Dichotomous table for gallers on Trisetum
(incl. Trisetaria)
by Hans Roskam
1a On above-ground parts => 2
1b Roots sometimes with minor swellings, from which cysts erupt up to 1 mm long, lemon-yellow later on. Trisetum sp.: Heterodera avenae
2a On vegetative organs => 4
2b Galls on ovaries => 3
3a Ovary transformed into an oblong gall protruding far outside the spike. T. flavescens: Anguina agrostis
3b Ovaries within the unopened, not disfigured, glumes strongly elongated, abnormally thin, sometimes conspicuously curved. Each floret containing a pale brick- to orange-red larva. T. flavescens: Dasineura triseti
4a Malformations caused by animals on culms or leaves => 6
4b Leaf blades, rarely sheaths, culms and parts of spikes with several long parallel stripes of smut => 5
5a The long stripes of smut contain a black spore powder. Spores 2–8 in balls, completely enveloped by many sterile auxiliary cells. T. alpestre, flavescens, spicatum: Urocystis triseti
5b The smut mass consists of 8–12 μm single spores. Trisetaria panicea, Trisetum spicatum: Ustilago striiformis
6a On culms => 7
6b Leaf blades ± thickened, longitudinally upwardly rolled inwards and curved, screw-like. T. flavescens: Unidentified tarsonemid mite
7a Culm slightly swollen at base of the ± stunted inflorescence. T. flavescens: Oscinella frit
7b Culm, with weak, slightly rimmed depressions underneath the sometimes slightly arched leaf sheaths, usually close to a node; each containing an orange-yellow larva. T. flavescens: Lasioptera calamagrostidis