Plant Parasites of Europe

leafminers, galls and fungi

gallers on genus Juglans

Dichotomous table for gallers on Juglans regia

by Hans Roskam

1a On leaflets of leaves => 4

1b On axial parts of shoots => 2

2a The causers of malformations are on the outside => 3

2b Axial parts of shoots, especially on young plants, with rotund proliferations, up to fist-size, with fissured surface. Agrobacterium tumefaciens

3a Bark of twigs with minor, rimmed depressions; containing causer. Epidiaspis leperii

3b Branches with spindle- to club-shaped swellings, bearing: Viscum album

4a Leaf roll and distortion caused by aphids => 6

4b Leaf blade and sometimes young fruits with pocks or felt-like upward archings on underside, caused by gall mites => 5

4c Leaves browned; at high densities vagrant mites may cause russeting Aculops unguiculatus

4d Yellowish spots or blotches apparent on both sides of leaflet, with whitish patches on underside. Microstroma juglandis

5a Pocks, up to 2 mm long, on both sides or only visible on upperside, rotund, if mature, black-brown with irregular cavity. Often many. Also on skins of fruits. Aceria tristriata

5b Similar pocks, protruding at the underside as up to 5 mm high cones Aceria brachytarsus

5c Crook-backed usually upward arching, reticulately striate by thickened venation and often angularly restricted. In depression on underside are whitish erinea consisting of long, cylindrical acuminate hairs. Aceria erinea

6a Loose roll of young leaflets, ± sickle-like distortion of midrib. Aphids on upper side of midrib. Panaphis juglandis

6b Similar roll of leaflets; aphids on leaf underside. Chromaphis juglandicola

Last modified 18.xi.2023