Dichotomous table for gallers on Dahlia pinnata
by Hans Roskam
1a Leaf blades arched and curled, caused by aphids or cercopids => 3
1b On root collar or roots => 2
2a Roots with small nodule-shaped swellings. Meloidogyne hapla
2b Conspicuous succulent, cauliflower-shaped proliferations on tubers, on root collar or stem base. Agrobacterium tumefaciens
2c Irregular proliferations of the stem base, combined with an abundant development of buds. Rhodococcus fascians
2d Extensive malformations usually accompanied by R. fascians. Aphelenchoides fragariae
3a Deformities caused by aphids => 4
3b nfected young shoots severely stunted, the leaves curved downwards, curled, dark green close to the froth-covered nymph. Philaenus spumarius
4a Aphid black. Aphis fabae
4b Aphid green. Aulacorthum solani