World dissemination of the cereal-cyst nematode (Heterodera avenae) and its potential as a pathogen of wheat.

World distribution of the cereal-cyst nematode is herein reviewed. It is suggested that Heterodera avenae originated in Europe and has been widely disseminated, largely by the activities of Man but also by wind movement of cysts. So far, it may not have spread to some major wheat-growing regions of the New World, but a non-friable soil structure limits population level and disease. Yield loss could result from the introduction of new cultivars to developing countries where H . avenae has not been detected or where existing cultivars possess tolerance.