Plant Parasites of Europe

leafminers, galls and fungi

gallers on Hieracium

Dichotomous table for gallers on Hieracium and Pilosella

by Hans Roskam

1a On inflorescences or in the capitula => 23

1b On vegetative parts => 2

1c Proliferations on the base of terminal rosettes on stolons. Pilosella spp.: Aulacidea subterminalis

2a On leaves => 8

2b On shoot axial parts or tips => 3

3a On shoot axial parts => 5

3b On shoot tips => 4

3c All parts of shoot with white crusty blisters, very variable in size; shoot often distorted. Hieracium and Pilosella: Pustula obtusata

4a Rosettes with many variously enlarged and thickened leaves at their centres, externally with abnormally felt-like pubescence, the leaf margins or leaf blade often ± cone-shaped converging. Several, initially white- to cream-coloured, later red larvae. Pilosella spp.: Macrolabis pilosellae

4b Terminal leaves of lateral and main shoots swollen, folded upwards, making a fleshy pouch, with outside often ± villous pubescent; mid- and basal veins, sometimes also the neighbouring stem parts, thickened and discoloured. Larvae yellow-white. Hieracium spp., exceptionally on Pilosella: Macrolabis hieracii

5a Inducers inside the galls => 6

5b The inducers are in bordered, hollowed depressions in small bulging swellings, solitary or many Hieracium spp., less on Pilosella: Planchonia arabidis

6a Tough, broadly protruding galls caused by gall wasp larvae => 7

6b Slim stem swellings caused by eelworms Spongy swellings in the stem, predominantly on species of Pilosella. Tissue fragile and necrotic, lacking larval cavities. Ditylenchus dipsaci

7a Shoot with rotund or barrel-shaped swelling, up to 40 mm long, multilocular, initially green, later brown, ± occupied with stiff-bristly white hairs. One yellowish-white larva per chamber. On many species of Hieracium; sporadically also on species of Pilosella: Aulacidea hieracii

7b Irregularly shaped, multilocular swellings of the stem, 2–2.5 x 1.5 cm in size; the galls are hardly lignified and can easily be opened. They ripen in autumn; adults emerge in the following spring. Hieracium sp.: Diastrophus hieracii

7c Similar, but smaller, 4–10 mm long, uni/bilocular swellings in the upper part of the shoot, also at the base of the flower head or below the leaf rosettes on stolons. Pilosella officinarum: Aulacidea sp.

8a Malformation predominantly situated on the leaf blade or leaf margin, usually without involving the midrib, sometimes with abnormal pubescence => 12

8b Galls in petioles or midribs, sometimes ± extending into the leaf blade => 9

9a Inconspicuous, usually yellow margined, 2–3 mm long, 1 mm wide swelling on the midrib; covered with brown fungus spores => 11

9b Tough walled or spongy, loose, galls with animal inducers inside => 10

10a Long-oval to spindle-shaped, woody swelling, with large central chamber, on the underside of petiole or midrib; up to 3.5 mm long and 1.5 mm wide, ± yellowish. Often several galls, in various ways connate. Containing a single yellowish-white larva. Pilosella cymosa, echioides, flagellaris, floribunda, officinarum, onegensis: Aulacidea pilosellae

= Larvae of Dasineura nervicola cause egg-shaped swellings on the mid-vein of Pilosella lactucella, officinarum. Very rare.

10b Irregular, spongy, pale green or red tinted massive swellings of various size extending from petiole or midrib to the leaf blade. Hieracium and Pilosella: Ditylenchus dipsaci

11a On Hieracium spp.: Puccinia hieracii

11b On Pilosella spp.: Puccinia hieracii var. piloselloidearum

12a Malformations of the leaf margin, curls or abnormal pubescence => 16

12b Pustules, grooves or warts on leaf blade, sometimes only slightly changed => 13

13a Rotund pustules, up to 6 mm long, often rimmed, bulging on the upper side; usually a few to many per leaf blade => 15

13b Warts or small grooves => 14

14a Less than 1 mm long, yellowish gleaming or coloured warts on the underside of the rosette leaves, usually many and variously coalescing into crusts or into stripes the stems. Pilosella officinarum: Synchytrium aureum

14b Leaf blade with small downward outgrowths. In case of heavy infestation both halves bent upward along the midrib. Hieracium racemosum; Pilosella officinarum, onegensis, piloselloides subsp. praealta: Trioza proxima

