Dichotomous table for gallers on Oenanthe
by Hans Roskam
1a On stems and leaves => 2
1b Centre of umbel or stalk of umbel ± swollen, club-shaped. Inner wall covered with mycelium. Containing a red larva. O. aquatica: Lasioptera carophila
1c Bladder-like fruit galls on O. pimpinelloides: Kiefferia pericarpiicola
2a Galls conspicuous, oval or elongate spindle-shaped => 3
2b Galls less than 1 mm across, multicellular, wart-shaped, yellow translucent; usually many on lower stem parts, petioles, leaf veins and -blades. O. aquatica:
Synchytrium aureum
3a Bulges yellowish, soon bearing aecia. O. aquatica, crocata, fistulosa, globulosa, lachenalii: Uromyces lineolatus
3b Vitreous, yellow-green, unopened bulges of various size on all green parts. O. crocata, fistulosa: Protomyces macrosporus
3c Leaves, especially young ones, blistered and with white down covering underside. O. crocata: Plasmopara baudysii