Relative emergence sequence for weeds of corn and soybeans

Weed emergence timing: a new tool for managing weeds in crop fi elds The success of integrated weed management relies on matching control strategies to the specifi c weed problem in a fi eld. Managers must know not only which weed species (and how many) are present in a fi eld; they also must understand the distribution and development stages of these weeds throughout the fi eld. Weed control recommendations typically provide information on appropriate tillage methods and herbicide selection. But the weed infestation information on which these recommendations are based typically is not suffi ciently detailed to make the best use of these strategies. Information on weed populations can be improved by increasing the time spent scouting fi elds. However, time is a constraint during the busy spring crop season. With an improved understanding of how environmental infl uences affect weed emergence and growth, growers and consultants could better predict when best to invest time in scouting. Better information on weed development and populations could help growers determine the optimum time for tillage and crop planting to reduce weed populations, maximize the effectiveness of mechanical weed control operations, and strategically time burndown and postemergence herbicide applications. Although considerable research and modeling of weed emergence has been conducted in recent years, little effort has been directed toward developing emergence information for the individuals most directly involved in weed management. This publication describes how weed emergence timing infl uences weed management systems. Included are preliminary rankings of relative emergence for important weed species in the Midwest. The Leopold Center for Sustainable Agriculture is supporting efforts to develop more precise ways to predict emergence that will aid the development of more effi cient weed management systems. Sustainable Agriculture