Noxious weeds are a threat to sustainable crop production intensification. For this reason, crop seeds in general, and certified seeds in particular, should be free of weed propagules. Nearly zero tolerance is the rule for noxious weeds, which are weeds specified by law as being especially undesirable, troublesome and difficult to control.

This manual is a technical support to regional harmonization of seed regulations and provides information to crop protectionists, seed specialists and policy makers on noxious weeds not acceptable in certified seed lots. Noxious weeds in production of certified seeds should be anticipated and avoided in a context where globalization of trade has favored spread of many invasive alien plants, displacing native species and taking land out of production in many countries.