Dichotomous table for gallers on Galeopsis

by Hans Roskam

1a On plant parts above ground => 3

1b On roots => 2

2a Roots with nodular swellings. G. tetrahit: Meloidogyne hapla

2b Roots unaltered externally; inside with giant cells. The bodies of developing female eelworms break through the host tissue and are attached to the root as at first white, then yellowish, eventually partially brown, about poppy-seed sized cysts. G. tetrahit: Heterodera schachtii

3a Galls at tip of vegetative or generative shoots => 11

3b Galls on shoot axis, leaves or flowers => 4

4a Malformations of vegetative organs => 5

4b Flower buds globular, swollen and discoloured, unopened. Containing a white or pale reddish-yellow larva. G. bifida, ladanum, tetrahit: Dasineura tetrahit

5a Galls on leaves distant from shoot tip => 7

5b Galls on axial parts of stem => 6

6a Oblong swelling of upper parts of shoot axis. Shoot tip above swelling usually soon withered. Pith containing many larvae. G. ladanum: Thamnurgus kaltenbachii

6b Conspicuous, usually pale green swelling of basal axial parts; tissue spongy; plant severely stunted. On stems, infected after ± completed longitudinal growth and also on higher situated parts, develop variously shaped galls, on one or all sides, often associated with distortions, ± reddened, spongy. Such galls develop ± locally also on petioles and leaf blades. Galeopsis spp.: Ditylenchus dipsaci

7a Downward roll and distortion of leaves caused by aphids => 8

7b Basal leaf blades with many small, multicellular, wart-shaped, yellowish translucent warts; infestation also encroaching into petioles and stems. G. tetrahit: Synchytrium aureum

8a Aphids up to 2 mm long, dark green, with black siphunculi => 10

8b Aphids yellowish-white or yellow to pale green, or yellow-green with same-coloured siphunculi => 9

9a Aphid 1–1.5 mm long, yellow to pale or yellow-green. Galeopsis spp.: Aphis nasturtii

9 Aphid 2–2.6 mm long, yellowish-white to pale green, with siphunculi of the same colour. Galeopsis spp.: Cryptomyzus galeopsidis subsp. galeopsidis

10a Cauda and siphunculi of the 1.5–2 mm long aphid black, antennae slightly longer than half the body length. Siphunculi and cauda almost of same length. Galeopsis spp.: Aphis frangulae subsp. beccabungae

10b Cauda of the up to 2 mm long aphid green, lighter than siphunculi. Antennae half the body length. Siphunculi twice as long as cauda. Galeopsis spp.: Aphis gossypii

11a Malformations caused by aphids or spittlebugs => 14

11b Galls caused by gall midges, eelworms or gall mites => 12

12a Galls lacking abnormal pubescence => 13

12b Leaves, also flower buds, stunted, clustered on shoot tips; densely pubescent. G. ladanum: Unidentified gall mite

13a Upper leaf pair of shoot tip substantially undeveloped, erect, ± rolled together with the margins, curled. Petiole and leaf blade base markedly stunted, thickened and discoloured with several midge larvae in between. Soon shrivelling after departure of larva, e.g. G. segetum, tetrahit: Macrolabis sp.

13b Stem below inflorescence, also midrib, shortened, spongy, swollen, sometimes severely distorted, ± reddened. Galeopsis spp.: Ditylenchus dipsaci

14a Shoot axis usually terminally infected, stunted and distorted close to infestation site, inserted leaves variously curled and rolled. Galeopsis spp.: Philaenus spumarius

14b Three of the aphid species recorded previously also occasionally colonise the young shoot tips, the axis of which remains ± undeveloped, resulting in a ± nest-like clustering of distorted and paler leaves. Galeopsis spp.:

a Cryptomyzus galeopsidis subsp. galeopsidis

b Aphis frangulae subsp. beccabungae

c Aphis gossypii

mod 24.iii.2020