Plant Parasites of Europe

leafminers, galls and fungi

gallers on Artemisia

Dichotomous table for gallers on Artemisia

by Hans Roskam

1a On above-ground part => 2

1b Roots with nodules, a few mm long swellings, lacking a larval chamber, exhibiting adventitious roots, A. maritima: Meloidogyne hapla

= Similar smooth root galls are known from many countries on other Artemisia species; from which several Meloidogyne species have been determined as causers

2a Malformations of inflorescences and of capitula => 41

2b Malformations of vegetative parts, sometimes encroaching into the inflorescences => 3

3a Rosette- or bud-like, largely closed malformations of rather distinctive shape on shoot tips or lateral buds => 37

3b Plant extensively malformed over various parts, loose malformations of shoot tips or galls on shoot stems and leaves => 4

4a The malformations mainly on the shoot stem or root collar => 23

4b Shoot with extensive malformations, or galls on leaves => 5

5a Leaves with ± defined galls => 12

5b Malformation of the whole plant or many leaves; at the end of the shoots respectively tuft-like clumps of mostly only insignificantly deformed leaves => 6

6a Leaves malformed, at the top of severely stunted shoots ± tuft-like stacked => 11

6b Malformation of many leaves on partially or extensively, stunted stems, however not only stunted at the top => 7

7a Malformations on several or many leaves, at the top of ± shortened shoots; leaves close together; caused by aphids or cercopids => 8

7b The whole plant sometimes with the shoots extensively malformed; all affected parts discoloured. Internodes elongated, often curved. Leaves smaller, malformed, rolled downwards at the margins, bent and twisted; capitula, if present, stunted, deformed, often with ± shortened stems. Extensive branching and phyllanthy. A. campestris, vulgaris: Aceria subtilis

7c Similar malformations of A. vulgaris, displaying also phyllanthy, might be attributed to: Aceria horrida

7d Leaves are disfigured and turn reddish-violet. Artemisia spp.:Aceria tingens

= The gall mite Paraphytoptus paradoxus causes erinea on leaves of A. absinthium

= The gall mite Aceria absinthii causes malformations on leaves and flower heads of A. absinthium

8a Malformations caused by aphids => 9

8b Younger leaves, still growing close to the ground are locally stacked, bent; the closely positioned leaves are ± clump-like converging; locally conspicuously curved and dark green. Containing froth-covered nymph: Philaenus spumarius

9a Leaves slightly rolled inwards or curled, ± stacked => 10

9b Shoots stunted in longitudinal growth. Several leaves in different ways blister-like swollen, rolled together and curled, often very close, stunted, pale green or remarkably reddish. Aphid exuding wax. A. vulgaris: Cryptosiphum artemisiae

9c On A. campestris in similar malformations lives Cryptosiphum brevipilosum

10a Leaf development stunted, yellow spotted or pale green; stacked on the shortened internodes, sometimes in dense clusters; aphid green:

a A. absinthium, vulgaris: Coloradoa artemisiae

c A. campestris in similar malformations: Coloradoa campestrella

c Malformed leaves on A. vulgaris: Macrosiphoniella artemisiae

10b Leaves on the shoot tips similarly malformed, curled, margins ± downwardly bent. A. absinthium: Macrosiphoniella absinthii

11a Shoot tips with small, open tufts of a few folded ± twisted and curled leaves. Containing several bright red larvae. A. vulgaris: Unidentified gall midge

11b Leaves on shoot tips tuft-like stacked, shortened and including the broadened petioles. A. vulgaris: Tingis crispata

11c Terminal parts distorted. A. herba-alba, valentina: Xerobion blascoi

12a Malformations of mainly constant shape of leaf margins and on leaf blades => 13

12b Basal leaves of young plants severely stunted, petioles and basal parts of leaves spongy, inflated, pale green; soon withering. A. campestris: Ditylenchus dipsaci

13a Galls on leaf blade or in venation => 16

13b Malformations of leaf margins or the slender leaf tips => 14

14a Leaf tips or margins locally reverted, discoloured, or often conspicuously reddened. Aphid galls => 15

14b Margin of usually many leaves situated close to the shoot tip, often tightly downwardly rolled over different lengths. A. vulgaris: Aceria marginemvolvens

14c Prominent pustules terminally on both sides of tips of leaf segments; these are sometimes slightly enlarged. A. arborescens: Aceria affinis

15a Leaf tips downwardly rolled; leaf blade bulge-like swollen. Galls usually strongly reddened. A. absinthium, dracunculus, vulgaris: Cryptosiphum artemisiae

15b Leaf tips, also rachis, at the suction sites thickened, yellow green or violet-red coloured; often angular or crooked. A. campestris: Cryptosiphum brevipilosum

