Plant Parasites of Europe

leafminers, galls and fungi

gallers on Origanum

Dichotomous table for gallers on Origanum

by Hans Roskam

1a On vegetative parts => 2

1b Corolla unopened, lower part thickened, leather-like, colourless to brown, up to 4 mm long, 2 mm broad; not joined with the slightly swollen calyx. Containing a single larva. O. vulgare: Asphondylia hornigi

2a Malformations of undefined shape on several organs, mainly at tips of shoots => 4

2b Galls on shoot tips, as well as lateral buds or on axial parts of shoots => 3

3a Shoot axis with spindle-shaped or oblong, bulging, multi-chambered swelling. O. vulgare: Thamnurgus kaltenbachii

3b Small, unilateral stem galls, containing a weevil larva or its pupa. O. vulgare: Squamapion origani

3c Shoot tip or lateral buds transformed into oval tufts of leaves, up to 15 mm long and 10 mm broad, greenish, compact. Leaves broadened, thickened, arched, on upperside often with long white hairs. Containing several red larvae. O. compactum, vulgare & subsp. virens: Blastomyia origani

4a Malformations caused by animals => 5

4b Large parts of plant or only single shoots transformed into little, rigid, erect witches’ brooms as result of excessive branching and leafiness. Diseased shoot axis distinctly narrowed; leaves conspicuously reduced. Brownish sori soon develop on axial parts. O. vulgare: Puccinia thymi

4c Leaf blades, especially of young leaves at shoot tip, with thick purple patches bearing spermogonia and aecia, followed by uredinia and telia. O. vulgare & subsp. virens: Puccinia menthae

5a Malformations lacking excessive pubescence => 6

5b Tip of non-flowering or flowering shoots disfigured; developing ± dense masses of felt-like pubescent leaves, and leafy or greened flowers. O. majorana, vulgare: Aceria labiatiflorae

6a Galls caused by aphids => 8

6b Galls caused by gall midges or spittlebugs => 7

7a Roll of leaf margin caused by gall midge larvae. O. vulgare: Unidentified gall midge

7b Shoot axis buckled, bent locally, bearing several deflected, curled, partially deep green leaves. O. vulgare: Philaenus spumarius

8a Several to many leaves at the end of shoots apically increasingly stunted, laterally ± narrowly rolled, curled. Plants often largely disfigured. O. majorana, vulgare & subspp. gracile + virens + viridulum: Aphis origani

8b Leaves curled. O. vulgare: Aphis nepetae

8c Malformations caused by aphids on terminal vegetative- or developing flowering shoots. O. majorana: Myzus ornatus

Last modified 17.v.2020