Plant Parasites of Europe

leafminers, galls and fungi

gallers on genus Arctium

Dichotomous table for gallers on Arctium

(incl. Lappa)

by Hans Roskam

1a Malformations of above-ground parts => 2

1b Root with node-shaped tumefaction. A. lappa: Ceratapion onopordi

1c Gall in root or root collar; spindle-shaped, about 5–10 mm, containing a larva or pupa. A. minus: Cleonis pigra

= Caterpillars of the tortricid Epiblema scutulana, with yellowish brown head, bore into the stem and underground parts. They hibernate in the upper section of their gall cavity. The plant may show a local swelling or shortening of the internodes

2a On leaves => 3

2b Capitula malformed. Larvae in the swollen receptacle. A. lappa, minus, tomentosum: Tephritis bardanae

= Gall-like inflation of the ovary is caused by the tephritid fly Chaetostomella cylindrica

2c Mature achene slightly swollen, with tiny larval entrance hole in upper third and larger hole at base blocked with debris; contains a larva. A. lappa, minus, tomentosum: Terellia tussilaginis

2d Woody galls in capitula. Arctium sp.: Urophora solstitialis

= Hardening and gall-like malformation of the capitula on burdocks might be attributed to the larva of the gelechiid moth Metzneria lappella

3a Leaf blades over extensive areas curled, rolled => 6

3b Leaves with galls => 4

4a Malformations caused by fruiting bodies of fungi situated on the surface => 5

4b Leaves of young plants, close to the ground, on the underside or on the petioles with many ± hemispherical, golden yellow warts, less than 1 mm long. A. lappa, minus: Synchytrium aureum

5a Aecia bearing, ± distinctly upraised yellow bulges on the underside of the leaves; usually on the leaf blades, rotund, up to 10 mm long; less frequently on the main veins, but more conspicuous there, long oval to spindle-shaped. A. lappa, nemorosum: Puccinia silvatica

5b Yellowish, ± oval, 2–5 mm long, weak bulges and curves on the leaf upperside on the main veins. Bulges only on the upperside, soon occupied by cinnamon dusty uredinia. A. lappa, minus, tomentosum: Puccinia calcitrapae

6a Margins of younger leaves rolled inwards, curved and ± curled; older leaves with dark green, slightly bulging spots. Black aphids on the underside. Arctium spp.: Aphis fabae

6b Larger leaf blades with extensive loose downward rolls, mostly obliquely over the top; smaller ± trowel-shaped converging; below close to the froth-covered nymph crooked and tubercular; dark green. Arctium spp.: Philaenus spumarius

Last modified 17.xi.2023