Dichotomous table for gallers on Lamium

(incl. Galeobdolon, Lamiastrum)

by Hans Roskam

1a On plant parts above ground => 6

1b On subterranean organs => 2

2a On subterranean stem parts or buds => 4

2b On roots => 3

3a Nodular swellings. Lamium spp.: Meloidogyne hapla

3b Root body normal in external appearance, inside with giant cells; temporarily bearing poppy-seed size white, partially brown cysts. Lamium spp.: Heterodera spp.

3c Rounded pea-size gall on shoot tip or on stolon. L. album, maculatum, purpureum: Dasineura lamiicola

4a Galls predominantly on subterranean buds; caused by gall midges => 5

4b Shoot axis close to or just below ground with ± expanded, strongly swollen galls, up to 10 mm broad, containing black masses of spores. L. album: Melanotaenium jaapii

5a erminal scale-like pairs of leaves of buds of subterranean runners folded together, joined and transformed into a rotund or oblong gall, up to 5 (7) mm long, densely covered with long, white-felt-like hairs. Containing several white larvae. L. galeobdolon: Dasineura strumosa

5b Similar, but larger and occasionally more strongly pubescent galls on subterranean buds, less on side- and end buds of stem. Larvae white, jumping. L. maculatum: Contarinia lamiicola

6a Galls only on flowers => 19

6b Malformation of vegetative organs => 7

7a Malformation of leaves, partially with involvement of shoot => 8

7b Oblong swelling on upper parts of shoot axis; organs inserted above the gall ± shrivelling. Pith containing many larvae. L. album: Thamnurgus kaltenbachii

8a Malformations of leaf, with involvement of expanded parts of terminal shoots => 12

8b Galls only of shoot tips or basal organs => 9

9a Galls of shoot tips => 10

9b Complete plant stunted. The basal stem parts are especially ± markedly shortened, spongy, swollen and pale green. Leaves inserted at infestation site with their stalks and main veins similarly galled. L. amplexicaule, purpureum: Ditylenchus dipsaci

10a Terminal pair of leaves with ± sessile, reduced, erect leaf blades; with several midge larvae between the soon necrotic malformations => 11

10b The terminal, little developed, sometimes ± joined pairs of leaves are transformed into a bud-like, oblong, whitish to yellowish, sometimes ± pubescent shoot tip gall. Containing several white larvae. L. album, flexuosum, maculatum, orvala, purpureum: Macrolabis lamii

11a Shoot tip with erect pairs of leaves with margins rolled inwards and upwards into an elongated, pale-green gall. Containing several white larvae. L. galeobdolon: Contarinia galeobdolontis

11b Between upward folded, curled and thickened leaves occur white larvae. L. maculatum: Contarinia lamii

12a Malformations of undefined shape => 13

12b Corniculate protrusions, up to about 6–8 mm long, tough-walled, pubescent at tip; usually many on leaf upperside. L. album: Dasineura corniculata

13a Malformations caused by aphids => 15

13b Malformations caused by other animals => 14

14a As causer of sometimes ± distinctly swollen leaves, which bend upwards if strongly infected and soon discolour yellowish, then brownish, on L. album, purpureum, has been recorded the free-living gall mite: Aceria lamii

14b Terminal internodes often ± stunted on one side, resulting in ± clustered leaves. Leaf blades at margin ± deflected, curled and dark green close to infestation. Lamium spp.: Philaenus spumarius

15a Malformations by aphids in all gradations of green are so variable that assignment is only possible according to characters of aphids => 16

15b Similar malformations caused by black aphids. Lamium spp.: Unidentified aphid

16a Aphids yellowish-green to dark-green, rotund-oval. Antennae shorter than body. Siphunculi very dark. Surface of wingless forms dull => 18

15b Aphid translucent greenish-white, dorsally with green longitudinal stripes, oblong-oval, glossy. Antennae longer than body. Siphunculi colourless => 17

17a Siphunculi twice as long as cauda. Migrates to Ribes species as primary hosts. L. album, amplexicaule, galeobdolon, maculatum, purpureum: Cryptomyzus galeopsidis

17b Siphunculi as long as cauda or slightly longer. Host alternation absent. Males wingless. L. album, occasionally on L. amplexicaule, maculatum, purpureum: Cryptomyzus alboapicalis

18a Siphunculi as long as cauda. Body yellowish-green. Lamium spp.: Aphis frangulae subsp. beccabungae

18b Siphunculi distinctly longer than cauda. Body dark-green. Host-alternation absent. L. album, amplexicaule, galeobdolon, maculatum, purpureum: Aphis lamiorum

19a Flower buds ± swollen, unopened, up to 7 mm across. Larvae white. L. maculatum: Dasineura lamii

19b Similar galls on L. album. Larvae white to grey. Unidentified gall midge

mod 30.iii.2020