gallers on Carpinus

1a On above-ground parts => 2

1b Root with nodule-shaped swellings. C. betulus: Meloidogyne hapla

2a On leaves or buds, also on fruit wings => 5

2b On stems or branches => 3

3a Conspicuously protruding from the bark => 4

3b Bark initially with closed, irregular crooked proliferations, bursting open later on, displaying the woody part surrounded by variously shaped cancers. “Nectria-cancer”. C. betulus: Neonectria ditissima

4a Localised thickenings and sometimes distortion of branches or stems. C. betulus: Viscum album

4b Heavier branches or stems with bushy, up to 1 m large witches’ brooms, with thickened and densely foliate branched axial parts. Leaf blades curled; asci on the undersides June-August. C. betulus, orientalis: Taphrina carpini

5a On leaves and occasionally on the envelope of the fruit => 7

5b On buds => 6

6a Buds swollen, not opening; spherical or egg-shaped, partially pea-size swollen. Scales grey-white pubescent. C. betulus: Unidentified gall mite

6b Buds swollen, enlarged, not developing. Contain yellow larvae. C. betulus: Contarinia trotteri

7a Galls on the leaf blades or in the vein axils of unfolded leaves => 11

7b Swelling of the veins or leaf blade heavily folded or curled => 8

7c Leaves browning. C. betulus: Aculus betuli

8a Venation involved in the malformations => 9

8b Leaf blade between two side veins with a somewhat thickened, pod-like, ± yellowish or usually red upward fold; on the underside a furrow which opens at maturity. Contains several white larvae. C. betulus, orientalis: Contarinia carpini

8c Occasionally also observed in galls of Contarinia carpini are the yellow larvae of Aschistonyx carpinicolus

9a Venation with conspicuous thickenings => 10

9b Side veins and the neighbouring, upward folded parts of the leaf blade conspicuously ± zigzag-like bent in- and outwards. Heavily infected leaf blades ± rolled upwards. C. betulus, orientalis: Aculops macrotrichus

10a Leaves folded upward over the uniform, only slightly thickened midrib. Infestation often extending into the base of the also slightly thickened side veins, sometimes only locally, the neighbouring leaf blade parts fold subsequently. Midrib of early affected leaves usually bent downwards. On the upper side, especially on the midrib, a single- or several yellowish larvae. C. betulus, orientalis: Aschistonyx carpinicolus

10b Midrib and the adjacent parts of the side veins on the leaf underside with conspicuous, interrupted or continuous, in that case bumpy swellings. Leaf blade sometimes over the midrib ± bent upwards. Galls with a double row of chambers on both sides of the midrib. In each chamber, situated between two side veins, a single yellowish-white larva. C. betulus: Zygiobia carpini

11a Malformations without particular connection with the venation => 12

11b Leaf blade in the vein axils at the upper side weakly arched, sometimes discoloured ± purple-red; with corresponding depressions, at their margin conspicuous very long twisted hairs, on the underside. C. betulus, orientalis: Aceria tenella

= Putative inquiline: Phyllocoptes compressus

12a Leaf blade with small, rotund, hardly arched, pale green or yellowish parenchyma galls, up to 4 mm wide. Containing one single yellow larva. C. betulus: Dasineura ruebsaameni

12b Underside of leaf blade with erinea. C. betulus, orientalis: Cecidophyopsis vermiformis