. The Canadian field-naturalist. Natural history. 102 The Canadian Field-Naturalist* Vol. 117. Western Region Central Region Eastern Region Figure 1. Dots indicate the 492 known Purple Loosestrife infestations in southern Manitoba as of the fall of 2001 Numerous infestations are found in the Netley-Libau Marsh, in the city of Winnipeg, and Cypress River area. between 1991 and 2001 (10-year period). Central Manitoba, which includes the Netley-Libau Marsh, accounted for 4324 ha () of Purple Loosestrife. The Netley-Libau Marsh (a candidate Manitoba Heritage Marsh and Canadian Important Bird


. The Canadian field-naturalist. Natural history. 102 The Canadian Field-Naturalist* Vol. 117. Western Region Central Region Eastern Region Figure 1. Dots indicate the 492 known Purple Loosestrife infestations in southern Manitoba as of the fall of 2001 Numerous infestations are found in the Netley-Libau Marsh, in the city of Winnipeg, and Cypress River area. between 1991 and 2001 (10-year period). Central Manitoba, which includes the Netley-Libau Marsh, accounted for 4324 ha () of Purple Loosestrife. The Netley-Libau Marsh (a candidate Manitoba Heritage Marsh and Canadian Important Bird Area) accounted for the majority of Purple Loosestrife in the central region while the Assiniboine River accounted for the majority of Purple Loosestrife infestations within the city of Winnipeg. The size of Purple Loosestrife infestations ranged from one plant to thousands of plants. The largest single infestations were found along the Winnipeg River near Great Falls, along the Assiniboine River within the city of Winnipeg, in the Netley-Libau Marsh, and on private land off Main Street in West. St. Paul. Sites in Manitoba with infestations of over 1000 plants represented under 9% of the total num- ber of sites while over 50% of the infestations had under 100 plants (Table 2). The potential to control these smaller populations of under 100 plants with an aggressive weed control program is high. This suggests that there is opportunity to control or eradi- cate over 50% of the Purple Loosestrife infestations presently found in Manitoba. The Manitoba Weed Supervisors Association (MWSA) provided Purple Loosestrife distributional maps for weed districts with Purple Loosestrife infestations. The MWSA represents 34 weed control districts in Manitoba composed of about 70 munici- pal corporations. Of the 34 weed districts in Manitoba, 16 were found to have at least one Purple Loosestrife infestation (Table 3). Three additional districts (Roland, Grey and Woodlands) to which the MWSA pro


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