Dichotomous table for gallers on Filipendula

by Hans Roskam

1a On extensively elongated stems, on buds, leaves or flowers => 2

1b Basal shoots severely stunted and transformed into a large cone-like tough, fleshy gall several cm long, reddish-grey, multi-chambered and bearing rotund lumpy proliferations. Similar but smaller galls also on petioles. F. ulmaria, vulgaris: Dasineura harrisoni

2a On inflorescences or flowers => 20

2b On vegetative parts => 3

3a Galls on stems, midrib of leaf, leaf veins or -blades, caused by animals => 10

3b Shoot axis, petiole or leaf veins with many wart-shaped nodules or with extended swellings; fungus galls => 4

4a Expanded malformations caused by rusts, smuts or mildews => 6

4b The young, still developing parts bear many wart-like galls, hardly 1 mm across, loosely arranged or ± expanded into coalesced crusts => 5

5a Warts consisting of several cells. F. ulmaria, vulgaris: Synchytrium aureum

5b Galls 1-celled, only known from F. ulmaria: Synchytrium ulmariae

6a Galls covered with orange-red spore masses, or also at first unopened with lead-grey translucent blackish spores dusting later on => 7

6b Malformations caused by a white mycelium growing on outside of host. F. ulmaria: Podosphaera aphanis

6c Similar malformations; stems, leaves and shoots thickened and sometimes twisted or otherwise distorted, covered with thick, white mycelium. F. kamtschatica, ulmaria, vulgaris: Podosphaera filipendulae

7a Galls soon covered by orange-red rust sori => 9

7b Galls caused by smuts with spores 1–8 united in easily degraded balls, enveloped by sterile auxiliary cells => 8

8a On F. ulmaria: Urocystis ulmariae

8b On. F. vulgaris: Urocystis filipendulae

9a On F. ulmaria, lobata and relatives: Triphragmium ulmariae

9b On F. vulgaris: Triphragmium filipendulae

10a Large parts of leaf blades disfigured or with localised galls => 13

10b Stems, leaf midrib or leaf veins with localised galls => 11

11a Galls on leaf midrib or leaf veins => 12

11b Weak thickening of shoot axis, mainly close to ground. F. ulmaria: Unidentified lepidopteran

12a Galls hemispherical on upperside, protruding on underside acuminate- conical; wall soft; on midrib or main veins; upperside glabrous and often reddish, underside yellowish, ± pubescent, with terminal, pubescence, narrow exit hole, one-chambered. Containing a single whitish-yellow larva. F. lobata, ulmaria: Dasineura ulmaria

= Various aberrant galls have been described in literature; attributed to either D. ulmaria or undescribed other gall midges. D. harrisoni causes on F. ulmaria in various wet biotopes expanded galls close to the ground.

12b Galls only conspicuous on one side of leaf. Midrib of leaf blade swollen. F. ulmaria: Epitrimerus filipendulae

13a Malformations on leaf blade of leaf => 14

13b Leaf blade deeply dissected at margin, indented, teeth ± narrow fimbriate. F. ulmaria: Unidentified gall mite

14a Leaf blade curled or otherwise extensively disfigured => 16

14b Small grooves or erinea on otherwise unchanged leaf blade => 15

15a On the underside of the slightly disfigured leaf blade occur 1 mm deep grooves in rotund, pale green spots, yellowish margined up to 5 (6) mm across with corresponding archings on upperside. Often many per leaf blade, sometimes coalescing. Each containing a single vitreous, white to greenish larva. F. ulmaria, vulgaris: Dasineura pustulans

= Small grooved galls on F. ulmaria, arched on upper side, which display eggs in the underside cavity, have been attributed to an unidentified psyllid, which may, in strong infestations, also cause a ± distinct curl or upward roll of the leaf margin.

15b On leaf underside between veins, usually close to margin irregular erinea of various dimension with white, club-like hairs. F. ulmaria: Unidentified gall mite

16a Curling or rolling of leaf blade, caused by aphids or spittlebugs => 18

16b Leaf blade with buckled archings or folds, caused by gall midges => 17

17a Bulging yellowish-green to often reddish folds or swellings of the leaf blade, usually elongated and bumpy, often coalescing. Development varies. In cases of strong infestation the leaf blade is strongly curled; occasionally at margin with thickened rolls. Each depression on the underside containing a larva that is at first white, then pale red. F. lobata, ulmaria, vulgaris: Dasineura engstfeldi

17b Leaf blade folded downwards along a lateral vein, white larvae on upper side. F. ulmaria: Dasineura engstfeldi

18a Malformations caused by aphids => 19

18b Shortening of leaf midrib and curling of leaf blade. Filipendula spp.: Philaenus spumarius

= Spiral rolls of stunted basal leaves. The leaflets are densely clustered on the stunted midrib. On the midrib occur bluish-grey, black-headed larvae of an unidentified sawfly

19a Weak arching or curling of leaf tip. F. ulmaria, vulgaris: Macrosiphum cholodkovskyi

19b Various expanded curvings, folds, rolls. F. ulmaria, vulgaris: Aphis ulmariae

20a Flower galls => 22

20b Malformations of inflorescence => 21

21a Often conspicuously disfigured inflorescence covered with a white mycelium: Podosphaera aphanis

21b Stalks of inflorescence distinctly shortened. Buds, and flowers therefore clustered. F. ulmaria, vulgaris: Aphis ulmariae

21c Malformations are also caused by froth-covered nymphs of
Philaenus spumarius

22a Flowers unopened, containing midge larvae => 23

22b Galls on buds and stems of the midge that usually lives on leaves have been attributed to Dasineura ulmaria

23a On F. ulmaria. Flowers swollen on one side in an irregular manner, here densely pubescent, discoloured pale to dark-red; stamens and stem etiolated, galled flowers 1.5–2 mm across, distinguished from healthy flowers by their small size. Larvae white, pale red later on: Dasineura engstfeldi

23b On F. ulmaria. Slightly swollen, unopened red-violet discoloured flower buds: Dasineura spiraeae

23c On F. hexapetala, vulgaris. Flowers unopened, swollen and ± reddened. Larvae red: Dasineura filipendulae

mod 10.ii.2020