Plant Parasites of Europe

leafminers, galls and fungi

gallers on Phragmites

Dichotomous table for gallers on Phragmites

by Hans Roskam

1a On vegetative plant parts => 2

1b Ovary infected by smut fungus: Neovossia danubialis

1c In florets; a solitary pinkish larva replacing the ovary. Unidentified gall midge

2a On shoots, leaf-blades or -sheaths => 6

2b On lower internodes of the culm => 3

3a Culm distinctly or weakly swollen => 5

3b Galls inside the culms, which are not remarkably changed on the exterior => 4

4a Wall of the culm with single or many grain-like swellings, oval to spindle-shaped, rarely over 6 mm long, thin- and later tough-walled, unilocular; mostly protruding inside the culm, if heavily infected also protruding externally on the ± turgid culm. One white to orange-coloured larva per gall: Giraudiella inclusa

4b Rarely visible swelling on the clearly stunted culm. Larvae solitary in separate chambers in pith, which are sometimes present in large number per internode: Tetramesa phragmitis

5a Culm in the non-flowering unshortened upper part slightly swollen. Many orange-coloured larvae present in the dark or black pith. Infestation often inconspicuous: Lasioptera flexuosa

5b Several internodes of the culm, occasionally also the rhizomes, shortened and sometimes noticeably swollen beyond the normal diameter. Body of the gall sometimes constricted at the nodes; therefore reminiscent of slim concatenate spadixes of Typha. Covered for a long time by the black-brown sori, which remain closed until spores are released at about flowering time: Ustilago grandis

6a Galls in or on the shoot tips => 7

6b Leaf blades of the younger, already ± unfolding leaf blades rolled over their length and bleached: Hyalopterus pruni

7a The galls develop on the shoot tips as swellings of the culm => 9

7b The galls develop partially or completely from terminal leaves of the shoot => 8

8a Internodes compressed at the shoot tip; the adjacent youngest leaves swollen, transversely and longitudinally folded, ± twisted; the inwardly facing epidermal cells developed into club-shaped, brown, hairs in dry conditions. Usually the upper part gradually narrowed, heavily wrinkled, sometimes covered by normal leaf blades, gall breaks with its basal parts in ± buckled curves through the enveloping leaf sheaths: Steneotarsonemus phragmitidis

8b Leaves and the stunted, non-leafing shoot tips similarly deformed. Infected parts usually less swollen. Gall at its base often likewise curved and protruding. Club-shaped hairs absent. Between the swollen, dark coloured parenchyma are many dark orange-coloured gall midge larvae: Giraudiella inclusa

9a On the tips of main shoots => 10

9b Longitudinal growth of lateral shoots ± stunted, deformed to 15‒30 (50) cm long obliquely ascending slightly spindle-shaped swollen, tough-walled shoots. Leaf sheaths well developed, ± gaping, the closely converging leaf blades markedly shortened. In the dark brown to blackish coloured pith are many white to bright reddish-yellow gall midge larvae living in isolated chambers: Lasioptera arundinis

10a Gall usually less than 8 cm long and slim => 11

10b The characteristic “cigar” galls are up to 15 cm long and 1.5 cm wide. Terminal internodes markedly shortened and swollen; cross walls are missing in the older, initially still green galls which, from autumn onwards, turn brown and woody. Leaves converging, sheaths well developed, tight fitting, development of leaf blades variable, often considerably stuntedA fat, in mature condition 7‒10 mm long, cylindrical white-yellow maggot lives inside the tube-shaped chamber: Lipara lucens

11a Especially in the stem parts less conspicuously developed gall without chamber and no thickening of the stem. Wall hardly lignified. Sheaths spindle-like swollen; leaf blades usually normally developed, clearly separate from the gall. The larva lives between the leaf sheaths growing from the two terminal nodes, its position marked by a dark brown rotting channel: Lipara similis

11b Gall slender, c. 1.8 x diameter of normal shoot, central chamber not woody. The upper leaf is not normally developed but shortened and remains ± boat-shaped. Leaf sheaths broadened; leaf blades of the lower leaves normal, dropping off in autumn. Larva situated above growing point: Lipara rufitarsis and/or L. pullitarsis

Last modified 30.iv.2020