Dichotomous table for gallers on Lathyrus

by Hans Roskam

1a On shoot parts => 4

1b On roots => 2

2a Conspicuous galls => 3

2b Outside of roots not conspicuously changed, giant cells developing inside; at surface temporarily with poppy seed sized egg capsules. Lathyrus spp.: Heterodera sp.

3a Nodular swelling in root body. L. odoratus: Meloidogyne sp.

3b Slender oval to cylindrical galls which grow on roots of very different thickness, apically often branched or hand- to coral-shaped, subdivided, on many hosts, up to 8 mm long and 1.5 mm broad, sometimes united into larger complexes. Lathyrus spp.: Rhizobium leguminosarum

4a On inflorescences, flowers or fruits => 36

4b On vegetative parts => 5

5a Galling confined to leaf blades or buds => 16

5b Galling on other vegetative parts including malformations of terminal shoot => 6

6a Malformations mainly or exclusively confined on stem or axial parts => 13

6b Extensive malformation of complete shoot systems => 7

7a Usually expanded malformations of shoot tips => 9

7b Galls on basal parts => 8

8a At stem base are several close shoots, severely stunted, succulent, thickened, ± curved and bearing minute, crippled small leaves. L. odoratus: Rhodococcus fascians

8b Stem bases of young plants stunted in development, severely stunted and over about 40 mm long, spongy, swollen; petioles and basal veins of infected leaves similarly swollen. L. odoratus: Ditylenchus dipsaci

9a Malformations by animal causers => 11

9b Systemic diseased shoot tips show a stunting of internodes and bear slightly clustered, stunted, pale, at margin ± deflected and relatively thickened leaves, which on their underside, as on the young shoot axis, are covered with a whitish-grey down of conidia => 10

10a On L. palustris, heterophyllus, sylvestris: Peronospora lathyri-palustris

10b On different Lathyrus species:

a On L. linifolius: Peronospora orobi

b On L. niger: Peronospora senneniana

c On L. pratensis, nissolia: Peronospora trifoliorum

= These cecidogenic fungi develop systemic infections, and may induce different responses in different host plants. Any additional assignations of Peronospora forms on different Lathyrus species require further study; additional micro-species have also been described from southern areas

= Furthermore Peronospora viciae, frequent on several Lathyrus species, also on Pisum and Vicia, causes proliferating leaves and buds forming a rosette

11a The margins of ± stunted leaflets of many leaves are rolled => 12

11b Few to several leaves are usually at the one-sided bent axis ± deflected, locally deep green and are nest-like converging. Lathyrus spp.: Philaenus spumarius

12a Leaflets mainly of the terminal leaves with narrow, hardly discoloured upward rolled margins. L. pratensis, sylvestris: Aculops lathyri

12b The stunted leaflets usually of all leaves on the strongly necrotic plant are loosely rolled upwards, yellow-green, not thickened. L. pratensis: Odontothrips loti and/ or O. phaleratus

= Stunting of various parts are occasionally caused by the black-brown “pea thrips” Kakothrips robustus

13a Shoot axis with localised spindle-shaped or semi-globular galls => 14

13b Wart-shaped, green galls on stems, usually coalescing into broadened crusts. L. niger: Synchytrium viride

14a Bulges caused by fungi with distinct fruiting bodies on the outsides => 15

14b Stem with swelling on all sides, spindle-shaped, up to 10 mm long with central chamber. L. annuus, cicera, etc.: Holotrichapion gracilicolle

= The larva of Cyanapion columbinum lives in elongated one-sided stem galls and pod-like galls on leaves of L. heterophyllus

15a More or less semiglobular or oval galls, 3 x 10 mm long, many occurring on upper stem parts, inflorescence stalk as well as in petioles. L. linifolius, pratensis: Physoderma lathyri

15b The aecia bearing mycelium may develop facultatively spindle-shaped, slightly swollen sori on responsive stem parts or petioles. Aecia small, depressed, with yellowish, broadly deflected, with lacerate margins usually in loose groups on leaf spots. Lathyrus spp.: Uromyces viciae-fabae

16a Galls induced on single leaves or their parts => 19

16b Several leaves involved in the development of a ± bud-like or onion-like swollen single gall => 17