16a Galls small, up to ± 1.5 mm long, pock-, nodule-shaped or globular, induced by gall mites => 19

16b Galls larger, about 2 mm long or bigger, midge galls => 17

17a Galls predominantly developed on one side of the leaf blade, slender => 18

17b Galls 2–5 mm long, berry-like, on both sides of the leaf blade distinct. A. campestris incl. subsp. maritima, scoparia: Rhopalomyia baccarum

18a Galls protruding on upper side, about 2 mm long, oblong egg-shaped, acuminate, yellowish or reddish, at top with narrow opening, unilocular; thin-walled, ± transparent; solitary or gregarious; usually on veins. A. abrotanum, vulgaris: Rhopalomyia foliorum

18b Similar galls on A. campestris: Rhopalomyia pseudofoliorum

18c Small ellipsoid galls on leaf axils, leaf blade and rachis, clustered. A. pontica: Rhopalomyia baudysi

18d Galls similar, slightly larger, more acute-cone-shaped, yellowish green or ± reddish, outside strongly pubescent; preferentially on the base of ± stunted leaflets; sometimes on the leaf underside, also in the inflorescence. A. absinthium, genipi, pontica: Rhopalomyia luetkemuelleri

18e Small gall at the vegetative tip with several chambers inside. A. campestris: Rhopalomyia simulans

18f Large globular galls containing midge larvae. A. austriaca: Rhopalomyia saissanica

19a Galls pock- or nodule-shaped, with broad base, less than 1 mm high => 20

19b Galls pimple-shaped, on the leaf upperside, usually many per leaf blade, 1–2 mm long, at the base ± narrowed, often reddened. Opening on the underside, surrounded by hairs. A. eriantha, pontica, vulgaris: Aceria artemisiae

20a Galls flat pimples, glabrous, somewhat protruding, globular or oblong, pale green in the beginning, browned later on; sometimes on petioles or stems => 22

20b Galls nodule-shaped, usually densely whitish pubescent => 21

21a On A. pontica, vulgaris: Aceria pontica

21b On A. austriaca, campestris: Unidentified gall mite

22a On A. absinthium, ? austriaca: Phyllocoptes tenuirostris

22b On A. campestris, vulgaris: Unidentified gall mite

23a Swellings of apical stem parts => 28

23b Galls on root collar or close to the ground => 24

24a Galls several cm long, close to the ground => 26

24b Galls ± globular, close to root collar => 25

25a Swellings of root collar, emerging from a bud; scales ± preserved, ± enclosing a tough-walled gall. One larva inside with black mandibles; or a puparium. A. campestris, scoparia: Napomyza annulipes

25b Buds of stem base developed into ± globular. 4–6 mm long, berry-like, succulent, pale green or reddened galls; occurring solitarily or gregariously. One orange-coloured larva per gall. A. campestris, vulgaris, etc.: Rhopalomyia baccarum

25c Large stem gall, up to 20 mm across, densely white haired, on last year’s stem. Artemisia spp.: Rhopalomyia sp.

26a On A. campestris, maritima => 27

26b On A. vulgaris. Root collar and adjacent stem parts swollen. Containing a single white caterpillar with brown head capsule: Epiblema foenella

27a On A. campestris. Stems usually distinctly swollen at their base; the distal longitudinal growth stunted or completely prevented. Galls up to 60 mm long, 10–12 mm wide; partially concealed in the soil. Containing a single whitish caterpillar with bright- to dark brown head capsule: Cochylimorpha hilarana

= Also reared from more basally situated stem galls on A. maritima

27b Smaller swelling on young twigs. Galls only up to 30 mm long, 3–4 mm wide.A campestris incl. subsp. glutinosa, maritima: Cochylimorpha pontana

27c Spindle-shaped swelling on the stem, development of which is completely stunted, an ovoid gall, 12–13 x 7–8 mm, occupying soon the tip, soon the middle; with a terminal exit hole for the straw-yellow caterpillar. A. campestris incl. subsp. maritima: Cochylimorpha halophilana

27d On A. barrelieri, campestris: Cochylimorpha cultana

27e On A. maritima. Galls also partially in the upper part of the stem, spindle-shaped, up to 20 mm long and 5 mm wide. Containing a single yellowish-white caterpillar: Eucosma krygeri

28a Galls embracing stem, conspicuous, oblong-oval or ± clearly spindle-, tube- or cylinder-shaped, with one- to several larvae inside => 29

28b Cortex of stem with rotund or oblong, sometimes ± coalescing, later on bright brown, pock-like swellings. Infestation sometimes extending to the petiole and leaf blade. A. absinthium, austriaca, campestris, vulgaris: Unidentified gall mite

29a Larvae with distinct head capsule => 32

29b arvae without distinct head capsule => 30

30a Maggots cylindrical, with distinct black mandibles, pupating at feeding site => 31

30b Larvae without mandibles, with sternal spatula. Stem locally stunted, with 10–15 mm long, tube-shaped, abnormally pubescent swelling; leaves stacked. Containing a single orange-yellow larva. A. campestris: ? Rhopalomyia sp.

