Orobanche crenata is a parasitic weed that causes severe yield losses in important grain and forage legume crops. Cereals have been reported to inhibit O. crenata parasitism when grown intercropped with susceptible legumes, but the responsible metabolite has not been identified. A number of metabolites have been reported in cereals having allelopathic properties against weeds, pests and pathogens. We tested the effect on O. crenata seed germination and radicle development of several allelochemicals identified in cereals. We found that 2-benzoxazolinone, its halogen acetylated derivative 6-chloroacetyl-2-benzoxazolinone, and scopoletin significantly inhibited O. crenata seed germination. Benzoxazolinones, L-tryptophan and coumalic acid caused the stronger inhibition of radicle growth. Also other metabolites reduced radicle length being this inhibition doses-dependent. Only scopoletin caused cell necrotic-like darkening in the young radicles. Prospects for their application to parasitic weed management are discussed.