Plant Parasites of Europe

leafminers, galls and fungi

gallers on Thlaspi

Dichotomous table for gallers on Thlaspi

by Hans Roskam

1a On parts above ground => 4

1b On root collar or on roots => 2

2a On roots => 3

2b Rotund swellings on root collar, up to 6 mm long one-chambered. Containing a single larva. T. arvense, Noccaea perfoliata: Ceutorhynchus assimilis

2c Rotund root collar galls, 3–5 mm long. Noccaea perfoliata: Ceutorhynchus carinatus

3a Conspicuous, spindle-shaped or cylindrical thick-succulent compact galls, often more than 10 mm long, on main- and side roots, often in smaller sizes on secondary roots. “Clubroot”. Thlaspi spp.: Plasmodiophora brassicae

3b Roots often with many slender, 2–4 mm long cylindrical swellings, provided with several lateral roots. T. arvense, Noccaea brachypetala: Meloidogyne hapla

= Cyst eelworms, both Heterodera cruciferae and H. schachtii have been reported from T. arvense

4a Malformations of indefinite shape extending over several organs or localised to extensive malformations caused by fungi fruiting at surface, sori of which usually occur simultaneously on several organs => 8

4b Locally definite galls of rather similar shape on single organs => 5

5a On inflorescences, flowers or fruits => 17

5b On stems or leaves => 6

6a Galls conspicuous, spindle-shaped or globular => 7

6b Galls wart-shaped, less than 1 mm across, usually many on the underside of basal leaves. Sometimes ± coalesced crust-like; also on petioles and basal parts of young stems. T. rotundifolium: Synchytrium infestans

7a Galls ± globular to acuminated, spindle-shaped, about 5–6 mm long. Containing a single larva. Noccaea perfoliata: Ceutorhynchus carinatus

7b Spindle-shaped glabrous galls, about 20–25 (35) mm long, usually on all sides of stems, sometimes almost node-like, on petioles or midrib ± flattened; especially on leaves also deep green inside; partially with rather long tunneled channels. Containing a single larva. T. arvense, Noccaea brachypetala, perfoliata: Ceutorhynchus chalybaeus

8a On the malformations develop white or brown fruiting bodies of fungi => 14

8b Malformations caused by animals => 9

9a The animals develop outside on the galls, partially distinctly visible, partially hidden by the malformation => 10

9b Young plants largely stunted. Hypocotyls, petiole, and leaf blade base shortened, pale green, spongy. Neighbouring shoots severely stunted and thickened. Later infected stems are swollen over different lengths on one- or all sides, shortened, occasionally bent. Galls at surface undulately wrinkled, ± necrotic, with many eelworms inside. Thlaspi spp.: Ditylenchus dipsaci

10a Malformations caused by aphids or spittlebugs => 12

10b Malformations caused by larvae of gall midges => 11

11a Leaves terminally or laterally on stunted shoots, also in axillary buds ± tuft-like clustered, stunted, thickened at base and discoloured. Primordia of inflorescence are included in the gall, or display densely clustered, severely disfigured buds. Between the organs develop whitish or yellowish-white, jumping larvae. T. arvense: Contarinia nasturtii

11b Shoot tip disfigured. T. montanum: Unidentified gall midge

12a Malformations caused by aphids => 13

12b Young stems stunted and bent over a few internodes. Inserted leaves stunted, ± nest-like converging, undulately curled, locally dark green. T. arvense, Noccaea brachypetala: Philaenus spumarius

13a Tips of vegetative or generative shoots stunted; organs clustered, severely stunted. Aphid 1.5–2 mm long, grey-green to grey-yellow, siphunculi yellow, twice as long as the oblong yellow-green cauda. T. arvense: Lipaphis erysimi

13b Similar malformations, mainly restricted to the tips of shoots or inflorescences on severely disfigured leaves and flower buds, and on fruits and younger parts. Aphid 2–2.5 mm long, yellow-green, with 2 longitudinal rows of small black cross stripes; densely grey powdered; siphunculi short, swollen, brownish-black, about as long as the oblong, dark-green cauda. T. arvense: Brevicoryne brassicae

14a Sori white; infestation very variable, often without distinct malformations => 15

14b Mycelium disfigures the infected shoots completely or in the terminal parts, which bear smaller, thickened, paler leaves and which usually remain sterile. Exceptionally developing flowers are largely disfigured and ± greened. On expanded parts mainly of the leaf undersides develop many punctiform sori with rust- to dark-brown telia. T. alliaceum, arvense, “bulbosum”; Noccaea spp.: Puccinia thlaspeos

15a The sori protruding from the malformations consist of branched conidiophores => 16

15b Sori consist of dense pads, at first closed, glossy, porcelain-like, later on rupturing and with mealy dusting, usually with several, which are rotund on leaf blade underside, ± oblong oval to spindle-shaped and occasionally bent on leaf veins, – stalks and stem parts. T. arvense; Noccaea caerulescens, perfoliata: Albugo candida

16a Infected stem parts pale green, hypertrophied and ± distorted; sometimes slightly swollen during the development of infected leaves. On infected axial parts inserted organs, especially flower buds, severely stunted; diseased siliques usually crippled, occasionally enlarged and swollen. T. arvense: Hyaloperonospora thlaspeos-arvensis

16b On Noccaea brachypetala, caerulescens, causing similar damage: Peronospora thlaspeos-alpestris

16c Similar malformations on Noccaea perfoliata: Hyaloperonospora thlaspeos-perfoliati

17a Galls on single or several flowers or fruits => 18

17b Internodes of inflorescence distinctly shortened. Buds, flowers or young siliques clustered. Flowers partially ± greened. T. arvense: Thrips tabaci

18a Malformations usually inconspicuous, without involvement of other organs, on older ovaries or fruits => 20

18b Flower galls => 19

19a Already largely developed, single or sometimes clustered flower buds strongly swollen, almost globular. Larvae inside the organs or also between densely clustered flower buds; white to pale yellow, jumping. T. arvense; Noccaea brachypetala, caerulescens: Contarinia nasturtii

19b Calyx of opened flowers strongly hypertrophied. Corolla and the broadened stamens ± greened. Ovary severely disfigured, narrowed and elongate. Locally oblong-oval white sori on the diseased organs. T. arvense; Noccaea caerulescens, perfoliata: Albugo candida

20a In largely developed shoots, not or only slightly swollen, develop ivory white to lemon yellow coloured, jumping midge larvae. T. arvense: Contarinia thlaspeos

20b In the seed primordia of hardly disfigured fruits develop yellow-brown to grey-violet spore masses. Noccaea brachypetala, caerulescens, crantzii: Thecaphora thlaspeos

Last modified 1.v.2020