Dichotomous table for gallers on Rumex

by Hans Roskam

1 On parts above ground => 9

1b On roots, rhizomes or root collar => 2

2a Rotund to spindle-shaped swellings containing causers in well-defined chamber or tunnel => 5

2b Galls compact, lacking chambers or feeding tunnels => 3

3a On roots => 4

3b Conspicuous, at first whitish, later on browned, succulent proliferations on root collar, eventually decaying. R. acetosella: Agrobacterium tumefaciens

4a Roots with slender spindle-shaped swellings, up to 7 mm long, sometimes bearing side roots. R. acetosella, crispus: Meloidogyne hapla

= Among the cyst developing Heterodera species, which cause development of giant cells inside roots, H. schachtii has been recorded

4b Expanded, globular, tuberous or ± barrel-shaped proliferations on roots, up to 20 mm thick and 30 mm long, which originate from enlarged and multiplied host cells. In cavities, together with many thick- and brown-walled, globular perennial spores, up to 46 µm large. R. scutatus: Physoderma ruebsaamenii

5a Swellings oblong or rotund, with single to several larval chambers => 6

5b Oblong, irregular expanded swelling on root, up to 15 mm long or more. Feeding tunnel elongate; containing a slender, dirty-white caterpillar with dark dorsal stripe and black-brown head. R. acetosella: Pyropteron triannuliformis

6a Galls more than 10 mm long, usually multi-chambered => 8

6b Galls only rarely up to 10 mm long, usually one-chambered => 7

7a Rotund, one-chambered or composite, multi-chambered galls on rhizomes, roots, rarely on root collar oblong, up to 10 mm long. Containing a single white larva. R. acetosella: Apion frumentarium

7b Oblong, rotund swelling on roots. Rumex spp.: Apion frumentarium

8a Galls on upper part of roots or root collar, very irregularly shaped, usually variously coalesced into tuberose, ± gnarled complexes, rotund- to oblong-oval, 10–30 mm long with several, irregular, crossing feeding tunnels. R. acetosella: Perapion marchicum

8b Swelling containing one or two chambers. R. acetosella: Apion rubiginosum

8c Irregularly rounded, succulent swellings on upper root part or on root collar, about 15 mm long and 10 mm thick, one- to multi-chambered. R. acetosa: Apion sp.

9a Galls restricted to single plant parts; on leaves, stems, inflorescences or fruits => 16

9b Gall development localised or diffuse, usually on several plant parts => 10

10a Galls caused by smut fungi, their pale- to dark violet spores translucent and dusty later on => 13

10b Galls induced by other causes => 11

= (Regarding malformations caused by animals living on host surface, see lead 29)

11a Causers develop inside galls => 12

11b Mycelium overwintering in rhizome, grows together with above ground plant parts and develops very dense, violet-grey down of branched conidiophores on completely covered leaf undersides, stem of inflorescence and flower parts. Diseased leaves are erect and rigid, leaf blades reduced, pale-green or reddened, slightly thickened, at margin usually distinctly rolled downwards. Inflorescences and flowers reduced, variously disfigured. R. acetosa, acetosella, alpestris, scutatus, thyrsiflorus, rarely crispus: Peronospora rumicis

12a Scattered swellings on basal-, more rarely on stem leaves, up to about 1 mm broad, flat, rotund, red-brown; coalescing on stems, often developing long knobby bulges. Rumex spp.: Physoderma majus

12b Young plants severely stunted, petioles and midribs, basal leaf blade parts, as well as stem primordia, including inserted organs, disfigured, pale green and thickened, spongy. Gall surface ± wrinkled. Later infestation results in development of ± localised galls on leaves and stems. R. acetosa, acetosella, crispus: Ditylenchus dipsaci

13a On several R. acetosa, acetosella, alpestris, thyrsiflorus, etc => 14

13b On R. longifolius, obtusifolius. Conspicuous, usually contiguous pustules, often on leaf margins; galls also on stems and especially on stems of inflorescences and flowers. Infected inflorescences usually completely diseased. Perigone, filaments and ovaries thickened and ± enlarged: Microbotryum warmingii

14a Malformations are inconspicuous swellings => 15

14b Infected plants largely diseased, often crippled, curved, usually sterile. Stem, inflorescence, petioles often distinctly shortened, ± distorted, conspicuously swollen to bloated, with many sori of dark brown-violet spore masses. Leaf blades often hardly unfolded, curved, main veins swollen, distinctly protruding on underside. R. alpinus, maritimus, obtusifolius, palustris: Microbotryum parlatorei

15a Weak swellings on leaves, stems, inflorescence stalks and flowers: Microbotryum kuehneanum

