Alfalfa stem nematode, Ditylenchus dipsaci, belongs to a diverse species of nematode often referred to as stem and bulb nematodes. Within this species are a number of races or strains of the nematode. Alfalfa Stem Nematode is one that attacks and reproduces only on alfalfa (Medicago sativa) and sainfoin (Onobrychis viciifolia) plants. The ASN occurs in all regions of alfalfa production worldwide and can dramatically reduce plant stand and forage yields.