Plant Parasites of Europe

leafminers, galls and fungi

gallers on genus Thalictrum

Dichotomous table for gallers on Thalictrum

by Hans Roskam

1a On plant parts above ground => 2

1b Roots with slender spindle-shaped swellings, up to 5 mm long. T. aquilegiifolium, simplex: Meloidogyne hapla

2a On inflorescences, flowers or fruits => 17

2b On stems, shoots and leaves => 3

3a Malformations mainly on stem, or usually involving many severely stunted leaves, clustered at shoot tips, or extending over many leaflets of largely disfigured leaves => 12

3b Galls mostly on unfolded leaves; locally restricted, usually wart- or spindle-shaped. Caused by fungi => 4

4a Galls several mm long, in the leaf blades ± rotund, protruding on underside; on leaf veins, -midrib, -stalk, or flower parts spindle-shaped to oblong-oval. Bulges with sori of black telia or with densely positioned, yellowish aecia => 5

4b Galls wart-shaped, multi-cellular, up to 1 mm long, golden-yellow; single or ± coalescing, usually on underside of basal leaves, also on axis, stalks and basal stem parts. T. alpinum, flavum, lucidum, simplex, squarrosum: Synchytrium aureum

5a Bulges on leaves usually downwardly arched and predominantly only there bearing aecia; on upper side usually ± depressed, partially bearing spermogonia, often ± crimson to violet-red margined => 6

5b Sori on leaf underside, also on stem; of variable size, often conspicuous, slightly arched, black, weakly glossy, compact. T. alpinum: Puccinia rhytismoides

6a Aecia densely positioned, in smaller or larger groups on underside of ± arched bulges. Several, especially biologically different rust fungi, alternating on grasses, indistinguishable by their galls and usually also by the microscopic morphology of their aecia => 8

6b Aecia positioned loosely => 7

7a Aecia positioned on expanded, thickened, often dark violet discoloured spots, usually on both sides. Peridium usually with deflected border. Spermogonia develop rarely. T. alpinum: Puccinia septentrionalis

= On same host, with similar distribution, alternating on Agrostis, the rust fungus Puccinia recondita develops only in low number (8–12) in dense groups on underside leaf; aecia occur on discoloured, not noticeably thickened spots.

7b Aecia on often yellow-brown discoloured, hardly swollen leaf spots, protruding on underside, associated with honey-coloured spermogonia, developing on both sides. Peridium cup-shaped, with deflected, lacerate border. T. foetidum: Puccinia thalictri-koeleriae

8a Frequent fungi with aecia on several Thalictrum species => 11

8b More locally recorded fungi, which develop aecia on only a few species => 9

9a Aecia with several Thalictrum species as main host => 10

9b Aecia on T. foetidum as main host; in rounded groups on leaf underside, also occurring on fruits and in elongated patches on disfigured leaf midrib, -stalk and stem. Peridium cup-shaped or ± cylindrical, with lacerate white border: Puccinia thalictri-distichophylli

10a Aecia with cup-shaped or funnel- to tube-shaped peridium, at maturity with deflected, ± frayed border. T. aquilegiifolium, foetidum, minus: Puccinia poae-nemoralis

10b Aecia not further described, on T. aquilegiifolium, minus: Puccinia elymi

11a Aecia in smaller or larger groups on slightly thickened spots, often violet-brown on upperside, on underside yellowish and usually brown-bordered. Peridium cup-shaped, with deflected, frayed border. Thalictrum spp.: Puccinia alternans

11b Aecia and the often conspicuous spermogonia, positioned in a circle, usually developing on upperside on often distinctly swollen pads. Peridium whitish or yellowish with deflected, irregularly serrate or slightly fringed border. T. flavum, minus, simplex: Puccinia recondita species complex

12a Differently furnished malformations caused by animal parasites => 14

12b Malformations bearing early brown sori or exhibiting at first ± lead-grey bulges, with dusting of black spores later on => 13

13a Lead-grey swollen bulges, occurring on the often largely stunted leaf blades especially on venation protruding on both sides, often also on the ± bent leaf-midrib, -stalk, on stems and even flower parts. At first closed, later on erupting and with black dusting. Thalictrum spp.: Urocystis sorosporioides

13b Mycelium perennial, the developing host organs changing considerably. Shoots with lanky, elongated internodes, developing faster than normal ones. Leaf axis squat, leaf blade narrower and pale, diseased parts bearing many dark-brown telia. Thalictrum spp.: Tranzschelia anemones

14a Mainly curling or slightly swollen malformations of ± stunted leaves => 15

14b Leaflets curled, margin folded upwards, forming a subglobular gall of variable size. Containing several reddish larvae. T. speciosissimum: Dasineura bragancae

15a Malformations not conspicuously pubescent => 16

15b Up to 10 mm long, bud-like clustering of markedly stunted, ± whitish haired leaves on tips of main- and side shoots or in stunted axillary buds on the longitudinal growth. Larvae glossy red. T. aquilegiifolium, flavum, minus, simplex: Jaapiella thalictri

16a Malformations of terminal leaves and possibly of neighbouring inflorescences caused by midges or aphids => 17

16b Leaf blades of usually basal leaves on the ± stunted midrib converging. Leaflets shortened, mostly spoon-like, converging, thickened, strongly rugose and curled. T. flexuosum, minus: Phyllocoptes jaapi

16c A few internodes of apical part of stem stunted, bent when infestation is one-sided. Leaves and sometimes stem of the similarly stunted and disfigured inflorescence variously clustered. Leaf blades ± converging, curved and curled, dark green close to infestation site. Thalictrum spp.: Philaenus spumarius

17a On inflorescences or single flowers => 18

17b Fruit distinctly swollen, globular or acuminated, egg-shaped, up to 5 mm long, seeds absent; wall succulent, thickened; gall in dry condition ribbed. Containing one or two yellow larvae. T. aquilegiifolium, flavum, lucidum, minus incl. subsp . majus, simplex, speciosissimum: Ametrodiplosis thalictricola

18a Malformation of inflorescence or galls on single or clustered flowers; caused by animal inducers => 19

18b Expanded or localised malformations in the axis of the panicle, flower peduncles or perianth leaves caused by fungi => 5

19a Single flowers globularly swollen, stamens and especially anthers little developed; sometimes on shortened stalks and axis of panicle with several clustered in the otherwise normally flowering or already fruiting inflorescences. Larvae glossy red. T. aquilegiifolium, flavum, minus, simplex: Jaapiella thalictri

19b Inflorescence markedly stunted, densely occupied by disfigured, ± greened flowers. T. aquilegiifolium, alpinum, delavayi, flavum, lucidum, minus: Aphis thalictri

Last modified 18.xi.2023