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Institute for Wetland and Waterfowl Research, Ducks Unlimited, Stonewall, P.O. Box 1160, Oak Hammock Marsh, MB, R0C 2Z0 Canada; DowElanco Canada Inc., 375 Exmouth Street, Sarnia, ON, N7T 5N8 Canada; Institute for Wetland and Waterfowl Research, Ducks Unlimited, Stonewall, P.O. Box 1160, Oak Hammock Marsh, MB, R0C 2Z0 Canada; Ducks Unlimited Canada, 1365 Midland Avenue, Kingston, ON, K7L 4V2 Canada

This study examined the effects of the herbicide triclopyr amine on purple loosestrife (Lythrum salicaria) and non-target vegetation in a southern Ontario wetland during 1991 and 1992. Herbicide treatments were applied ("spray-to-wet" technique) during bud-to-early bloom stage at 0.5, 1.0, 1.5% concentration of active ingredient. During 1991, all treatment levels effectively controlled the above-ground portion of purple loosestrife. Native plants were minimally affected at most treatment levels. During 1992, adult purple loosestrife was not present in the highest treatment indicating that triclopyr amine effectively eliminated the root system. Loosestrife seedling numbers were higher in the 1.0 and 1.5% treatment plots. Sedge (Carex spp.), rice cut grass (Leersia oryzoides) and beggar ticks (Bidens sp.) increased above 1991 levels. Removal of adult purple loosestrife allowed more light to reach the substrate surface and created favorable conditions for seed germination and plant growth. At 1.5% solution, triclopyr amine effectively controlled adult purple loosestrife and had a neutral or positive effect on the abundance of native plant species.