Meloidogyne hapla Chitwood (northern root-knot nematode)

Meloidogyne hapla is the most common species in the northern U.S., and thus the common name, but it is actually cosmopolitan (CABI/EPPO, 2002). It was first reported as a parasite of hemp by Norton (1966), who found a moderate gall rating of 1.9 (0–4 scale) on seed-grown plants of unreported provenance. Root galling and egg mass production of M. hapla on 123 hemp accessions varied widely (Meijer, 1993); in particular, fiber accessions differed significantly in degree of infection and reproduction. Kotcon et al. (2018) found root galling on five industrial hemp cultivars (‘Canda’, ‘Delores’, ‘Fedora’, ‘Felina 32’, ‘Futura 75’) in a greenhouse experiment. Galling was higher on ‘Felina 32’ than on the other four cultivars, but reproduction did not differ.