gallers on genus Hesperis

1a Galls on stems, leaves, flowers or fruits => 2

1b Swellings on roots, up to several cm long, 5–10 mm wide. Hesperis spp.: Plasmodiophora brassicae

2a On flowers or fruits => 6

2b On stems or leaves => 3

2c Malformation of all organs caused by mildew. H. matronalis: Albugo candida

3a On leaves => 4

3b Shoot axis on root collar with rotund, one-chambered fleshy swellings, sometimes with several coalesced, hence multi-chambered, bulging. H. matronalis: Ceutorhynchus assimilis

3c Cancer-like galls. H. matronalis: Agrobacterium tumefaciens

4a Rolled margins or curling of leaf blade => 5

4b Petiole or midrib with spindle-shaped swelling, up to 15 mm long, often deep green. H. matronalis, nivea: Ceutorhynchus chalybaeus

4c Leaf underside with a greyish down of erect conidiophores that distally are several times branched. At each tip an egg-shaped conidium. H. matronalis: Hyaloperonospora hesperidis

5a Leaf margin at leaf blade base, often up to the middle of the leaf blade or farther with 2 mm wide, compact roll. H. matronalis: Inducer unknown

5b Loose roll of leaf margin or upward fold of leaf blade. H. matronalis: Brevicoryne brassicae

6a Flower buds swollen, unopened. H. laciniata, nivea: Cause unknown – ? gall midge

6b Fruit locally disfigured, sometimes bent and swollen. H. matronalis: Inducer unknown