have been implicated as potential sources of ground and surface water pollution and attendant health hazards (Nielsen and Lee; Hoar et al.; United States Environmental Protection Agency). These adverse effects have led to imposition of regulatory actions ranging from herbicide restrictions to use quotas. In the United States, atrazine, the most commonly detected herbicide in groundwater, is currently a restricted-use product. In the Netherlands and Denmark, quotas have been imposed to regulate the amount of pesticides that can be used for crop production. The Netherlands aims for 30 percent reduction in herbicides (active ingredient) by 1995 when compared to 1984-1988 use levels. The target reduction by the year 2000 is 45 percent (Wossink and Renkema). Denmark's goal is to reduce current herbicide use levels by 50 percent in 1997 compared to 1987 use levels (Thompson, Stafford, and Miller). In spite of these concerns, the deleterious effects of uncontrolled weed populations are too significant to be ignored (e.g., Auld, Menz, and Tisdell). In the United States alone, the annual value of crop yield losses would run into several billions of dollars if weeds were left unchecked (Chandler, Hamill, and Thomas). These considerations suggest that information that results in the use of profitable and environmentally friendly weed-control strategies is valuable. Several computer-based bioeconomic models that serve as useful decision support tools for crop production management are now available (Mortensen et al.; Swinton and King 1994a, 1994b; Wilkerson, Modena, and Coble; Thornton et al.). These models employ concepts of economic thresholds to recommend control