gallers on Zea

1a On above-ground parts => 2

1b Roots with nodular or slender spindle-shaped swellings. Meloidogyne chitwoodi

2a Malformations caused by weakly dusting fungi => 7

2b Malformations caused by animals => 3

3a Malformations mainly on young plants caused by animals developing inside => 6

3b More or less distinct leaf rolls caused by aphids => 4

4a Greenish aphids => 5

4b Aphids glossy dark-brown. Young leaf blades, if weakly infected, slightly rolled and discoloured mainly at base, soon withering. Sipha maydis

5a Adult wingless aphids oblong-oval, 1.75–2.6 mm long, powdered, dark green to bluish black, with very dark, brown-black extremities. Rhopalosiphum maidis

5b Wingless aphids rotund-oval, 1.6–2.4 mm, not powdered, dull olive-green to dark grey-green, with green translucent to brown, at the tip dark-brown extremities. Rhopalosiphum padi

6a Plant excessively leafy. Leaves contorted and disfigured, partially twisted. Shoots stunted, at base spongy, swollen; internodes distinctly shortened and thickened. Ditylenchus dipsaci

6b Shoots of young plants stunted; slightly swollen just above ground; plants additionally leafy; inner leaf destroyed. Leaf sheaths and -blades ± twisted. Usually several yellowish-white maggots at base of shoots, up to 4 mm long, which feed on various plant parts Oscinella frit

6c In addition to frit fly occurring on maize and with similar biology is the closely related: Oscinella pusilla

7a Different plant organs with pea- to even child head size, at first white-grey covered, bulging swellings, which release the previously smeary, then dusty, blackish single smut spores when ripped open. Mycosarcoma maydis

7b The female and also the looser male inflorescences completely or only partially transformed into a unified smut mass, initially enveloped by a whitish to reddish membrane. Diseased flowers sometimes with leaf-like structures. Spores united in balls. Sphacelotheca reiliana

7c Inconspicuous and ephemeric fungal down on the underside of yellowing leaves of seedlings. It consists of erect conidiophores that apically are dichotomously branching several times, each terminal branch ending in a conidium. Peronosclerospora maydis