Plant Parasites of Europe

leafminers, galls and fungi

gallers on Festuca

Dichotomous table for gallers on Festuca

incl. Schedonorus, Vulpia

by Hans Roskam

1a Galls on restricted organs and parts of organs => 3

1b Malformation of expanded parts of the above-ground plant => 2

1c Red midge larvae living on roots. Schedonorus pratensis: Lasioptera auricincta

1d Roots with aphids. Festuca spp.: Tetraneura caerulescens

2a Complete plant stunted, only a few cm high; shoots at base onion-like, swollen. Leaf sheaths accordingly shortened, weakly swollen and broadened. Schedonorus pratensis: Chlorops sp.

= In severely stunted, over expanded spongy, swollen areas of young plants the polyphagous stem eelworm Ditylenchus dipsaci has occasionally been found.

2b Complete plant stunted. Upper leaf sheath distinctly widened, transversely folded and bulging. F. rubra: Unidentified tarsonemid mite

= Malformations attributed to the polyphagous mite Steneotarsonemus spirifex has been reported by for several fescues.

3a On above-ground plant parts => 4

3b Roots with swellings about 0.5–3 mm long, slender, screw-shaped or crooked. Festuca ovina, Schedonorus pratensis: Subanguina radicicola

= Also the cyst developing oat eelworm Heterodera avenae has been recorded on fescue

4a On leaves, inflorescences or flowers => 11

4b On culms => 5

4c Node of stem rarely swollen, encircled by fungus stroma, yellowish when mature; several nodes may be affected; flowering stunted; stroma containing narrow asci and filamentous spores. Festuca rubra: Epichloë festucae

5a Larvae are inside the galls => 10

5b Larvae between culm and leaf sheath => 6

6a Larvae in shallow covered depressions of the culm near the leaf sheaths => 7

6b Shoot severely stunted. Inflorescence often largely hidden in sheath. Culm at base of inflorescence sometimes ± swollen. Containing a single larva. Festuca rubra, Schedonorus arundinaceus, pratensis: Oscinella frit

= On Festuca rubra, Schedonorus pratensis lives the similar Oscinella vastator. On F. rubra, O. nitidissimaoccurs. On the culms of Schedonorus arundinaceus subsp. orientalis and Schedonorus pratensis, the closely related polyphagous Oscinella pusilla, and on Schedonorus arundinaceus, giganteus, pratensis, also recorded from Leymus, the widely distributed rarer Oscinella festucae

= On Festuca ovina, rubra stem galls incorporating leaf sheaths have been reported caused by Tetramesa brevicornis.

7a Depressions not conspicuously discoloured => 8

7b Black-coated, one-sided, expanded, irregular depression with orange-yellow larva, usually above the last node. F. rubra: Hybolasioptera fasciata

8a Depressions evenly weakly rimmed all around => 9

8b Depression particularly saddle-like, thickened at the ends, single or with several above the higher situated, predominantly last node. Each gall containing a bright red larva. Schedonorus pratensis: Haplodiplosis marginata

9a One to several laterally hardly swollen depressions of the culm. Each containing a single larva. Schedonorus arundinaceus: Lasioptera calamagrostidis

9b Base of young shoots sometimes, if many larvae or puparia present, slightly swollen. Larvae yellowish-white, ± 3 mm long; puparia flax seed-like; within a leaf sheath. F. rubra: Mayetiola festucae

10a Galls tapering at both ends, spindle-shaped, wall rugose, surface glabrous. Festuca spp.: Tetramesa brevicollis

10b Irregular, yellowish-green swellings of culm above the nodes. Festuca spp.: Tetramesa longicornis

11a Malformations on inflorescences, flowers or young fruits => 16

11b Malformations on leaf sheaths or -blades => 12

12a The malformations extend over substantial parts of the leaf => 13

12b Leaf blade with 1–2 mm broad, slender egg-shaped to bulging swellings, mainly on underside, often discoloured red- to blue-violet. Festuca spp.: Anguina graminis

= From Festuca ovina, rubra, Schedonorus pratensis the sac fungus Dilophospora alopecuri, which is associated with eelworms on several grasses, has been recorded.

13a Stripes caused by black-sporulating smut on leaf blade, occasionally also on sheath => 14

13b Malformations caused by aphids. Leaf sheaths ± bulging and swollen, leaf blades variously twisted and rolled inwards. Schedonorus pratensis: cf. Rhopalosiphum padi

14a Spores single => 15

14b Spores single or more rarely 2–3 in balls enveloped by sterile auxiliary cells. F. ovina, rubra: Urocystis ulei

15a Stripes of smut very long, fine; at first lead-grey, then yellowish-grey. Spore mass black-brown. Spores globular to rotund-oval, 20–30 x 18–24 μm. Wall yellowish-brown, with lighter patches. F. ovina: Tilletia sterilis

15b Patches of smut long, linear. Mass of spores almost black. Spores globular to rotund-oval, 10–16 x 8–14 μm; densely covered with small blunt warts. Festuca spp.: Ustilago festucarum

16a Malformations mainly on large parts of the inflorescence => 17

16b Single or several ovaries per inflorescence are distinguished by a pronounced bottle- or tube-shaped, often purple-red elongation; containing eelworms. Festuca spp.: Anguina agrostis

16c Red midge larvae develop in florets and seed cases without inducing galls. Festuca rubra, Schedonorus arundinaceus: Dasineura festucae

17a Stem parts of the exposed panicle shortened apically, or over the whole inflorescence, bearing ± disfigured flowers or spikelets. Festuca spp.: Aceria tenuis

17b Gall midge larvae live in the inflorescences. Festuca rubra, Schedonorus arundinaceus: Contarinia festucae

Last modified 8.ii.2020