14c Similar malformations. Hieracium sp.: Craspedolepta flavipennis

15a Yellowish-green to intensively reddened pustules, many per leaf, occasionally coalescing, especially frequent on basal leaves on the underside between epidermis and parenchyma. Larvae reddish-yellow to dark orange-red, up to 2 mm long. Hieracium and Pilosella: Cystiphora sanguinea

15b Initially yellowish-white, later brown (never reddish) rotund, sometimes weakly swollen irregularly margined spots. Hieracium and Pilosella: Entyloma hieracii

16a Loose roll of the leaf margin or curls of the leaf blade => 19

16b Narrow leaf roll, often simultaneously developing with swellings, or only ± expanded erinea, of the leaf blade => 17

17a Expanded, compact upward rolling of the leaf margin => 18

17b Short, densely felt-like pubescent marginal bulge or –nodule, corresponding nodules also on the leaf blade; sometimes strong erinea on the upper side, also on the underside venation. Hieracium lachenalii, murorum: Eriophyes villificus

18a Only known from Pilosella officinarum: Aceria pilosellae

18b As well on Hieracium as Pilosella: Aceria longiseta

19a Malformation predominantly a marginal rolling of the leaf blade => 21

19b Malformation predominantly as a markedly curved, additionally curled leaf, or as a slight bulging of the same organ => 20

20a The shoot is stunted on one side and slightly thickened; in the affected area leaves are clustered, the leaf blades curved, variously twisted and curled, locally coloured intense green. Hieracium and Pilosella: Philaenus spumarius

20b Weak, merely facultative, not discoloured swellings of the leaf blade. Aphid straw yellow, green or reddish; apterous adults dorsally with dark spots. Hieracium and Pilosella: Nasonovia ribisnigri

21a Leaf margins rolled upwards => 22

21b Leaves rolled downwards or often curved and ± strongly curled. Usually several leaves on the shoot tip are conspicuously malformed. Hieracium spp.: Aphis hieracii

22a In spring on the upperside of the leaves which fold upwards to enclose the colonies, later feeding on stems and inflorescences. Hieracium and Pilosella: Nasonovia compositellae

22b In spring inside upwardly rolled leaves, later moving onto stems and flowers. Hieracium alpinum, lachenalii, murorum; Pilosella aurantiaca, officinarum, piloselloides: Nasonovia pilosellae

23a Receptacle of one- or several capitula deformed => 24

23b Stalks of complete inflorescences shortened, thickened and curved. In the axils of clustered leaves 2–3 pale orange-yellow larvae. The development of neighbouring capitula often markedly stunted. Hieracium umbellatum: Unidentified gall midge

24a Inducers develop in the receptacle => 27

24b Inducers develop between the involucral scales => 25

25a Malformations caused by gall midges => 26

25b Malformations caused by gall mites. Capitula ± semiglobular, flowers markedly stunted and greened, flowers occasionally variously developing further. Hieracium and Pilosella: Aceria longiseta

26a Capitula often extensively shortened, usually enlarged on all sides. Several yellow, jumping larvae. Hieracium lachenalii, prenanthoides, umbellatum; Pilosella caespitosa, flagellaris, officinarum; Tolpis staticifolia: Contarinia pilosellae

26b Similar malformations of capitula on Hieracium murorum; Pilosella officinarum caused by orange-red, non-jumping midge larvae: Jaapiella compositarum

27a Conspicuous larvae developing solitarily or gregariously in distinct cavities of the receptacle => 28

27b The turgid, usually unilaterally malformed receptacle consists of a spongy, uniform parenchyma containing many eelworms. Pilosella cymosa, officinarum: Ditylenchus dipsaci

28a Whitish or yellowish maggots, , lacking a distinct head capsule => 29

28b Larvae with thoracic legs and distinct head capsule occurring in clearly swollen capitula. Hieracium amplexicaule, lachenalii, murorum, prenanthoides, umbellatum: Hellinsia didactylites

29a Malformations caused by tephritid larvae with conspicuous mouthparts and eventually developing a puparium => 30

29b Malformations caused by cynipid larvae, white. Hieracium lachenali: Aulacidea nibletti

30a Flower heads distinctly swollen at base, not opening, not conspicuously hardened; clearly curved if infected on one side; usually all capitula of a panicle infected. On many Hieracium and Pilosella species. Noeeta pupillata

30b Larvae in hardly disfigured flower heads. Pilosella lactucella, officinarum: Tephritis ruralis

30c Ditto. Hieracium murorum, sabaudum: Trupanea stellata

Last modified 24.viii.2020