Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)

Department / School


First Advisor

W. E. Arnold


Downy brome (Bromus tectorum L.) is a severe weed problem in winter wheat (Triticum aestivum L.) throughout North America. Downy brome competes for space, light, nutrients in the soil, and most importantly moisture. Rydrych reported that a grower with reasonable control of downy brome can increase yield of winter wheat 6-12 bushels per acre. The lack of selective herbicides which control downy brome in winter wheat and conservation tillage practices have contributed to the spread of downy brome. Some herbicides labeled for downy brome control in winter wheat require incorporation. Incorporation of herbicides may not be compatible with reduced or no-tillage planting systems-which have been implemented to prevent soil erosion and winter kill of wheat. Metribuzin [4-amino-6-(1,1-dimethylethyl)-3(methylthio)-1,2,4-triazine-5(4H)-one] controls downy brome in winter wheat in the Pacific Northwest and the lower Great Plains regions. However, metribuzin is not used in South Dakota because of crop injury and inconsistent control. Metribuzin applied before the wheat develops secondary roots can accentuate winter kill. Freezing conditions or snow cover may inhibit the application of metribuzin at the proper growth stage of winter wheat. BAY-SMY-1500 (4-amino-6-(1,1-dimethylethyl)-3ethylthio)-1,2,4-triazine-5(4H)-one] is a herbicide which selectively controls downy brome in winter wheat. BAY-SMY1500 can be applied to a wider range of wheat growth stages without injury which may be associated with metribuzin. The objectives of these studies were to evaluate combinations of BAY-SMY-1500 and metribuzin for synergistic interactions and for downy brome control in winter wheat. Additionally, the tolerance of five cultivars of winter wheat to BAY-SMY-1500, metribuzin, and combinations of these herbicides was examined.

Library of Congress Subject Headings

Wheat -- Weed control






Number of Pages



South Dakota State University