Plant Parasites of Europe

leafminers, galls and fungi

gallers on Knautia

Dichotomous table for gallers on Knautia

by Hans Roskam

1a On inflorescences or flowers => 10

1b On vegetative parts => 2

2a Locally restricted malformations => 3

2b Complete plants ± stunted, organs variously disfigured. K. arvensis, dinarica, dipsacifolia, drymeia, longifolia: Aphis confusa

3a Malformations terminally on main- and side shoots or on leaves Malformations terminally on main- and side shoots or on leaves => 5

3b Galls only on axial parts of shoot => 4

4a Shoot axis often thickened below inflorescence and densely haired. K. arvensis: Ditylenchus dipsaci

4b Usually basal part of stem with conspicuous, spindle-shaped or irregularly bulging and ± buckled swellings, with single or several rimmed depressions; containing the causative froth-covered nymph under a bulging scale. K. arvensis:
Planchonia arabidis

4c Gall-like malformations on shoots of K. longifolia: unknown galler

5a Galls on leaves => 8

5b Galls terminally on shoots => 6

6a Galls restricted to shoot tips => 7

6b Variously shortened internodes on shoot tips, often predominantly one-sided, causing the leaves to cluster on ± curved stem; leaf blades stunted, ± deflected and curled, deep green close to the froth-covered nymph. K. arvensis, drymeia: Philaenus spumarius

7a Terminal leaves folded together, haired. Containing several white larvae. K. arvensis, dipsacifolia, drymeia, transalpine: Jaapiella knautiae

7b Terminal pair of leaves ± unfolding, completely thickened or only at base, folded together upwards, pouch-like; densely pubescent with rigid hairs. Containing a single yellow midge larva. K. arvensis, collina, drymeia: Unidentified gall midge

8a Galls only in leaf blade of basal leaves => 9

8b Petiole and midrib with pale yellow-green, spongy swellings, variously encroaching onto ± disfigured leaf blade. K. arvensis: Ditylenchus dipsaci

9a Very weak protrusions on underside in vein axils, hardly visible on upper side. K. drymeia, longifolia: Trioza munda

9b Up to 5 mm long, yellow, slightly protruding, often many pustules on leaf blades. Containing a single lemon-yellow larva. K. arvensis: Unidentified gall midge

10a Malformations caused by fungi => 12

10b Malformations caused by animals => 11

11a Malformations of flowers caused by jumping, whitish- to orange-yellow midge larvae. K. arvensis, drymeia: Contarinia dipsacearum

11b Capitula ± disfigured and weakly swollen. Containing a single caterpillar. K. arvensis: Stenoptilia bipunctidactyla

12a nfected flowers often of different colour, partially strange-looking. Several petals enlarged and disfigured; number enlarged by ± largely transformed stamens. anthers and ovaries mostly aborted. K. arvensis, dipsacifolia, drymeia, kitaibelii: Peronospora violacea

12b Diseased capitula almost half-globular. Involucral bracts normal; young flowers unopened for a relatively long time, often distinguished by early discolouration of all capitula of diseased plants. K. arvensis, dipsacifolia, drymeia, longifolia, pancicii: Microbotryum scabiosae

12c The anthers are transformed into a purplish-brown powdery mass of spores. K. arvensis, dipsacifolia: Microbotryum flosculorum

Last modified 17.iv.2020