Dichotomous table for gallers on Helleborus
by Hans Roskam
1a Malformations caused by fungi with erupting or clearly transparent sori => 4
1b Malformations caused by animal inducers or fungi with fruiting bodies which are not apparent externally => 2
2a Pustule-shaped or minor bulge-like swellings on stems and leaves => 3
2b Leaf blades ± twisted, with margins downwardly deflected. H. foetidus, lividus & subsp. corsicus, niger, orientalis, purpurascens, viridis & subsp. bocconei: Macrosiphum hellebori
3a Leaf blade, more rarely petiole, with pustule-like necrotic oval swellings, up to 3 mm long, visible on both sides or on underside only; usually in two rows along the midrib. Each pustule containing a greenish-white egg; after emerging the larva lives freely on the leaf blade. “Procecidium” (oviposition scar, not a true gall). H. foetidus, niger, viridis: Monophadnus latus
3b Weak, at first ± vitreous, spindle-shaped swellings on stems and petioles. H. viridis: Physoderma deformans
4a Galls caused by rusts and smuts => 5
4b Galls caused by false mildew. Systemic infection of overwintering mycelium in rhizome. The diseased leaves are smaller, yellowish, the segments ± distinctly spoon-shaped downwardly deflected and curved; soon covered by a widespread, dense layer of conidia. H. dumetorum, foetidus, niger, odorus, purpurascens, viridis & subsp. istriacus: Peronospora pulveracea
5a Initially grey translucent smut bulges of variable size on all green parts, soon erupting and with black dusting. Helleborus spp.: Urocystis floccosa
5b Yellow aecia pads associated with spermogonia on gall-like swollen, sometimes ± bent petioles and leaf blades. Helleborus spp.: Puccinia actaeae-elymi
5c In similar aecia. Helleborus spp.: Puccinia actaeae-agropyri