Dichotomous table for gallers on Diplotaxis
by Hans Roskam
1a On parts above ground => 3
1b On roots or root collar => 2
2a Roots with conspicuous, mostly, spindle-shaped to cylindrical, fleshy swellings. Inside the galls are cells containing spore masses. D. erucoides: Plasmodiophora brassicae
2b Root collar with one to several rotund galls, up to 5 mm long, with a curved larva inside. D. muralis: Ceutorhynchus assimilis
3a On flowers and siliques => 7
3b On stems or leaves => 4
4a Localised or extensive deformations caused by animal gall causers => 5
4b Leaf blade on the underside with flat, rotund cushions. Leaf axial parts or stem with ± expanded, sometimes distorted bulge-like swellings, initially covered with closed dense white sori, at first-glossy, porcelain-like, with mealy dusting after opening. D. muralis, tenuifolia: Albugo candida
5a Deformations caused by aphids => 6
5b About 10–15 mm long, spindle-shaped, partially deep green swellings on the midribs or stems. Containing a single larva. D. muralis, tenuifolia: Ceutorhynchus chalybaeus
6a oung lateral shoots distinctly stunted; occupied by conspicuously reduced and deformed, more densely situated, leaves. D. tenuifolia: Lipaphis rossi
6b Leaf blades folded locally, leaf margins rolled. D. muralis, tenuifolia: Brevicoryne brassicae
7a Malformations caused by gall midges => 9
8b Other causers => 8
8a Greening of flowers. D. muralis, tenuifolia: Brevicoryne brassicae
8b Ovaries in one or several flowers of an inflorescence deformed, narrowed and elongated; anthers shrivelled, corolla stunted; ± greened; calyx partially conspicuously enlarged. On many parts bulge-like white fungal sori occur. D. erucoides, muralis, tenuifolia, virgata: Albugo candida
9a Malformations of flowers or flower parts => 10
9b Swelling of silique => 11
10a Single or several buds per inflorescence distinctly swollen, unopened. Similar galls; calyx and corolla sometimes less swollen. larva usually lighter yellow, jumping. D. muralis, tenuifolia: Contarinia nasturtii
10b Swollen flower buds. White, non-jumping larvae. D. muralis, D. catholica, D. erucoides: Gephyraulus diplotaxis
10c Swollen siliques, inside only one larva. Pupation in gall. Two generations. D. tenuifolia: Asphondylia stefanii
11a Spindle-shaped swelling of silique, often silique bent at right angle. D. tenuifolia: Dasineura napi
11b Siliques swollen, containing a single orange midge larva. D. tenuifolia:
Asphondylia stefanii
11b Siliques turgid, deformed and curved. D. tenuifolia: Dasineura napi