15b Sori inconspicuous, grey-reddish, in pale, thickened leaf blades and -stalks, only rarely in stems and flowers: Microbotryum goeppertianum

16a On inflorescences, flowers or fruits => 33

16b On vegetative parts => 17

17a On leaves => 20

17b On stems and stalks of inflorescences => 18

18a Galls ± spindle-shaped, 10–30 mm long, glabrous, tough-walled with central larval chamber => 19

18b Stem- or inflorescence axis at any point, and occasionally on all sides, weakly thickened; often many feeding tunnels in pith. Larvae whitish. R. acetosa, also on R. conglomeratus, crispus, nemorosus, obtusifolius, patientia, pulcher, etc.: Perapion violaceum

18c Rotund to irregular spindle-shaped swellings mainly of internodes, also on nodes and inflorescence axis, on all sides or sometimes on one side, 5–20 (30) mm long. R. acetosa, etc.: Perapion affine

18d In similar stem galls, e.g., on R. acetosella, hydrolapathum: Apion frumentarium

19a Short to extensive bulging swellings containing pale to dark-violet spore masses 13

19b Stem over variable length stunted on one or all sides and swollen, spongy. Surface ± wrinkled. If infected on one side then ± distorted. Side organs at infestation site clustered and variously galled as well. R. acetosa, crispus, obtusifolius: Ditylenchus dipsaci

20a Extensive malformations, even on large parts of whole leaf blades => 27

20b Gall formation at least of leaf veins, and -stalks or consists of locally restricted, ± rotund or oval galls on leaf blades => 21

21a Galls on leaf blade, often rotund, caused by fungi => 24

21b Spindle-shaped swellings on midrib, rarely on petioles, caused by animals => 22

22a Galls rather constant in size, spindle-shaped, surface glabrous. Containing causers in distinct cavities => 23

22b Midrib over variable length spongy, swollen, malformation ± encroaching onto neighbouring leaf blade areas, often pale-green, with wrinkled surface, Occasionally on petioles. Gall chamber absent. R. acetosa, crispus: Ditylenchus dipsaci

23a Midrib or petiole with spindle-shaped, yellow or red swelling, up to 10 mm long and 5 mm thick, often surrounded by a similar discoloured area. Containing an orange-coloured larva. R. acetosa, acetosella, crispus, ? hydrolapathum, patientia, thyrsoides: Apion frumentarium

23b Swelling in midrib or petiole; containing weevil larva or pupa. R. acetosella: Apion rubens

23c From similar galls on:

a R. acetosa, acetosella, etc.: Perapion curtirostre

b R. conglomeratus, sanguineus, etc.: Apion frumentarium

24a Rotund, more than 3 mm long, usually made conspicuous by red colouration, often hardly gall-like thickened pad caused by the aecia developing mycelium of rust fungi => 25

24b Less than 1 mm long, on the underside of leaf blade usually many flat, colourless, usually 1-celled small warts; also on leaf veins, -stalks. R. acetosa: Synchytrium anomalum

25a Aecidiospores 15‒21 x 12‒18 μm, orange-red when fresh, membrane uniformly with fine warts. Cells of peridium with narrow curved lumen; outer wall reaching far downwards => 26

25b Aecidiospores, diam.16‒26 μm, white. Membrane with fine and also scattered coarse warts. Aecidiosori on leaf underside on up to 10 mm broad, crimson-red, often yellow or pale red bordered spots, wide cup-shaped with white, deflected margin. Cells of peridium in longitudinal section with almost orthogonal lumen; outer wall with only short continuation downwards. Spermogonia whitish to pale-yellow, mainly on leaf upperside. On R. acetosa, etc.: Puccinia phragmitis

26a On R. acetosa, acetosella. Aecia on leaf blades on rotund, 2–5 mm broad, often crimson-red, hardly gall-like thickened spots, often arranged in a circle, mainly on leaf underside. Peridium whitish-yellow, with irregularly lacerate, hardly deflected margin. Sori on main veins and petioles, however, oblong-oval, on often distinctly swollen pads: Uromyces acetosae

26b On R. alpinus. Aecia like those of previous fungus. Spermogonia undescribed: Uromyces acetosae

27a Curling of leaf or –rolls caused by aphids => 31

27b Malformations of leaf blade by other inducers => 28

28a Caused by animals => 29

28b Caused by fungi. Leaves rigidly erect, leaf blades reduced, pale-green, margin ± narrowly rolled inwards, densely covered by grey-violet down of branched conidiophores on underside. R. acetosa, acetosella etc.: Peronospora rumicis

28a Leaf blade variously disfigured or rolled, caused by psyllids => 30

29b Leaf blade usually deflected over tip or laterally loosely rolled, strongly curled and deep green, especially at infestation site. Containing one or more froth-covered nymphs. Rumex spp.: Philaenus spumarius

