Plant Parasites of Europe

leafminers, galls and fungi

gallers on Linaria

Dichotomous table for gallers on Linaria

(incl. Cymbalaria muralis [= L. cymbalaria], Misopates)

by Hans Roskam

1a On parts above ground => 3

1b On subterranean parts => 2

2a Roots with small, nodular compact swellings. L. vulgaris: Meloidogyne hapla

2b Conspicuous, rotund galls, up to 4 mm long, succulent, one-chambered on root parts close to surface or on subterranean runners; often clustered and/or coalescing. Each chamber containing a single, pale-headed beetle larva. L. genistifolia, loeselii, odora, repens, vulgaris: Rhinusa linariae

= Inquiline in galls of R. linariae; larvae with brown-yellow head: Rhinusa collina

3a Flowers or fruits disfigured => 14

3b Malformation of vegetative parts => 4

4a Malformation of single leaves or of many organs terminally on shoots => 10

4b Galls on axial parts of shoot => 5

5a Causers are inside galls => 6

5b Shoot axis locally ± bulging, with rimmed depressions which contain a single froth-covered nymph. Linaria spp.: Planchonia arabidis

6a Locally defined galls contain causer in chambers or feeding tunnels => 7

6b Mycelium penetrates the whole plant and disfigures the shortened stems which are quill-like over large areas. The black sori, also occurring in leaf bases, are lead-grey translucent before rupturing. L. genistifolia, repens, vulgaris: Melanotaenium cingens

6c Spongy swelling of basal organs. L. arvensis: Ditylenchus dipsaci

7a Distinct rotund or oblong swellings => 8

7b Axis with weak, inconspicuous, spindle-shaped swelling caused by several tunneling larvae. L. genistifolia, repens, vulgaris: Mecinus janthinus

7c Ditto. L. genistifolia, vulgaris: Mecinus heydeni

7d Inconspicuous unilocular swelling at the root collar. L. saxatilis, simplex, supina, thymifolia: Mecinus dorsalis

7e Weak swelling in the lower part of a young shoot; the section above the gall becomes stunted. In the gall several larvae. L. genistifolia subsp. dalmatica: Mecinus peterharrisi

7f On L. purpurea; gall undescribed. Mecinus raphaelis

8a Gall wall fleshy => 9

8b In the oblong, multi-chambered swelling the single chambers have tough, leathery-woody walls. L. vulgaris: ? Aulacidea sp.

9a Up to 8 mm long, one-chambered oblong-cylindrical to pointed barrel-shaped galls develop solitarily or are joined into oblong, multichambered, usually conspicuous tuberculate hunchbacked swellings, up to 30 mm long and 12 mm broad. L. heterophylla, purpurea, simplex, vulgaris: Rhinusa pilosa

= Inquiline in galls of Rhinusa pilosa: Rhinusa collina

9b Multichambered swelling, 20–30 mm long, usually weakly hunchbacked. L. vulgaris, ? genistifolia: Rhinusa thapsicola

9c Oblong, spindle-shaped swelling, 15 x 1.7 mm, usually discoloured violet. L. purpurea, reflexa, repens, supina; Misopates orontium: Mecinus barbarus

9d On similar galls. L. genistifolia incl. subsp. dalmatica, repens, vulgaris; Misopates orontium: Rhinusa neta

= Breeding of Mecinus and Rhinusa species mentioned in leads 7 and 9 is necessary for reliable identification

10a Galls mainly on leaves => 13

10b Malformations involve stem parts => 11

11a Malformation, with involvement of axial parts of expanded shoot parts => 12

11b The distinctly shortened and broadened, thickened terminal leaves are transformed into an oblong, often bud-like tuft containing ivory-white midge larvae. L. genistifolia, purpurea, vulgaris: Diodaulus linariae

12a Complete plant disfigured, excessive branching, young flowers variously greened. L. vulgaris: Cause unknown – ? gall mite

12b Shoot axis stunted, sometimes one-sided ± bent, inserted leaves deflected, locally deep green, ± accumulated, nest-like. Linaria spp.: Philaenus spumarius

12c Leaves curled. Cymbalaria muralis: Aphis gossypii

13a On basal leaves, usually on underside, many warts, less than 1 mm long, multi-cellular, yellow translucent, also on basal stem parts; sometimes joined into crusts or ridges. L. vulgaris: Synchytrium aureum

13b Many leaves on shoot tip ± stunted, wrinkled, the curly margin deflected or ± rolled; leaf blade wrinkled, irregularly curved and twisted, occasionally excessive budding or branching. L. vulgaris: Unidentified gall mite

14a Malformation mainly of ovary or capsule => 16

14b Malformation mainly of several flower parts => 15

15a Flower buds swollen, all parts ± disfigured and unfolding buds greened. Larvae ivory-white. L. genistifolia, purpurea, vulgaris: Diodaulus linariae

15b Gall-like malformation on flowers and inflorescences. L. arvensis: Unidentified thrips

15c Flowers are swollen; with a weevil larva or pupa inside. L. genistifolia: Rhinusa florum

16a Ovary swollen, often already in unopened, swollen flower, or disfigured after flowering, compact, often with irregular proliferations; caused by whitish beetle larvae. L. genistifolia incl. subsp. dalmatica, repens, vulgaris; Misopates orontium: Rhinusa neta

16b On L. genistifolia incl. subsp. dalmatica, repens, vulgaris live in similar, less conspicuous malformations the brown- to dark-brown headed larvae of Rhinusa antirrhini

16c On L. vulgaris, in similar galls lives also Rhinusa tetra and/or Rhinusa collina

16d Capsule galls, two or more times as large as healthy capsules. Containing a single larva. L. vulgaris, ? genistifolia: Rhinusa thapsicola

16e Similar malformations caused by a yellow-green caterpillar with angular transverse stripes on body segments. L. vulgaris: Eupithecia linariata

Last modified 30.iii.2020