powdered. Antennae half the body length. Siphunculi short, conical, slightly longer than cauda. Leaves rolled upward. C. oleraceum. pannonicum, ? canum: Aphis cirsiioleracei

23b Aphid about 2.5 mm long, dull black, rarely brown-black; antennae half the body length; siphunculi longer than the cauda. Affected leaves ± curled and bent downward. Strongly infected shoots variously stunted. Malformations not specific for the inducer. Following species host alternating, only distinguished by microscopical characters. Cirsium spp.:

a Aphis fabae s.s.

b Aphis fabae subsp. cirsiiacanthoidis

c Aphis fabae subsp. evonymi

24a Galls wart-shaped, consisting of several cells => 26

24b Roll of leaf margin => 25

25a Leaf margin narrowly rolled upwards and inwards. Larvae yellowish. C. oleraceum: Unidentified gall midge

25b Leaf margin narrowly rolled downwards and inwards. C. oleraceum:
Unidentified gall mite

26a Warts of conspicuous colour; content of nutritive cell yellow to red => 27

26b Content of nutritive cell colourless. Warts compact, vitreous green, pearl-like, often in large numbers on the underside of the leaves; sometimes coalescing into crystalline crusts. C. oleraceum: Synchytrium globosum

27a Galls compact, golden-yellow translucent; many on the underside of the basal leaves, scattered or ± coalescing. C. helenioides, oleraceum: Synchytrium aureum

27b Galls compact, reddish; on the underside of the rosette leaves, often coalescing into expanded yellowish- to blood red crusts. C. palustre: Synchytrium sanguineum

28a Sori with brown spores => 29

28b Sori with aecia, often several on the leaf underside, ± yellow or reddish margined; sometimes with oblong-oval shape on the major veins and only here facultatively inducing minor swellings. Cirsium spp.: Puccinia dioicae

29a Leaf blade on the underside with many small uredinia and telia. Fungus with two kinds of uredinia. The primary uredinia, accompanied by pycnidia, develop on the venation, sometimes on slight, bulge-like swellings. Cirsium spp.: Puccinia calcitrapae

29b Leaf blade with conspicuous sori, up to 5 mm wide, rotund, compact, initially yellowish-white, on the underside often clearly arched, soon coalescing bearing telia. Galls facultative. Cirsium spp.: Puccinia cnici-oleracei

30a Malformation primarily of receptacle. The gall causers are inside the host tissue => 34

30b Malformations of capitula or florets => 31

31a Capitula or florets hardly transformed => 32

31b Capitula usually enlarged, more rarely stunted, hardened, receptacle fleshy thickened. Florets greened or leafy. C. arvense. ? vulgare: Aceria anthocoptes

= Symptoms on capitula were also attributed to phytoplasma

32a Flower parts stunted or only slightly changed; malformations merely the results of inhibition rather than of gall induction => 33

32b Florets disfigured and discoloured; pistil thickened and lengthened, extending well above the florets. Containing red larvae. C. vulgare: Jaapiella compositarum

33a Florets stunted predominantly on one side of the ± twisted flower head. C. acaule, arvense, vulgare: Jaapiella cirsiicola

33b Capitula slightly stunted; florets hardly disfigured. Contain red larvae. C. arvense: Macrolabis cirsii

= Larvae of several gall midge species live between the aborted achenes on the receptacles of ± disfigured capitula of several Cirsium– and Carduus species. They hibernate in the decaying receptacles

33c Capitula with up to about 30 unilocular galls, 3 mm in across, with hard, lignified walls. C. ukranicum, also on Onopordum sp.: Isocolus cirsi

34a Larvae in or on the receptacle => 35

34b Capitula in the beginning ± spherically swollen, soon stunted and initially dark-violet, later brown, filled with dusting of spore balls. C. arvense, dissectum, helenioides, oleraceum, palustre, vulgare, etc.: Thecaphora trailii

35a Malformations caused by larvae without conspicuous head capsule => 36

35b Capitula almost normally developed. Receptacle somewhat thickened and hardened, contains one to several white larvae of snout beetles with brown heads, eventually also attacking the ovaries. C. arvense, dissectum, oleraceum, palustre, etc.: Larinus planus

36a Larvae cylindrical, with hook-shaped black mandibles; tephritid maggots => 38

36b Larvae slender, ± flattened, without conspicuous mandibles but with sternal spatula; gall midge larvae => 37

37a Receptacle swollen, hard, several chambers, containing red-yellow larvae. C. palustre, ? acaule: Unidentified gall midge

37b Capitula poorly developed, often oblique and twisted; stalks bent and buckled; flowers partially remaining closed; receptacle slightly swollen; several orange-red larvae. C. dissectum: Jaapiella cirsiicola

= Receptacles of many Asteraceae, especially in ± disfigured and stunted capitula of Cirsium- and Centaurea-species contain orange-red larvae of the saprophagous gall midge Clinodiplosis cilicrus. They invade hibernating and decaying receptacles which are earlier infected by other gall causers.

38a Receptacle completely or partially swollen => 39

38b Receptacle together with ± expanded parts or bearing stalks transformed into a slender, barrel-shaped, multi-chambered tough gall; florets completely withered. C. arvense: Urophora cardui

39a On C. eriophorum, erisithales, helenioides, etc. => 41

39b On C. vulgare, etc. => 40

40a Receptacle distinctly swollen, hardened, with several perpendicular oblong-oval chambers. Each chamber contains a single larva. Cirsium spp.: Urophora solstitialis

40b Receptacle thickened, hardened; containing several larvae. Urophora stylata

40c Furthermore in flower head galls of C. vulgare: Chaetorellia jaceae

40d Occasionally reported malformation of receptacles of Cirsium species. Larvae white with brown head capsule; black unsegmented pupal cocoons: Rhinocyllus conicus

41a On C. erisithales, helenioides, oleraceum => 21

41b On C. eriophorum. Receptacles often with several tough galls of different size, sometimes ± laterally coalesced and may expand over the whole receptacle. Many, usually perpendicular oblong-oval chambers, each containing a single larva: Urophora eriolepidis

41c In flower heads of C. eriophorum, spinossimum, vulgare: Urophora terebrans

42a Receptacle distinctly swollen, hardened. Containing several larvae: Tephritis conura

42b Receptacle conspicuously swollen, hardened, with several upright larval chambers. C. erisithales: Urophora congrua

42b Five more tephritid flies have been recorded from flower heads, viz., (1) Tephritis acanthiophilopsis from C. canum; (2) T. cometa from C. arvense, palustre, vulgare; (3) Terellia ruficauda from C. arvense; (4) Terellia longicauda from C. rivulare; (5) Terellia serratulae from C. vulgare, also on Carduus; all not true gall causers.

Last modified 24.viii.2020