Table 1. Spread of leafy spurge in North Dakota, USA. Year Time (yr) Infested area (ha) 1909 0‡ 0 1962 53 80900.00 1973 64 171400.00 1982 73 348800.00 1987 78 404685.64 1990 81 526091.33 Note: Data were obtained from Leistritz et al. (1992), Lym et al. (1993), Leitch et al. (1994), and Bangsund et al. (1997). ‡Time since leafy spurge is thought to have entered North Dakota rangeland.