Dichotomous table for gallers on Aster

by Hans Roskam

incl. Bellidiastrum, Chrysocoma, Galetella, Symphiotrichum, Tripolium

“Asters” are here incidentally without further designation indicated as hosts for many parasites, especially Meloidogyne-species. It is often not clear which Aster-species, Callistephus [= Aster] chinensis or even cultivated Chrysanthemum-species have been meant by many authors

1a On capitula => 21

1b On vegetative parts => 2

2a Galls less than 1 mm long or with fruiting fungi on the surface => 15

2b Other kinds of malformations caused by animals (or bacteria) => 3

3a Malformations mainly on leaves => 8

3b Galls at the top of main- and lateral shoots or on stems => 4

4a Terminally on plants the growth of which is not stunted => 6

4b Swellings of lower stem parts => 5

5a Stem with considerable, one-sided, ± blistered, smooth-walled, unilocular swelling, Larva without head capsule or legs. Bellidiastrum michelii: Tephritis arnicae

5b Spongy, pale, often massive stem galls with rugose surface. “Aster”: Ditylenchus dipsaci

5c Stem base, still above the underground root collar, swollen; in other areas one-sided, oval, about 10–12 mm long, 3 mm wide; almost on all sides of the thin stems. A yellow caterpillar up to 10 mm with a yellow-brown head capsule. Galetella linosyris: Caulastrocecis furfurella

= Root cankers, caused by Agrobacterium tumefaciens, and “leafy galls” of Rhodococcus fascians have been reported

6a Malformations without conspicuous swellings of the stem => 7

6b Plant growth stunted in longitudinal direction, shoot tip swollen, curved and reddened. One caterpillar. Galetella linosyris, Tripolium pannonicum subsp. tripolium: Eucosma aspidiscana

6c Very conspicuous swelling of twig, containing one caterpillar. Galetella sedifolia: Caulastrocecis gypsella

7a Shoot stem shortened. Abnormal twig- and leaf development on long- or short shoots. Galetella linosyris: Aceria linosyrina

7b On the stunted shoots a rotund gall encased by several leaves, up to 10 mm long, greenish. Larvae between the inner leaves. A. alpinus: Rhopalomyia astericola

8a Leaf blade rolled, folded or curled => 11

8b Leaves with local, ± constant shaped, galls => 9

9a Galls glabrous => 10

9b Whitish pubescent, rotund, spongy, uni- or multilocular galls, up to 16 mm long, yellowish, often many on ± stunted plants, mainly close to basal leaves, more rarely on stem leaves or even on the scales of the capitula. A. alpinus: Unidentified gall midge

10a Leaf blade with greenish-yellow galls, 3–5 mm long, bulging on the underside, about 1.5 mm thick, ± spindle-shaped; often spreading from midrib and occupying or even surmounting the whole leaf blade; sometimes several per leaf, occasionally coalescing. One dark orange-yellow larva per gall. On Galatella linosyris; Tripolium pannonicum: Dasineura linosyridis

10b Cylindrical, up to 20 mm long, 5 mm wide, very thick-walled, tough, multilocular, tubercular gall on leaf base, including the midrib. The upper leaf part folded along the midrib. Tripolium pannonicum: Inducer unidentified – ? gall wasp

11a Leaf blade curved and curled by aphids or cercopids => 14

11b Leaf blade folded or rolled; midge- or mite galls => 12

12a Leaf margin rolled => 13

12b Leaf blade folded downwards, ± bleached. Galatella linosyris: Unidentified gall midge

13a Leaf margin upwardly curved or folded, thickened and bleached. Larvae on upper side. A. alpinus: Unidentified gall midge

13b Leaf blade with loose, weakly thickened leaf margin roll without abnormal pubescence. Bellidiastrum michelii: Aceria opistholia

14a Leaf blade at the margins downwardly curved or rolled, ± strongly curled. Sometimes several leaves densely bunched at the compressed shoot tips. Aphids on the underside. A. amellus and cultivated forms, Bellidiastrum michelii, Tripolium: Brachycaudus helichrysi

14b Leaves, depending on their condition, differently ± strongly curved downwards and curled. Tissue close to the froth-covered nymph dark green. Sometimes several leaves converging spoon- or clump-like on compressed, ± curved stems. A. amellus, Symphiotrichum novae-angliae, novi-belgii including the cultivated forms, S. lanceolatum, Tripolium, etc.: Philaenus spumarius

15a Fungus, infected area larger than 1 mm => 16

15b Many golden-yellow warts, hardly 1 mm long, mainly on the underside of basal leaves. Bellidiastrum michelii: Synchytrium aureum

16a Minor swellings, occupied by brown-black telia => 19

16b Sporangia containing aecia => 17

17a On Bellidiastrum michelii, Tripolium => 18

17b On Galatella linosyris. Sporangia mainly on the underside of the leaves, yellowish, hardly swollen, sometimes bulging the leaf out laterally; also indistinctly swollen callus on the stems about 5–7 mm long: Puccinia linosyridis-caricis

18a On Tripolium. Sori on leaves and stem hardly cecidogenic. Visible malformations only reported laterally on the base of the capitula slightly swollen, ± bent flower head buds. Puccinia extensicola

18b On A. bellidiastrum, hardly cecidogenic aecia: Puccinia firma

19a On A. alpinus, Bellidiastrum michelii => 20

19b On other asters. Sori on the leaf veins or stem parts rotund-oval to spindle-shaped, on sometimes slightly swollen pads. A. amellus, Galatella linosyris, Tripolium, etc.: Puccinia cnici-oleracei

20a Similar sori on A. alpinus: Puccinia asteris-alpini

20b Sori usually in converging, callus-like groups on curved petioles and leaf veins; occasionally on rotund, usually violet-red bordered pads on the leaf undersides. Bellidiastrum michelii: Puccinia bellidiastri

21a Capitula deformed. Receptacle swollen, all- or one-sided. Larvae in receptacle, cylindrically shaped, with black mandibles => 22

21b Capitula hardly swollen. Larvae without conspicuous mouth parts, between flowers. Galatella linosyris: Dasineura procera

= In capitula of Bellidiastrum michelii midge larvae of an undescribed Dasineura have been mentioned.

21c Florets forming a compact rosette of green leaves (phyllanthy); contains mites with four pairs of legs. Symphyotrichum novi-belgii: Phytonemus pallidus

22a Galls preferentially when unilaterally affected ± bent downwards; marginal flowers partially not developed. Tripolium: Campiglossa plantaginis

22b Similar malformations Tripolium: Trupanea stellata

22c In Germany, J. Haase collected inflorescences of Tripolium with many widely extending capitula, of which the flowers were largely reduced and deformed. Cause unknown; similar malformations also known from other Asteraceae, especially Liguliflorae and Cynareae. Might be caused by viruses.

mod 30.iii.2020