30c Main shoot with large oblong spindle-shaped, one-chambered swelling, about 20–50 mm long and 15–20 mm thick, initially green and succulent, later brown and woody, inside with a black mass of mycelium. Up to 100 larvae per gall. A. vulgaris: Lasioptera artemisiae

31a Stem with tough, nut-like swelling, up to 15 mm long. A. campestris: Oxyna parietina

31b Upper part of stem stunted, curved and twisted. Pith with several larvae. A. vulgaris: Oedaspis multifasciata

32a Galls more than 10 mm long, containing usually coloured butterfly caterpillars; Head capsule about equal to body width. Shoot growth above the galls usually severely stunted => 33

32b Up to 6 mm long and 3 mm thick acuminated, round-oval, unilocular swellings. Shoot longitudinal growth not stunted. Containing a single larva; head capsule narrower than body width. A. campestris: Taphrotopium sulcifrons

33a Tough, oblong galls on the shoot tips of A. campestris, dracunculus, maritima => 35

33b Extended galls on A. absinthium, vulgaris => 34

34a The higher parts of the shoot stem of A. absinthium, vulgaris stunted; spindle-shaped galls containing thick, yellowish-white caterpillars with a brown head capsule: Eucosma metzneriana

34b Stem of A. vulgaris in the middle part with spindle-shaped swelling, up to ± 40 mm long, 6 mm thick. A yellowish-grey, dark-headed caterpillar in pith canal extending over a considerable distance. Unidentified lepidopteran

35a Caterpillars yellowish to reddish => 36

35b Caterpillar yellowish-white, sometimes tinged pink, with bright- to dark brown head capsule. A. campestris: Eucosma albidulana

36a Caterpillar yellowish or reddish, with dark brown head. A. campestris: Eucosma lacteana

36b Caterpillar yellowish or reddish-yellow with brown-black head. A. campestris, dracunculus: Eucosma wimmerana

37a Galls on the shoot tips of severely stunted stem => 39

37b Bud galls => 38

38a Unilocular, ± rotund, up to 6 mm long, pale green, berry-like succulent bud gall; solitary or with several in the leaf axils, mostly on the lower part of the shoots. One orange-coloured larva per chamber. A. vulgaris, more rarely A. campestris, scoparia: Rhopalomyia baccarum

38b Ovoid swelling covered by leaves. A. herba-alba: Rhopalomyia hispanica

38c Globular woolly gall. A. herba-alba, incana, judaica: Rhopalomyia navasi

38d Development of ovoid acuminate galls at the cost of shoots or leaves, 5–6 mm high, 2 mm wide, glabrous, slightly succulent, tough, becoming at maturity a little woody, red or brown. Contains an initially yellow, later on red larva. A. alba: Rhopalomyia kiefferi

38e Terminal cluster of disfigured and oval leaves, bud-like, enclosing a little ovoid larval chamber. Contains a single larva. A. campestris incl. subsp. variabilis, scoparia, vulgaris: Rhopalomyia artemisiae

38f Lateral buds changed into rotund, rather tough walled, dark coloured galls about 3 mm long. Galls situated at different height on the stem, mainly in the lower part. A. vulgaris: ? Rhopalomyia sp.

= The tephritid Ptiloedaspis tavaresiana may cause bud galls on A. herba-alba.

39a Leaves in tufts; gall chambers invisible from the outside => 40

39b Shoot tip with several close, cylindrical-cone-shaped galls, up to 15 mm long, tough walled, ± violet, white pubescent. Opening at the tip, closed by hairs, encircled by spreading, pubescent teeth. Containing a single white larva per chamber: A. campestris incl. subsp. glutinosa: Rhopalomyia tubifex

39c Shoot tips, with several small, rotund to oblong-oval, bold galls. Containing a single larva per gall. A. pontica: Rhopalomyia baudysi

39d Small galls of various form on leaves, leaf stalks and stems. Each gall containing a single red midge larva. A. arborescens: Rhopalomyia protrahenda

40a Apex of main- and lateral shoots with ± ovate or almost globular, bud-like closed tufts. Leaf segments shortened and broadened. Galls in the lower part sometimes with ± silk-like pubescence; the inside with several small, oblong chambers, open at the apex, with translucent wall. Galls with only a central chamber about 3–4 mm long, if multilocular up to 15 mm wide; often overgrown by lateral stalks of the inflorescence. Containing a single larva per chamber. A. campestris, scoparia: Rhopalomyia artemisiae

40b From small, similar globular shoot tip galls is also described Rhopalomyia campestris

40c Leaves at the shoot tips in tufts and abnormally pubescent. One orange-coloured, glossy larva. A. austriaca, campestris, scoparia: Unidentified gall midge

= Abnormally pubescent stunted shoot tips or lateral buds on A. campestris are caused by the gall midge Rhopalomyia jaapi.

