Plant Parasites of Europe

leafminers, galls and fungi

gallers on Mentha

Dichotomous table for gallers on Mentha

by Hans Roskam

1a On parts above ground => 2

1b Nodular swellings on roots bearing side roots. Mentha spp.: Meloidogyne hapla

2a On inflorescences or flowers => 12

2b On vegetative organs => 3

3a Various malformations on shoots or leaves => 7

3b Localised galls of different size on stems or leaves => 4

4a Wart- or bulge-shaped galls caused by fungi => 5

4b Egg-shaped or conical galls, 4–6 mm long, 2–3 mm thick, often reddened swellings of shoot axis, usually situated above a higher node. Containing a curved larva, yellow when mature. M. aquatica, arvensis, pulegium, suaveolens: Squamapion vicinum

5a Galls contain spores => 6

5b Strongly swollen, sometimes conspicuously curved, yellowish or brownish-green bulges on basal stem parts; pads on leaf blades protruding on underside, on upperside often ± depressed, yellow, ± red-margined. Galls soon bearing cups, with dust of reddish-yellow spores. Mentha spp.: Puccinia menthae

6a Less than 1 mm long, golden-yellow translucent, multi-cellular warts on leaf underside, on petioles and stems; often many and occasionally joined into crusts or ridges. M. aquatica, longifolia: Synchytrium aureum

= On leaves of M. aquatica small, irregular globular or oval, often reddened nodules with a central cavity may be caused by the green alga Chlorochytrium rubrum.

6b Thick, black-brown bulges on stems, rarely on leaves, containing dark brown spore masses. M. aquatica: Physoderma menthae

7a At shoot tips or on leaves => 8

7b Plants stunted. Stem at base with bases of inserted leaves strongly swollen and spongy. Gall ± pale-green, necrotic. Mentha spp.: Ditylenchus dipsaci

8a Malformations not excessively pubescent => 10

8b Malformations covered by dense, abnormal pubescence => 9

9a Leaves or, if present, also neighbouring flower buds stalked on tips of main- and side shoots; all organs with ± dense yellowish-white pubescence on all sides. Hairs multi-cellular, branched. Sometimes excessively leafy, branched. Mentha spp.: Aceria megacera

9b Leaf blades of slightly stunted leaves with dense whitish pubescence. M. aquatica, arvensis, longifolia, mollissima, spicata: Aceria mentharia

10a Malformations caused by aphids => 11

10b Clustering of several leaves on bent shoot tips, usually stunted on one side and ± rolled and curled. Mentha spp.: Philaenus spumarius

11a Leaves on shoot tip strongly curled. Aphid green. Mentha spp.: Aphis affinis

11b Leaf blades of terminal leaves strongly curved and deflected. Aphid greenish-white. Mentha spp.: Ovatus crataegarius

12a Malformations of inflorescence => 14

12b Malformations on single or several flowers => 13

13a Flower buds swollen, unopened. Inner wall with mycelium. Containing an ochre-yellow larva. Mentha spp.: Asphondylia menthae

13b Flow ers slightly disfigured, only recognisable if closely examined. Mentha spp.: Peronospora stigmaticola

14a Malformations abnormally densely pubescent => 15

14b Malformations without abnormal pubescence. Accumulations of slightly stunted bracts and severely disfigured flowers at shoot tip of Mentha spp.: Eriophyes menthae

15a Flowers, mainly of terminal inflorescences, transformed into dense, white-pubescent, greened structures. Mentha spp.: Aceria megacera

15b Similar galls on M. arvensis, longifolia: Aceria mentharia

Last modified 1.iv.2020