Abstract
The most common nematodes on onion in Idaho and eastern Oregon are root-lesion nematodes (Pratylenchusspp.), root-knot nematode (Meloidognye hapla), stem nematode (Ditylenchus dipsaci) and stubby-root nematodes (Paratrichodorusspp. andTrichodorusspp.). This publication details their distribution and host range, biology and life cycle, plant symptoms, impact on yield and management. 12 color photos.