Plant Parasites of Europe

leafminers, galls and fungi

gallers on Saxifraga

Dichotomous table for gallers on Saxifraga

by Hans Roskam

1a In inflorescences, on flowers or their parts => 10

1b On stems and leaves => 2

2a Extensive or limited malformations on leaves, or localised swellings on stems => 4

2b Malformations involve extended parts of shoots => 3

3a Shoot tip disfigured, shortened, ± abnormally haired. Inflorescences, if present, with disfigured, leafy flowers. Excessive branching and leafiness. S. aizoides, mutata: Aculus kochi

3b Internodes shortened. Leaves on shoot tips clustered. Infected inflorescences disfigured. Flowers leafy. Mites free-living on organs. S. oppositifolia: Aceria saxifragae

4a Localised wart- or bulge-shaped galls caused by fungi => 7

4b Extensive malformations on leaves, sometimes on stems => 5

5a Malformations caused by animals => 6

5b Diseased leaf blades smaller, narrower, and paler than the healthy ones, and slightly thickened; on underside large areas are covered with loosely arranged, yellow sori. Buds, stem parts or inflorescence stalks, infected during development ± stunted and slightly swollen. S. cespitosa, granulata: Melampsora vernalis

6a Petiole of several rosette leaves shortened and spongy; leaf blade stunted and especially lower half, especially the veins, wrinkled, pale green. S. umbrosa: Ditylenchus dipsaci

6b Curling of basal leaves. S. granulata: Unidentified aphid

7a Galls pad- or spindle-shaped, several mm in size => 9

7b Galls wart-shaped, less than 1 mm long; sometimes ± coalescing => 8

8a Warts very small, punctiform, 1-celled, crimson-red. The nutritive cell protrudes only a little from the leaf surface, merely extending inside the host tissue. S. granulata: Synchytrium rubrocinctum

8b Nutritive cells enlarged, including neighbouring cells. Galls ± yellowish. S. aizoides, androsacea, bryoides, moschata, stellaris: Synchytrium saxifragae

9a Sori ± whitish- to greenish-yellow, visible on both leaf surfaces. Only exceptionally slightly swollen. Chlamydospores inside leaf, conidia developing on surface. S. ? aizoides, rocheliana, rotundifolia: Entyloma schinzianum

9b Similar infestations on S. paniculata, aspera, bryoides, oppositifolia: Arcticomyces warmingii

9c Sori dark brown, powdery or nodular, mainly prominent on underside, bulge-shaped swellings on leaf blade, leaf veins, -stalks; on stems in ± bulging sori causing distortions and bends. Teliospores striate. Saxifraga spp.: Puccinia saxifragae

10a Galls on flowers or ovaries => 11

10b Inflorescence ± shortened, spirally rolled inwards. S. paniculata: Unidentified lepidopteran

11a Malformations of ovary, containing a single midge larva => 13

11b Flowers ± leafy or swollen and unopened => 12

12a Flowers leafy, transformed into small rosettes. S. biflora, oppositifolia: Aceria saxifragae

12b Flower buds ± strongly swollen; broad egg-shaped, ± reddened, unopened. Containing several sulphur-yellow larvae. S. granulata: Dasineura saxifragae

13a Ovary greatly enlarged, thick-walled. Style stunted. Containing single pale red larva. S. aizoides: Unidentified gall midge

13b Ovary weakly swollen; infected flower shorter and more compact than the normal ones. Containing yellow-red larva. S. granulata: Unidentified gall midge

Last modified 12.iv.2020