Plant Parasites of Europe

leafminers, galls and fungi

gallers on genus Cornus

Dichotomous table for gallers on Cornus

by Hans Roskam

1a On leaves => 3

1b On stems => 2

1c lowers slightly swollen and remaining closed, containing a whitish to light orange larva. On C. sanguinea: Unknown gall midge

2a Small, ± rotund-oval, rimmed depressions on bark of ± swollen twig parts. Cornus spp.: Chionaspis salicis

2b Thick branches with ± spindle-shaped, mistletoe bearing swellings. Cornus spp.: Viscum album

3a Malformations of undefined expansion, caused by aphids or free-living mites => 5

3b Galls of ± defined shape, small, wart-, or pustule-like, or conspicuous, ± blunt-conical => 4

4a Galls larger than 1 mm. Leaves on midrib, mainly on lower side veins, usually with several, 3–5 mm broad, often many-chambered, tough-walled, greenish or ± reddened galls; basally blunt-conical, top surrounded by 2–5 or more lobes; protruding on upper side as a ± hemispherical bump. Each chamber containing a single orange-yellow to -reddish larva. C. mas, sanguinea & subsp. australis: Craneiobia corni

4b Hardly 1 mm long, yellow translucent small warts, usually many on basal green organs. C. sanguinea: Synchytrium aureum

5a Malformations caused by aphids => 7

5b Malformations caused by mites => 6

6a Leaf blade with upward protrusions, usually in vein axils, rarely in other areas. C. mas, sanguinea: Cenopalpus spinosus

6b Leaf blade disfigured, distorted, discoloured; margin ± undulate, almost crenate, rolled upwards. C. sanguinea: Phyllocoptes depressus

6c On underside of usually hardly disfigured, soon ± browned leaves. C. mas, sanguinea: Anthocoptes platynotus and/or Tegonotus acutilobus

7a Aphids yellowish, greenish to red-brownish => 8

7b Aphids black. Terminal leaves ± rolled inwards, slightly curled. C. sanguinea: Aphis fabae

8a Aphid powdered, long haired, on midrib of leaf underside usually arranged in rows. Terminal leaves loosely clustered, nest-like. C. alba, sanguinea, sericea:
Aphis salicariae

8b Aphid not powdered, up to 2.5 mm long. Antennae half the body length. Siphunculi pore-shaped. Leaves, if strongly infected, stunted, curled, rolled, sometimes keel-shaped, deflected. C. alba, glabrata, mas, sanguinea: Anoecia corni

8c Very similar aphid. Causing similar malformations facultatively on C. sanguinea: Anoecia vagans

Last modified 17.xi.2023