gallers on Viburnum

1a On parts above ground => 3

1b On root collar or on roots => 2

2a On stem base gall-like, clumpy accumulation of stubby, succulent, swollen, ± branched and broadened shoots. “Leafy gall”. V. opulus: Rhodococcus fascians

2b Roots with nodular to spindle-shaped swellings. Viburnum spp.: Meloidogyne hapla

3a On flowers => 13

3b On axial parts of shoots, shoot tips or leaves => 4

4a On shoot tips and leaves => 6

4b On axial parts of shoots => 5

5a Pencil- to finger-thick twigs bear on several nodes globular to spindle-shaped swellings, up to 20 (33) mm thick, at first succulent, soon woody, slightly longitudinally grooved on their surface, which extends more than halfway around the axis. V. opulus: Agrobacterium tumefaciens

5b Thinner axial parts with rimmed depressions containing causer under pear-shaped scales up to 3 mm long. V. lantana, opulus: Chionaspis salicis

6a Malformations of indefinite shape, mainly on several terminal leaves => 9

6b Leaves with localised galls, ± constant in shape or with ± expanded pubescence => 7

7a Galls lenticular or spherical => 8

7b Underside of leaves with dense, abnormal pubescence on ± expanded rotund spots. Hairs ± stalked, star-shaped, slightly larger and more rigid than normal ones. V. lantana: Unidentified gall mite

7c Clusters of hairs causing depressions in vein axils. V. tinus: Unidentified gall mite

8a Pouch galls protruding on upperside, usually many, short-stalked, pinhead-shaped; sometimes ± reddened, covered with rigid hairs. With a strongly pubescent exit hole on underside. V. carlesii, lantana, rhytidophyllum: Eriophyes viburni

8b Leaf blades often with many parenchyma galls, up to 6 mm broad, rotund, flat on both sides often ± reddened on upperside, pale green on underside. Each containing a single orange-yellow larva. V. lantana, maculatum: Sackenomyia reaumurii

9a Malformations of many leaves on often conspicuously shortened shoot tips of younger or older bushes; caused by aphids => 10

9b Leaf blades of young plants or older bushes or basal shoots at infestation site deflected, especially over the tip; leaf blade curled and locally deep green. Viburnum spp.: Philaenus spumarius

10a Malformations on V. opulus and several cultivated species, rarely on V. lantana => 11

10b Malformations only on V. lantana. Leaf margin loosely rolled. Aphid olive-yellow to –green, with broad transverse brown-black bands: Aphis lantanae

11a Leaves strongly curved or curled => 12

11b Leaves usually slightly curled and slightly rolled inwards at margin. Galls only in spring. V. opulus and several cultivated species: Aphis fabae

12a Malformations inhabited throughout the year. V. opulus, lantana and many cultivated species. V. carlesii, cotinifolium, dilatatum, lantana, opulus, rhytidophyllum, tinus: Aphis viburni

12b Similar malformations, but only inhabited in spring. V. lantana, opulus: Ceruraphis eriophori

13a Flowers swollen, unopened, often partially reddened. Corolla thickened, slightly leathery. Stamens partially aborted. Ovary ± swollen. Containing yellow, jumping larvae. V. lantana, opulus: Contarinia lonicerearum

13b Similar flower galls with 2–3 white to sulphur-yellow jumping larvae. V. lantana, opulus, tinus: Contarinia viburnorum