Dichotomous table for gallers on Comarum palustre
by Hans Roskam
1a Galls on vegetative plant parts => 2
1b Flowers stunted, not opening, transformed into ± globular galls. Containing several orange larvae. Unidentified gall midge
2a Leaves strongly curled or with additional pubescence => 3
2b Many spots on both sides of leaf, up to 1 mm across, rotund to angular, usually slightly swollen dark-violet; on petiole developing sori appear as oblong-oval bulges. Nutritive cells distinctly enlarged, with solitary or several (2–4) resting spores. Physoderma comari
2c Leaves are hardly disfigured, but a slight change of colour is discernable.
Bactericera acutipennis
3a Leaves at infestation sites, mainly on underside of leaf, densely silk-like pubescent; grey on corresponding upper side, almost brownish on underside. Phyllocoptes roivaineni
3b Leaf midrib at infestation deflected, severely stunted. Leaflets clustered, nest-like bent downwards, locally strongly crumpled and dark green. Philaenus spumarius