29c Leaves wrinkled with erinea on underside. R. acetosella: Aculops macrotuberculatus

30a Restricted or extensive downward roll of leaf margin, ± thickened and leather-like. R. acetosella, acetosa, alpinus, scutatus: Trioza rumicis

30b Sorrels of Section Acetosa, Acetosella. Leaves variously disfigured, distorted, reddened, often with deflected margins. R. acetosa, acetosella, scutatus, etc.: Aphalara exilis

30b On Section Rumex, leaf curled downwards, discoloured; with small depressions each containing a froth-covered nymph. R. obtusifolius: Aphalara ulicis

= Furthermore the psyllid Aphalara purpurascens causing enclosed galls on disfigured leaves has been recorded. On R. aquaticus, conglomeratus, crispus, longifolius, obtusifolius

31a Leaf blade curled, also ± rolled or twisted => 32

31b Leaf blades rolled downwards over their length, tube-shaped. Rumex spp.: Aphis rumicis

32a Leaf blade parts strongly curled, irregularly rolled downwards at margin, leaf blade insignificantly thickened and swollen. Aphids black. Rumex spp.: Aphis fabae and/ or Aphis fabae subsp. solanella

= Bulging of leaf blades may primarily be caused by virus

32b Aphid green, leaves twisted, plant stunted, sometimes excessive leafiness. R. acetosella: Brachycaudus helichrysi

33a Galls restricted to flowers or their parts; axial parts only secondarily involved => 39

33b Malformation of ± large parts of inflorescence, flowers included => 34

34a Animal causers => 36

34b Malformations caused by fungi => 35

35a Inflorescence with all parts ± stunted. Buds clustered into dense groups, soon, like also the axial parts, covered with violet-grey down of branched conidiophores. R. acetosa, acetosella and relatives: Peronospora rumicis

35b Usually all flower buds of a plant swollen, variously disfigured. Inner organs soon destroyed by a black-violet, later on slightly dusty spore mass. R. acetosa, alpinus, thyrsiflorus: Microbotryum stygium

36a Caused by psyllids, larvae of beetles or gall midges => 37

36b Internodes stunted, side shoots and flowers ± densely clustered. R. thyrsiflorus, rugosus, etc.: Aphis acetosae

36c Inflorescences stunted; organs clustered like the neighbouring, disfigured stem leaves, bearing many reddish aphids. R. acetosella: Brachycaudus rumexicolens

36d Similar malformation on R acetosella: Unidentified aphid

36e Similar, but often much more extensive malformation. Rumex spp.: Philaenus spumarius

37a Causers live between or in stunted flowers => 38

37b Axis of inflorescence ± shortened and thickened. Flowers clustered, ± stunted and sterile. Containing beetle larvae. R. obtusifolius etc.: Apion sp.

38a Axis shortened; flowers densely clustered, little disfigured; bracts sometimes excessively developed. Between the flowers lives a psyllid. R. acetosella: Unidentified psyllid

38b Axis severely stunted; ± thickened, curved. Flowers clustered in dense balls, disfigured. Larvae reddish. R. acetosa, acetosella, etc.: Jaapiella rubicundula

38c Male flower buds contain midge larvae. R. acetosella: Contarinia rumicina

39a Galls mainly or exclusively on ovaries or fruits => 41

39b Ovaries distorted, gall consists of perigone => 40

40a Flower buds shortly stalked as result of infestation; therefore ± clustered, twice as large as healthy ones; oblong, irregularly bulging, yellowish to reddish. Stamens and ovaries distorted. R. acetosella, pulcher, maritimus: Contarinia rumicis

40b Galls similar. Larvae yellowish-white to orange-coloured. R. acetosa, acetosella: Contarinia acetosellae

41a Galls caused by animals => 42

41b Ovaries transformed into a conspicuous cylindrical or club-shaped gall, up to 3 mm long, 1 mm broad. Containing in nutritive cell 1–3 perennial spores with brown content. R. acetosella: Physoderma acetosellae

42a Malformations in outline ± oval, caused by gall midge larvae => 43

42b Ovaries usually greatly elongated, up to 25 mm long, transformed into a closed tube, or more rarely, with all transitions, into a ± stalked open funnel or cup. Often with 3 lobes at top. Perigone slightly enlarged. Stamens ± aborted. R. alpinus, scutatus: Trioza rumicis

43a Fruit or ovary, including flower, disfigured. Larvae between ovary and ± outwardly bent perigone, sometimes living in fruits. R. acetosella, obtusifolius, scutatus: Contarinia scutati

43b In similar malformations: Contarinia variabilis

mod 22.xi.2019