Dichotomous table for gallers on Matricaria

(incl. Tripleurospermum)

by Hans Roskam

1a On above-ground parts => 2

1b Roots with spindle- to nodule- shaped swellings, bearing several lateral roots. Matricaria chamomilla, Tripleurospermum inodorum: Meloidogyne hapla

2a On inflorescences or their organs => 9

2b On vegetative parts => 3

3a Localised galls on leaflets => 8

3b Malformations of leaves, single shoots or the complete plant => 4

4a Various malformations of leaves and shoots => 7

4b Development of entire plant or large parts of it stunted and variously disfigured; caused by aphids => 5

5a Aphids black => 6

5b Aphid yellow to yellow-green, 1.5–2 mm long. Matricaria chamomilla, Tripleurospermum inodorum: Brachycaudus helichrysi

6a More frequent inhabitant of disfigured plants. Matricaria chamomilla, Tripleurospermum inodorum: Aphis fabae

6b Similar development and only distinguished by microscopical characters. Matricaria chamomilla, Tripleurospermum inodorum: Aphis fabae subsp. solanella

6c Dense bushy growth. Matricaria chamomilla: Didymaria matricariae

7a Stems variously spongy, swollen, pale green, with ± rugose surface. Tripleurospermum inodorum: Ditylenchus dipsaci

7b Galls in apical meristems of rosettes and bolting plants, axillary leaf buds. Tripleurospermum inodorum: Rhopalomyia tripleurospermi

7c Downward bend, ± disfigured, locally dark green coloured leaves clustered in sometimes unilaterally curved terminal shoots. Matricaria chamomilla, Tripleurospermum inodorum: Philaenus spumarius

8a Hyaline, pale green, clearly protruding bulges on the leaflets. Tripleurospermum inodorum: Protomyces matricariae

8b Small rotund to oblong, diffuse or coalescing sometimes slightly thickened spots on leaves, conspicuous by their initially white, later on yellow to brown colour. Matricaria chamomilla; Tripleurospermum inodorum, maritimum: Entyloma matricariae

9a Galls in single florets or achenes => 14

9b Malformations on more substantial parts of the capitula => 10

10a Malformations predominantly of the receptacle => 12

10b Malformations predominantly of the florets => 11

10c Galls in different meristematic tissues of flower heads. Tripleurospermum inodorum: Rhopalomyia tripleurospermi

11a Ligules not developed. Flower head transformed into a semi-globular or elongated, 5–50 mm long greened and leafy tuft. Matricaria chamomilla; Tripleurospermum inodorum: cf. Aceria matricariae

11b Ligules elongated and variously curved; tubular florets ± withered. Organs soon covered with a loose grey cover of conidiophores. Matricaria chamomilla, discoidea; Tripleurospermum inodorum, maritimum: Peronospora radii

12a Considerable swelling of the receptacle => 13

12b Receptacle only slightly swollen, ± disfigured, hardened by a beetle larva. Matricaria chamomilla: Microplontus rugulosus

= Larvae of the leafminer Napomyza lateralis are rather frequent in receptacles of Tripleurospermum inodorum

13a Receptacle enlarged, thickened and arched. A yellowish-white maggot. Matricaria chamomilla, discoidea; Tripleurospermum inodorum, maritimum: Trupanea stellata

13b Similar, globular to egg-shaped receptacle gall inhabited by a beetle larva. Matricaria chamomilla; Tripleurospermum inodorum: Omphalapion laevigatum

= Also in capitula of chamomiles the larvae of other snout beetles develop, e.g., Omphalapion hookerorum

14a Single florets transformed into a hard barrel-shaped, glabrous gall, firmly attached to, or embedded in the receptacle, apically opening by a lid. Often several in a flower head. Containing a single larva. Tripleurospermum inodorum: Rhopalomyia syngenesiae

14b Achene swollen and base of corolla enlarged, often several affected in one flower head; each containing a yellow larva. Tripleurospermum inodorum: Ozirhincus longicollis

14c Similar malformations and biology similar to that of O. longicollis. Tripleurospermum inodorum: Ozirhincus hungaricus

mod 27.iii.2020