Data were gathered in 1984 on the distribution, size, and habitat of populations of purple loosestrife in Wisconsin. Lythrum salicaria was found throughout Wisconsin, but most populations were still small and amenable to eradication with spot applications of herbicide. We compared the effectiveness of three dosages of glyphosate herbicide for eradicating small populations of purple loosestrife. High dosage treatments killed a slightly higher percentage of loosestrife than low dosage, but also caused much greater destruction of desirable perennial vegetation. The increased disturbance associated with high dosage, led to a high density of purple loosestrife seedlings in the following year. Low dosages of glyphosate herbicides are, therefore, recommended for control of L salicaria.
Reinartz, J.A., J.W. Popp and M.A. Kuchenreuther. 1987. Purple loosestrife (Lythrum salicaria): Its status in Wisconsin and control methods. Field Station Bulletin 20(1): 25-35.