Dichotomous table for gallers on Capsella

by Hans Roskam

1a On parts above ground => 5

1b On root collar or on roots => 2

2a On roots => 3

2b Root collar with rotund, 5–7 mm long, succulent, one-chambered gall. Containing a single larva. C. bursa-pastoris: Ceutorhynchus assimilis

3a Outside of roots hardly changed or with small, ± nodular swellings => 4

3b Conspicuous, succulent, spindle-shaped to expanded barrel-shaped, compact swellings of variable size on main- and side roots. C. bursa-pastoris: Plasmodiophora brassicae

4a Side roots with small, nodule- or spindle-shaped swellings. C. bursa-pastoris: Meloidogyne hapla

4b Outside of roots not noticeably changed; giant cells inside; temporarily with at first white, later on partially browned lemon-shaped cysts, about poppy seed size. C. bursa-pastoris: Heterodera cruciferae and/or H. schachtii

5a Galls on various parts caused by fungi sporulating at surface => 18

5b Malformations caused by animals => 6

6a Malformation of ± extensive parts caused by aphids or spittlebugs => 10

6b Galls caused by other parasites => 7

7a On stems or leaf midrib => 8

7b Phyllanthy, flowers greened or leafy; infestation encroaching also on vegetative parts. Stalk of inflorescence stunted; leaves stunted, ± rolled inwards and twisted. All diseased parts densely pubescent, hairs branched and 3–4 times longer than the normal ones. C. bursa-pastoris: Aceria drabae

7c Swollen flower bud, preventing development of fruits; each attacked flower bud with 1‒3 larvae; pupation in soil, more generations. Capsella bursa-pastoris: Gephyraulus capsellae

7d Young siliques slightly disfigured. Contain several (1) 3 (6) white larvae. C. bursa-pastoris: Dasineura napi

= The gall midge Contarinia nasturtii has been reported from on C. bursa-pastoris.

8a Inducers inside the galls => 9

8b Stem spindle-shaped to irregularly bulging; rind with rotund-oval, sometimes rimmed depressions containing a froth-covered nymph of the polyphagous inducer. C. bursa-pastoris: Planchonia arabidis

9a Spindle-shaped glabrous galls, 10–40 mm long swellings or oblong-oval, flattened, compact, at first succulent, also deep green inside, on petioles and leaf veins. Containing a single, curved larva. C. bursa-pastoris: Ceutorhynchus chalybaeus

9b Stems of young plants severely stunted and spongy thickened; leaves stunted; especially basal parts swollen; infestation of older plants results in ± expanded, local, sometimes strongly curved swellings on stems and leaves. Gall always pale green, brittle, ± wrinkled at surface. C. bursa-pastoris: Ditylenchus dipsaci

10a Malformations caused by aphids => 11

10b Inflorescence stunted, flowers of sometimes one-sided curved midrib clustered, ± stunted. With a froth-covered nymph. C. bursa-pastoris: Philaenus spumarius

11a Malformations of various shape and expansion; atypical for this causer. Aphid green => 12

11b Shoot tips ± stunted; leaves, and flowers clustered; leaf blades deflected, slightly curled. Flowers disfigured, ± greened. Aphids black. C. bursa-pastoris: Aphis fabae and/or Aphis fabae subsp. evonymi

12a Malformations usually restricted to some parts terminally on shoots or on leaves => 13

12b Infected young plants with severely stunted shoots, leaves rolled inwards and curled; plant often completely disfigured. Axis of inflorescence and flower peduncles shortened, ± curved. Flower parts stunted and disfigured, ± discoloured, also greened or violet; siliques disfigured, bent. Aphid 1.5–2 mm, grey-green to grey-yellowish, antennae half the body length, siphunculi yellow, cauda oblong, pale greenish. C. bursa-pastoris: Lipaphis erysimi

13a Aphid not covered with wax powder => 14

13b Aphid 2–2.5 mm long, yellowish–green, with two longitudinal rows of small cross stripes, densely white powdered C. bursa-pastoris: Brevicoryne brassicae

14a Aphid yellow to green => 15

14b Aphid dark green, up to 2 mm long, antennae half the body length. Siphunculi black, cauda oblong, pale green to yellowish-white. C. bursa-pastoris: Aphis gossypii

15a Aphid yellow to greenish-yellow or pale green => 16

15b Aphid green; siphunculi black, cauda oblong, brown. C. bursa-pastoris: Aphis gossypii subsp. capsellae

16a Cauda of aphid oblong => 17

16b Cauda short, broad and rounded. Aphid hardly 2 mm long, greenish to yellowish; mainly on basal leaves on slightly rolled leaves. C. bursa-pastoris: Brachycaudus cardui subsp. lateralis

17a Antennae of the about 2–3 mm long aphid longer than the mainly yellowish-green to straw-coloured body, darker green at the insertion of siphunculi; these yellow to orange-coloured, with blackish tip. Leaves weakly rolled downwards or curved and slightly arched. C. bursa-pastoris: Aulacorthum solani

17b Antennae of the about 1–1.5 mm long, yellowish to pale green aphid surpassing the anterior half of the body, siphunculi and cauda same colour as body. Inflorescence stunted, bearing more densely clustered flowers. Leaves ± downwards deflected, sometimes bulging. C. bursa-pastoris: Aphis nasturtii

18a Bulge-like, at first closed, glossy, porcelain-like, after rupturing mealy dusting sori of variable size on all green parts. Often causing diverse swellings and distortions. Infestation of flowers results in often conspicuous malformations of ovaries. C. bursa-pastoris: Albugo candida

18b Stem and also axis of inflorescence usually with expanded, conspicuous, often distorted swellings, soon covered with a down of branched conidiophores. Flowers of diseased inflorescences severely stunted. Leaves of axillary shoots if infected early, ± spoon-like arched, thickened, brittle, pale green; with a dense down of conidiophores on underside. C. bursa-pastoris: Hyaloperonospora parasitica

18c Leaf with hard gregarious pustules, less than 0.5 mm across; contain fungi. C. bursa-pastoris: Synchytrium aureum

mod 18.iii.2020