Plant Parasites of Europe

leafminers, galls and fungi

gallers on Armoracia

Dichotomous table for gallers on Armoracia

by Hans Roskam

1a On parts above ground => 4

1b On roots and root collar => 2

2a On root collar => 3

2b Side roots with usually 4–6 mm long, slender, spindle-shaped succulent swellings. Inside the galls cells contain masses of minute spores. Plasmodiophora brassicae

3a Rotund, up to 8 mm long one-chambered galls with a glabrous surface, contain a curved larva. Ceutorhynchus assimilis

3b Proliferations of conspicuous bulging, at surface ± subdivided, up to almost fist size galls, ± one-sided attached to the plant part. Agrobacterium tumefaciens

4a On flowers => 9

4b On stems or leaves => 5

5a Malformations caused by animals => 6

5b eaves on the underside with dense, rotund pads, sometimes in large numbers, rotund on the leaf blades, on the veins bulging, at first glossy, porcelain-like, later opening with mealy dusting of white sori. Albugo candida

5c Leaves somewhat disfigured with pale spots on the upperside, that correspond with a fungal bloom on the underside, consisting of erect, apical strongly branched conidiophores. Hyaloperonospora cochleariae

6a Galls predominate on petioles, leaf veins or on stems => 8

6b Malformations on expanded plant parts or on leaves => 7

7a Basal leaves of young plants loosely deflected over their length, ± curled. Many black aphids on underside. Inducer unidentified – ? aphid

7b Stems of younger main- or side shoots stunted, sometimes curved, leaves deflected, curled, their margins rolled inwards. Inflorescences stunted, flowers densely clustered ball-like. Contain a froth-covered nymph. Philaenus spumarius

8a Galls spindle-shaped, on leaves mainly on underside, 15–25 mm long, glabrous, also green inside, on midribs, petioles, more rarely on rather young stems. Containing a single larva. Ceutorhynchus chalybaeus

8b Spongy, at surface undulate-wrinkled, pale green swellings of variable length on stalks and lower part of midrib of basal leaves. Ditylenchus dipsaci

9a Flower buds strongly swollen, ± globular, about 5–7 mm across, unopened. Several, mainly yellow, non- jumping larvae. Dasineura armoraciae

9b Galls similar, but more slender and smaller, 2–4 mm long. Larvae whitish to pale yellow, jumping. Contarinia nasturtii

Last modified 30.iv.2020