gallers on Oenothera

1a On parts above ground => 2

1b Nodular, almost rotund galls on roots. O. fruticosa: Meloidogyne hapla

2a Expanded malformations on single or several organs => 4

2b Small wart-shaped galls on leaves and stems => 3

3a Warts multicellular, orange to crimson-red translucent, often densely clustered, mainly on basal plant parts. O. biennis: Synchytrium fulgens

3b Warts multicellular, glass bead-like. O. biennis: Synchytrium mercurialis

4a Causers on host surface and visible with naked eye => 6

4b Causers inside galls or, if on outside, only microscopically => 5

5a Outer rosette leaves stunted and disfigured. Midrib spongy, swollen. Neighbouring leaf blade areas undulate-lacerate. O. biennis: Ditylenchus dipsaci

5b Malformation of complete, severely stunted plants with partially greened flowers. O. biennis: Inducer unknown

6a Axial parts of shoots stunted or curved on one side; leaves ± clustered, deflected over tip and margins, ± curled and locally deep green. Oenothera spp.: Philaenus spumarius

6b Plant distorted, shoot axis shortened. Leaves smaller, folded between side veins, also ± curled. Flowers greened and thickened Oenothera spp.:
Brachycaudus cardui

=Aphis holoenotherae has been recorded from many Oenothera species. This is the only aphid that is fully dependent on evening primrose. Not a true gall causer