The History and Distribution of Downy Brome (Bromus tectorum) in North America

Downy brome ( Bromus tectorum L. # BROTE) has developed into a severe weed in several agricultural production systems throughout North America, particularly on rangeland and in winter wheat ( Triticum aestivum L.). Several million hectares of winter wheat, pastureland, alfalfa ( Medicago sativa L.), grass seed fields, and overgrazed rangeland, as well as other crops, have been invaded by this annual grass since its introduction into this hemisphere. Downy brome is most abundant in the Great Basin and Columbia Basin areas of the western United States, but is found throughout the continental United States and parts of Canada and Mexico. In some cases, the vegetation on overgrazed rangeland consists totally of downy brome, while winter wheat growers in the western United States proclaim it as their worst weed problem. Changes in tillage practices that are currently being implemented for the control of soil erosion coupled with the lack of selective herbicides for the control of downy brome have aided its increase and spread.