Plant Parasites of Europe

leafminers, galls and fungi

gallers on Raphanus

Dichotomous table for gallers on Raphanus

by Hans Roskam

1a On parts above ground => 5

1b On roots or on root collar => 2

2a Galls more than 5 mm long => 4

2b Galls smaller => 3

3a Roots with nodular swellings, which bear several lateral roots. R. raphanistrum, sativus: Meloidogyne hapla

3b Root not disfigured from the outside, with giant cells inside. Cysts up to 0.8 mm long. Raphanus spp.: Heterodera schachtii and/or Heterodera cruciferae

4a About 6–10 mm long, rotund galls with central larval chamber; mainly on upper part of root or on root collar; often several and mutually ± coalescing. R. raphanistrum, sativus: Ceutorhynchus assimilis

4b Conspicuous, spindle-shaped, succulent swellings on roots, of variable size, depending on the infected organ; larval chambers absent. “Clubroot”. R. raphanistrum & subsp. rostratus, sativus: Plasmodiophora brassicae

= Usually occurring on the root collar, nodular proliferations of the polyphagous bacterium Agrobacterium tumefaciens have been recorded

4c Smaller galls of variable shape on the root head of R. raphanistrum, sativus & subsp. niger + radicula are sometimes caused by the oospore bearing mycelium of Albugo candida

5a On inflorescences, flowers or fruits => 13

5b On vegetative parts => 6

6a On stems, petioles or axial parts, exceptionally encroaching into the leaf blade => 10

6b Malformations mainly on leaf blades, with or without involvement of venation => 7

7a Galls caused by fungi, or inducers live inside galls => 9

7b Inducers live in folds or curls on the surface of disfigured organs => 8

8a Main venation stunted to varied extent, thickened, usually distinctly discoloured. The neighbouring leaf blade parts folded upwards, especially up to the centre of the gall strongly undulately curled. Containing several whitish- to lemon-yellow, jumping midge larvae. R. caudatus, raphanistrum, sativus & subsp. niger: Contarinia nasturtii

8b Leaf blade variously bulging or deflected at margin, irregularly curled and ± discoloured. Infestation site sometimes reddish marbled. Upper- and underside of the malformations bearing colonies of mealy powdered aphids. R. raphanistrum, sativus: Brevicoryne brassicae

9a Rotund, flat lenticular galls, up to 5 mm broad, succulent, protruding on both sides, usually deep green. Often enclosing a larger vein of the leaf blade. Often several to many galls per leaf. Contain a beetle larva in a central chamber. R. raphanistrum, sativus: Ceutorhynchus leprieuri

9b Leaf blade often with only weak, locally upward swellings, 5–10 mm broad, pale green, on underside in often ring-shaped arrangement white, at first glossy, porcelain-like, later on rupturing and with mealy dusting of sori. Sometimes also similar, more elongated bulges on axial parts and exceptionally even on root caps. R. raphanistrum, sativus & subsp. niger + radicula: Albugo candida

9c Leaf with small hard gregarious pustules, less than 0.5 mm across, solid; containing fungi. Raphanus spp.: Synchytrium aureum

10a Localised galls on stems or axial parts => 12

10b Expanded galls on axis of shoot and leaves => 11

11a Young plants severely stunted. Petioles, stems, as well as main venation severely stunted, spongy, swollen, ± pale green, ± wrinkled. Galls sometimes variously encroaching into leaf blade. R. raphanistrum: Ditylenchus dipsaci

11b Stem swollen over extensive areas, ± stunted and curved, the inserted organs ± clustered. Galls on the more swollen parts often erupting later on. Pith containing many beetle larvae. R. raphanistrum: Ceutorhynchus napi

12a Spindle-shaped gall, up to about 15 mm long, also deep green inside, remaining green in yellowing leaves. Usually on petiole or midrib, occasionally on stem. Containing a single beetle larva. Raphanus spp.: Ceutorhynchus chalybaeus

12b Petiole and lower part of midrib swollen and ± deflected, the stem leaves are occasionally stunted, inside often dark translucent. Containing a single or several beetle larvae. R. raphanistrum, sativus: Ceutorhynchus pallidactylus

13a Galls mainly on flowers or fruits => 18

13b Gall formation also, or mainly, on axial parts => 14

14a Malformations caused by fungi => 17

14b Malformations caused by other agent => 15

15a Malformations bearing a few to many aphids => 16

15b Stalks of inflorescence tips severely stunted, not thickened, with densely clustered, unopened, ± swollen flower buds. Whitish to lemon-yellow larvae living within and between. R. caudatus, raphanistrum, sativus & subsp. niger: Contarinia nasturtii

16a Stalks of inflorescences often with small colonies of mealy powdered aphids. Axial parts variously shortened, sometimes slightly thickened and curved. Flowers clustered, sometimes incompletely unfolding their partially reduced and disfigured, greened and leafy organs. Usually all flowers soon wither on strongly infected, hardly shortened axial parts. R. sativus: cf. Brevicoryne brassicae

16b Axial parts strongly shortened. Flower buds, or flowers united into dense clusters, their parts ± greened; ovaries or young fruits disfigured and ± atrophied. R. raphanistrum, sativus: Lipaphis erysimi

17a Young inflorescence stalks to large extent thickened on all sides, sometimes slightly bent, soon covered with a down of branched conidiophores. Infestation occasionally encroaching into flower peduncles and flowers; inhibiting the development of all diseased flower parts. R. raphanistrum, sativus: Hyaloperonospora brassicae

17b Axis usually with one-sided white bulges, sometimes over 10 mm long, and curving, glossy, porcelain-like, after rupturing with dusting with conidia arranged in chains. Occasionally on flower peduncles and usually independently from these in flowers. R. raphanistrum, sativus & subsp. niger + radicula: Albugo candida

18a On flowers => 19

18b On fruits. Siliques variously locally ± swollen, discoloured, disfigured, ± sterile, maturing early. One or more white midge larvae inside. R. raphanistrum, sativus, also R. caudatus, raphanistrum & subsp. landra, sativus: Dasineura napi

19a Malformations caused by midge larvae => 19

19b Flowers severely disfigured. Calyx swollen, corolla greened. Stamens reduced. Ovaries strongly enlarged, and like the perianth parts, bearing white sori with conidia. R. raphanistrum, sativus & subsp. niger + radicula: Albugo candida

20a Flowers unopened, especially strongly swollen at base. Calyx enlarged, corolla and stamens shortened, anthers ± swollen. Stigma reduced, ovaries disfigured and thickened. Containing several, mature white, non-jumping larvae. R. raphanistrum, sativus: Gephyraulus raphanistri

20b Flowers similarly disfigured. Galls often smaller than previous ones, at base slightly less swollen. Larvae whitish- to lemon-yellow, jumping. R. caudatus, raphanistrum, sativus & subsp. niger: Contarinia nasturtii

Last modified 11.iv.2020