Plant Parasites of Europe

leafminers, galls and fungi

gallers on genus Silaum

Dichotomous table for gallers on Silaum silaus

by Hans Roskam

1a On stalks of umbels, flowers or fruits => 6

1b On leaves => 2

2a Localised or extensive malformations caused by animal parasites => 5

2b Small wart-shaped or larger spindle-shaped galls caused by fungi => 3

3a Galls mainly wart-shaped; spores inside host tissue => 4

3b Leaf veins, -midrib or -stalk spindle-shaped, swollen, galls usually conspicuous, sometimes ± curved, often with yellowish margins; bearing dark brown spores. Puccinia angelicae

4a Galls less than 1 mm across, multi-cellular, wart-shaped, ± golden-yellow; usually many on basal leaves, on stalks, midrib as well as on stems; sometimes coalescing into crusts or ridges. In central nutritive cell an up to 180 µm large perennial (“dauer”) sporangium. Synchytrium aureum

4b Galls similar, usually larger, ± black-brown; often clustered into densely situated groups on ± curved leaf veins, -axis or -stalk. Nutritive cells with several, ± rotund, 20–35 x 15–30 µm large perennial (“dauer”) spores. Physoderma vagans

5a Leaf blades and tips of leaflets on the often stunted midrib folded over the midrib or otherwise distorted; ± discoloured and thickened. Containing several yellowish, terminally ± reddened larvae. Jaapiella dittrichi

5b Leaf blade curved; often with curled side leaflets ± clustered, nest-like. Philaenus spumarius

6a On flowers or fruits => 7

6b Centre of (partial) umbel or stalk of umbel ± swollen, club-shaped. Inner wall covered with mycelium. Containing a red larva. Lasioptera carophila

7a Flower bud unopened, swollen to a globular or obovate gall. Unidentified gall midge

7b Fruit disfigured into a bladder-like swollen, often reddened, thin-walled gall, protruding above the partial umbel. Containing 1 (–3) orange-red larvae. Kiefferia pericarpiicola

Last modified 18.xi.2023