Dichotomous table for gallers on Melilotus
by Hans Roskam
1a On above ground parts => 3
1b On roots => 2
2a Nodular or spindle-shaped swellings. M. officinalis: Meloidogyne hapla
2b Globular or up to 8 mm long, cylindrical, forked or coral-like branched nodules. Melilotus spp.: Sinorhizobium meliloti
3a On inflorescences, flowers or fruits => 9
3b On vegetative organs => 4
4a On shoot axis or leaves of fully developed plants => 5
4b Young plants considerably stunted. Stems shortened, spongy, thickened. Leaves clustered, occasionally the axial parts swollen, leaf blades distorted. Melilotus spp.: Ditylenchus dipsaci
5a On shoot axis => 7
5b On leaves => 6
6a Leaflets folded upwards, halves at base ± adnate and swollen, together with midrib, into a globular or oblong gall, up to 6 mm long, protruding on underside. Containing a yellowish beetle larva. M. albus, altissimus, dentatus, officinalis: Tychius crassirostris
6b Weaker swelling of midrib of leaflet. Containing a single larva. M. albus, altissimus, officinalis: Tychius meliloti
7a Inducer inside the gall => 8
7b Acuminate-rotund- to oblong oval, often snapped off, or ± bent, expanded bulging swellings of stem, containing in rimmed depressions the inducer. M. dentatus, officinalis: Planchonia arabidis
8a Rotund to spindle-shaped swelling, 5–15 mm long. The pith containing a maggot. M. albus, dentatus, officinalis: Melanagromyza submetallescens
8b Weak swelling, inside a compact pith containing several white larvae. M. albus: Unidentified dipteran
9a All flowers of a plant occasionally disfigured and ± pubescent. Calyx hardly disfigured, corolla and anthers often reduced, ovary developing into a short, leafy cone, transformed together with the axils of stipules, developing shoots into a ± dense leafy inflorescence. M. albus, altissimus, dentatus, officinalis: Unidentified gall mite
9b Flower buds swollen, unopened. M. altissimus, officinalis: Contarinia sp.
9c Flowers strongly greened; beetle larva living inside stem just below inflorescence. M. albus, altissimus, dentatus, officinalis: Stenopterapion meliloti
9d Beetle larvae feed within the pod on the developing seed; this may cause some galling of the pods. M. albus, ? altissimus, officinalis: Tychius breviusculus