gallers on Setaria

1a Malformations on inflorescences or florets => 3

1b Malformations on leaves, sometimes extending to inflorescence => 2

2a Leaf sheaths swollen; leaf blades variously disfigured. S. pumila: Rhopalosiphum padi

2b Diseased leaves remain rolled inwards, strongly thickened, brittle, at first pale, eventually fraying and releasing reddish-brown oospores. Inflorescence stunted, usually remaining in the leaves; peculiarly leaf-like and greened. S. adhaerens, italica, pumila, verticillata, viridis: Sclerospora graminicola

2c Leaves with long narrow stripes of smut. S. italica: Ustilago striiformis

3a Galls on ovaries caused by smut fungi => 4

3b Spikelets disfigured; sometimes ± greened and leaf-like. Glumes occasionally strongly elongated and rolled. Strong infestation results in bleaching. S. viridis, italica: Aceria tenuis

4a Ovaries swollen, soon filled with black-brown spore masses; spores glabrous, irregular rotund, 8–11 x 6–9 µm, dusty when mature. S. adhaerens, faberi, italica, parviflora, pumila, verticillata, viridis: Ustilago crameri

4b Ovaries strongly swollen. Diseased inflorescences often discoloured grey; appearing compact and thickened. Spores black, with spiny warts, globular to rotund-oval, usually 7–11 µm across. S. adhaerens, pumila, viridis: Macalpinomyces neglectus

4b Ovary hypertrophied by smut fungus. S. pumila: Sporisorium magnusianum