Dichotomous table for gallers on Amaranthus
by Hans Roskam
1a On above ground organs, sometimes encroaching onto upper part of main root => 2
1b Side roots with nodular or spindle-shaped swellings. Amaranthus spp.: Meloidogyne hapla
= The cyst-developing eelworm Heterodera schachtii has been recorded on several Amaranthus species
2a On stems or leaves => 3
2b Flowers of single panicles ± enlarged, thickened and reddened. Bracts cylindrically thickened, rolled, inflated, wrinkled. A. retroflexus: Inducer unknown; possibly galls with oospores of Wilsoniana bliti.
3a Shoot tips ± stunted. Leaves ± clustered, margins deflected, sometimes contacting; leaf blades arched upwards, ± curled and partially discoloured. Amaranthus spp.: Aphis fabae
3b Axial parts, sometimes also flower parts, variously swollen, also ± distorted. Inside tissue is a mycelium which develops oospores. Mature oospores dark brown-red to blackish translucent. Amaranthus spp.: Wilsoniana bliti