ABSTRACT
Making Weed Management Decisions. . . . . . . . . . . . . . . . . . . . . . . . . . . 218 12.6 Limitations of Empirical Crop-Weed
Interference Data for Decision Making . . . . . . . . . . . . . . . . . . . . . . . . . . 220 12.6.1 Seeds Produced by Unmanaged Weeds . . . . . . . . . . . . . . . . . . . 220 12.6.2 Effects of Management on
Weed Competitiveness and Seed Production . . . . . . . . . . . . . . . 221 12.6.3 Effects of Multiple Weed Species . . . . . . . . . . . . . . . . . . . . . . . 223 12.6.4 Instability of Crop-Weed Interference Relationships . . . . . . . . 224 12.6.5 Field Scouting to Determine Weed Densities. . . . . . . . . . . . . . . 225 12.6.6 Variation in Spatial Distribution of Weeds. . . . . . . . . . . . . . . . . 226
12.7 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228
Losses in crop yield and quality from the interactions between weeds and crops provide the basis for modern weed management.1 Crop producers have relied upon herbicides since the early 1950s as the primary method for controlling weeds because
they were cheap, convenient, and effective.2 However, public concern about food safety and the environment has caused considerable debate about the impact of herbicides on agroecosystems. Excessive or inappropriate use of herbicides could be avoided if they were applied only when weed control is justified both from the biological and economic perspectives. Thus, the development of decision-support software that farmers, consultants, extension personnel, and other agronomists could use as a part of an integrated weed management (IWM) program is needed.2