17a Malformations of shoot tip => 18

17b Rough swelling of bud in leaf axil. Containing a single larva. L. pratensis: Cyanapion alcyoneum

18a The stipules enclose a mass of disfigured leaves or inflorescence buds, resulting in a ± globular gall at the shoot tip; internodes of terminal shoot partly shortened. Larvae gregarious, yellowish-white. L. pratensis: Contarinia jaapi

18b Inflorescence transformed into a rotund structure bearing many, ± largely stunted buds; these completely reduced and ± greened. Gregarious white larvae. L. pratensis, ? clymenum: Dasineura pratensis

18c Two terminal stipules slightly swollen at base and ± discoloured and enveloping a mass of dying tissues. Terminal shoot stops further growth and dies. Usually complete plant ± dwindling and non-flowering. Larvae gregarious, from white to pale red. L. pratensis, ? sylvestris, ? tuberosus, ? vernus: Dasineura lathyricola

= Yellow larvae of Dasineura lathyrina develop as inquilines in galls caused by D. lathyricola

= Several unidentified gall midges have been recorded on tips of side- and terminal ± onion-like swollen shoots. Leaflets ± strongly enlarged, fleshy thickened, brittle, ± leather-like folded upwards. Larva whitish or also orange-coloured. Because of the different colour of larvae several midge species are probably involved.

19a Malformation of leaves and buds caused by a false mildew, forming a rosette and causing further distortions => 10

19b Malformations of leaf blade or petiole => 20

20a Malformations of leaf blade => 21

20b Petiole with weak spindle-shaped swelling. L. vernus: Apion sp.

21a Marginal roll or pod-like fold of leaf => 23

21b Curling of leaf or locally defined galls on unfolded leaf blade => 22

22a More or less rotund to oval galls on leaf blade. L. linifolius: Physoderma lathyri

= Enations on leaves of Lathyrus species are often caused by viruses.

22b Leaf curls associated with other malformations. Unidentified aphid

23a Loose to compact, even cartilaginous marginal rolls or also folds caused by midge larvae => 24

23b Leaf margin over variable length irregularly rolled, occasionally up to midrib. The gall wall is variously thickened and appears to be ± hard, sometimes brittle and yellowish spotted. L. sylvestris, also L. cicera, heterophyllus, latifolius, pratensis, tuberosus: Cyanapion columbinum

23c Leaflets mainly of the terminal leaves with narrow, hardly discoloured upward rolled margins. L. pratensis, sylvestris: Aculops lathyri

24a Galls on different Lathyrus species => 28

24b Galls on L. pratensis (records on different Lathyrus species are marked with ‘?’ need verification) => 25

25a Leaflets or stipules with rolled margins => 26

25b Leaflet or stipule swollen and folded over midrib, forming a soft discoloured pod ± mussle-shaped. L. pratensis: Dasineura lathyri

26a Marginal roll usually on one side, not involving the whole margin => 27

26b Marginal roll often enlarged, violet discoloured, rolled upwards over midrib on both sides. Originally described as looking like a cowry shell. Reddish larvae. On L. ? pratensis, sylvestris: Anabremia bellevoyei

27a The not thickened, soft and hardly discoloured leaflets are ± tightly rolled upwards. Larvae yellowish white at first, later pale red: Jaapiella volvens

27b Marginal roll hardly thickened and not discoloured, one or both margins rolled inwards. Usually in the topmost parts of the plant ± dwindling and non-flowering. Larvae gregarious, from white to pale red. L. pratensis, ? sylvestris, ? tuberosus, ? vernus: Dasineura lathyricola

28a Galls on different species of Lathyrus (not on L. linifolius) => 29

28b On L. linifolius, ? sylvestris. Tube-shaped to cylindrical, not thickened and discoloured, sometimes ± reddened roll containing white to pink coloured larvae: Lathyromyza schlechtendali

29a Galls on L. vernus => 30

29b Galls on L. palustris and L. sylvestris group, including L. heterophyllus, latifolius, odoratus, tuberosus => 31

30a Cartilaginous roll on leaflets and stipules. Larvae yellowish. Macrolabis orobi

30b On leaflets and also stipules the roll, often of only a part of the margin and usually apically situated, does not reach the basal part of median vein: Unidentified gall midge

