Dichotomous table for gallers on Sinapis

(incl. Coincya)

by Hans Roskam

1a On parts above ground => 5

1b On roots or root collar => 2

2a Galls on roots => 3

2b Whitish, rotund, one-chambered swellings on root collar, up to about 6 mm long, sometimes with several and ± coalescing. Each chamber containing a single white larva. S. alba, arvensis: Ceutorhynchus assimilis

3a Malformations mainly on lateral roots, only exceptionally more than 5 mm long and 3 mm wide => 4

3b Galls of very variable size, conspicuous on main- lateral roots; spindle-shaped to cylindrical, usually more than 10 mm, up to even 20 mm long and about 4–8 mm wide; sometimes encroaching from the main root onto the branchings, also coalesced into larger groups; succulent. Inside are masses of minute spores. “Clubroot”. S. alba, arvensis & subsp. allionii: Plasmodiophora brassicae

4a Roots with small nodular to elongate cylindrical, usually many swellings bearing several lateral roots. S. alba, arvensis: Meloidogyne hapla

4b Outside of roots unchanged; inside with giant cells, bearing poppy seed-sized white to brown cysts. S. alba, arvensis: Heterodera sp.

= Scattered reports of damage by H. schachtii, H. trifolii and H. cruciferae

5a Malformations on inflorescences, flowers or siliques => 16

5b Galls on leaves, axial buds or stems, in the latter case sometimes encroaching onto inflorescences => 6

6a Gall formations ± delimited in expansion, usually only on parts of infected organs => 10

6b Malformations of irregular shape and expansion; usually on various organs => 7

7a On organs of ± fully developed plants => 8

7b Young plants severely stunted and disfigured. Petioles and main venation as well as shoots stunted, pale green, spongy. S. alba, arvensis: Ditylenchus dipsaci

8a The inducers develop on the outside of mostly terminal malformations => 9

8b Stem slightly swollen to large extent. In the increased pith of the ± disfigured, stunted and sometimes distorted plants live several beetle larvae. S. arvensis: Ceutorhynchus napi

9a Axis of the tips of vegetative- or developing flowering shoots ± stunted; the inserted organs clustered, development stunted. Leaf blades curved, curled. Flower buds or flowers variously disfigured. S. alba, arvensis: Brevicoryne brassicae

9b Stem locally stunted, sometimes bent; the inserted leaves clustered; the leaf blade arched, at the infestation site ± curled and discoloured deep green. S. alba, arvensis: Philaenus spumarius

10a Galls on well-developed stems or leaves => 11

10b Terminal, also lateral shoots, and axillary buds severely stunted in longitudinal growth. Leaves clustered, the inner ones developing into rosette- to bud-like galls, especially thickened at base. Containing several whitish to pale yellow, jumping larvae. S. alba, arvensis: Contarinia nasturtii

11a Malformations caused by fungi => 15

11b Malformations caused by animals => 12

12a Causers inside entirely deep green galls => 14

12b Causers develop outside the malformations => 13

13a Leaf blade with small, localised swellings. S. arvensis: Inducer unidentified – ? psyllid

13b Leaf blade ± folded, or variously deflected or bent upwards at margin, usually pale green, sometimes reddish marbled. S. alba, arvensis: Brevicoryne brassicae

= Lipaphis erysimi, which is facultatively cecidogenic on several crucifers, also occurs on Sinapis.

14a Galls flat spindle-shaped, 10–15 mm long; mainly on midrib, midrib or petioles, occasionally on stems. Containing a single larva. S. alba, arvensis: Ceutorhynchus chalybaeus

14b Galls flat rotund-oval, including the finer venation situated in the leaf blade. S. arvensis: Ceutorhynchus leprieuri

15a Leaf blade on underside with rotund bulges, up to 10 mm wide, or young stem parts ± spindle-shaped, often expanded, which are at first glossy, porcelain-like, later rupturing and with mealy dusted sori. S. arvensis, rarely S. alba: Albugo candida s. lat.

15b Leaf blade with weak bladder-like swellings; young stem sometimes with conspicuous, usually one-sided, ± distorted bulge-like swellings, soon covered with a whitish down of branched conidiophores. S. alba & subsp. dissecta, arvensis & subsp. allionii: Hyaloperonospora brassicae

16a Malformations on inflorescences or flowers => 17

16b Siliques usually only insignificantly stunted and disfigured; ± sterile, early (prematurely) maturing; contain several white larvae. S. alba, arvensis: Dasineura napi

17a Malformations caused by fungi => 22

17b Malformations caused by other inducers => 18

18a Galls on single or several flowers of inflorescences that are not additionally conspicuously stunted => 21

18b Axis usually ± stunted with clustered flower buds => 19

19a Malformations not abnormally pubescent => 20

19b Calyx little changed; inner flower parts transformed into ± leaf-like organs or greened; infected parts excessively pubescent. S. arvensis: Unidentified gall mite

20a Flower buds clustered on the stunted, hardly swollen axial parts. Containing several white to pale yellow jumping larvae. S. alba, arvensis: Contarinia nasturtii

20b Flowers largely stunted; at terminal parts of racemes sometimes normally arranged or more clustered; only the sterile remaining ovary is greatly enlarged. S. arvensis: Inducer unidentified – ? aphid

21a Flower buds enlarged, inflated, unopened. Corolla ± stunted. Stamens shortened and thickened. Containing several white, non-jumping larvae. S. alba, arvensis: Gephyraulus raphanistri

21b Galls similar. Larvae whitish to lemon-yellow, jumping. S. alba, arvensis: Contarinia nasturtii

22a Diseased flowers, with exception of stamens, often conspicuously enlarged. At first glossy, porcelain-like, soon bearing mealy dusted sori. Mainly occurring on single flowers; sometimes flower peduncle and midrib of galled inflorescence is also often elongated. S. alba, arvensis & subsp. allionii: Albugo candida

22b In the infected flowers, often inserted on short stalks, only the ovaries are hypertrophied, later on bearing down of branched conidiophores. All other organs ± strongly atrophied. Usually several to many flowers on the ± swollen and distorted axis of inflorescences are similarly galled, also covered with conidiophores. Galls partially contain oospores. S. alba & subsp. dissecta, arvensis & subsp. allionii: Hyaloperonospora brassicae

mod 30.iii.2020