40d Tuft terminally on shoot, composed of young branches and curled leaves. A. arborescens, campestris, vulgaris: Aceria subtilis

41a Malformations of capitula caused by gall midge- or tephritid larvae => 45

41b Malformations of capitula or inflorescences by gall mites => 42

42a Malformation of capitula not in abnormally shortened inflorescences => 43

42b Capitula of the severely stunted inflorescences concentrated in thick, spike-shaped clumps, often purple-red coloured. A. vulgaris: Unidentified gall mite

43a Capitula enlarged, rotund; florets ± tongue-shaped deformed, greenish => 44

43b Involucre of the flower head distinctly elongated, twisted at the top. Flowers aborted. A. campestris: Unidentified gall mite

43c Subglobose malformations on the flowers which are normally shaped further on, but are reddish coloured. A. alba: Aceria artemisiae

44a Galls on A. campestris: Aceria subtilis

44b Similar galls on A. vulgaris: Aceria horrida

45a Galls caused by slender midge larvae lacking conspicuous mandibles => 47

45b Receptacle swollen, ± hardened. Containing a single yellowish-white, cylindrical larva with distinct mandibles. A. absinthium: Trupanea stellata

45c Flower head swollen. A. campestris subsp. maritima: Tephritis dioscurea

45d Flower head swollen. A. vulgaris: Campiglossa absinthii

46a Galls on A. campestris, genipi => 49

46b Galls on A. vulgaris => 47

46c Galls on A. herba-alba. Cylindrical gall, 9 x 3 mm, wall finely pubescent and covered with many bracts; inside an oblong large chamber which is closed by a tuft of white hairs and a crown of bracts. Containing a single orange larva: Rhopalomyia producticeps

46d Galls on A. herba-alba. Axillary buds changed into small galls, 6 x 4 mm in size, each gall is composed of many very small leaves, inside a chamber with one larva. Usually many galls occur on one attacked stem: Rhopalomyia ambrosinae

46e Large galls on stems. Globular galls, up to 10 mm, densely white pubescent, situated on stem sides; several chambers occur inside one gall. Only one larva in each gall. Galls may coalesce in large forms, up to 40 mm. A. herba-alba: Rhopalomyia navasi

46f Small galls on stems. Swollen buds, egg-shaped, fleshy, reddish coloured, surrounded with deformed leaves, with a small ovoid gall in its centre. A. herba-alba: Rhopalomyia hispanica

47a Capitula enlarged, ovate or blunt slender conical => 48

47b Capitula ± globular; one large central gall. Containing a single deep yellow larva. Anthodiplosis rudimentalis

= The midge larvae of Blastodiplosis artemisiae, living in the galls, should be considered either as inquilines or as parasitoids of Anthodiplosis

48a Capitula weakly thickened, containing yellow, jumping larvae: Contarinia artemisiae

48b Capitula slightly enlarged and elongated, truncated at the top, ± red-coloured. Between the flowers an ovate, translucent gall containing a single larva: Rhopalomyia florum

48c Also from weakly thickened capitula have been recorded: Rhopalomyia magnusi

49a On A. campestris => 50

49b On A. genipi. Inflorescence often shortened. Small, ± acuminate ovate, at the outside pubescent, tough-walled galls on involucral bracts, also in deformed flowers. Containing a single larva: Rhopalomyia luetkemuelleri

50a Malformation of single, or several adjacent, capitula without externally recognisable gall chambers => 51

50b Capitula extensively changed into a consistent large gall ± cylindrical, up to 12 (15) mm long, with some green leaflets on the outer side. Wall of gall firm, ± violet-white pubescent, with extending leaf-like teeth at the top; entry closed by hairs. Containing a single white larva: Rhopalomyia tubifex

51a Capitula extensively reshaped, rounded, bud-like, consisting of ± ovate leaflets, which enclose an oblong, translucent walled gall body. In very compressed shoots several gall bodies sometimes appear superficially to be unified. Containing a single larva per gall: Rhopalomyia artemisiae

51b From similar galls in shoots and capitula have been recorded: Rhopalomyia campestris

51c Capitula weakly swollen; containing orange-yellow larvae between stunted organs: Dasineura artemisiae

= The non-cecidogenic Puccinia tanaceti with uredinia and telia is abundant on the underside of the leaves.

Last modified 27.ii.2023