31a The upwardly bent parts are fleshy to cartilaginously thickened => 33

31b Leaflets or also stipules weakly enlarged, softly rolled upwards => 32

32a The not thickened, soft and hardly discoloured leaflets rolled upwards on L. sylvestris. Larvae whitish: Unidentified gall midge

32b On leaflets and also stipules the roll, often of only a part of the margin and usually apically situated, does not reach the basal part of median vein, contain whitish larvae. L. tuberosus: Unidentified gall midge

32c Roll on leaflets, often of only a part of the margin, does not reach the basal part of median vein. Containing pale orange larvae. L. palustris, vernus: Macrolabis orobi

33a Galls on L. pannonicus and L. tuberosus => 34

33b Galls on L. heterophyllus and L. sylvestris => 35

34a Tube-shaped, strongly enlarged, especially at base, pale green rolling together of ± shortened appearing leaflets. Containing white larvae. L. pannonicus, tuberosus: Various unidentified gall midges

34b More or less unexpanded leaflets are folded upwards. Gall wall strongly thickened, cartilaginous brittle, pale green, sometimes margined by narrow normal leaf blade parts. Containing several larvae. Unidentified gall midge

35a Leaflets or stipules often enlarged, violet discoloured, rolled upwards over midrib on both sides. Reddish larvae. L. sylvestris, ? pratensis: Anabremia bellevoyei

35b Similar gall with fleshy leaf rolls. Reddish larvae, pupation in galls. L. heterophyllus, sylvestris: Geocrypta heterophylli

36a On fruits => 43

36b On inflorescences or flower buds => 37

37a Galls on single flower buds => 39

37b Malformation of inflorescence => 38

38a Inflorescence transformed into a rotund structure bearing many, ± largely stunted buds; these completely reduced and ± greened. Larvae white. L. pratensis, ? clymenum: Dasineura pratensis

38b Already the young inflorescence is severely stunted. Several larvae between flowers. L. tuberosus: Unidentified gall midge

= From L. tuberosus malformations have been assigned to a Contarinia sp.

39a Flower buds swollen, unopened, on several Lathyrus species, but not on those mentioned in lead 39b. Various unidentified gall midges

= Similar galls occur on L. niger with yellow, jumping larvae, as well as on L. vernus with such jumping but cream-coloured larva

39b Flower buds swollen, unopened on L. linifolius, pratensis, tuberosus, odoratus, sylvestris => 40

40a Galls on L. odoratus, sylvestris, tuberosus => 42

40b Galls on L. pratensis and linifolius => 41

41a Flower buds swollen, unopened. Larvae white to lemon-yellow, jumping. L. pratensis: Contarinia lathyri

41b On L. linifolius. Flower buds slightly swollen, unopened. Containing a single white to pink-coloured or reddish larva. Also on L.? sylvestris, ? pratensis,? tuberosus, ? odoratus: Lathyromyza florum

41c Same host, flower galls with yellowish-white, jumping larvae. Unidentified gall midge

42a lower buds slightly swollen, unopened. Larvae vitreous to milk-white, or reddish (after description) non-jumping. L. sylvestris: Dasineura silvestris

42b Similar galls contain a single white to pink-coloured or reddish larva. On L. linifolius, also on L. ? sylvestris,? pratensis, ? tuberosus, ? odoratus: Lathyromyza florum

42c Similar galls contain red, non-jumping larvae. L. sylvestris: Dasineura fairmairei

43a Malformations on fruits caused by insect larvae => 44

43b Malformations on fruits caused by fungi. Fruits by early infestation stunted in further development, only occasionally slightly disfigured. Later on with dusting of dirty brown-violet spores; mycelium destroys only in case of early, externally usually indistinct infestation of all seeds of a pod. Lathyrus (Orobus) species: Thecaphora lathyri

44a Malformations caused by gall midge larvae => 45

44b Beetle larvae feed within the pod on the developing seeds; this may cause some galling of the pods. L. linifolius, pratensis, sylvestris, vernus: Tychius quinquepunctatus

45a Pod bulging. swollen, discoloured. Malformations without fungus inside. Many white to lemon-yellow larvae inside, able to jump. L. sylvester, tuberosus: Contarinia silvestris

45b Local, oval or ± spindle-shaped swellings, inside covered with a dense mycelium. Containing a yellow to orange-yellow midge larva: Asphondylia lathyri

mod 18.xi.2019