Evaluation of an integrated management approach for the control of purple loosestrife, Lythrum salicaria L., in southern Manitoba, biological control and herbicides

Abstract

Purple loosestrife ('Lythrum salicaria' L.) is a European wetland perennial that was introduced to North America in the early 1800s. It forms large monodominant stands that are thought to adversely affect ecosystem dynamics wherever it occurs. Field cage experiments were conducted in a 2 ha stand of purple loosestrife at Netley-Libau marsh in southern Manitoba from 1996 to 1998 to evaluate the effectiveness of an Integrated Vegetation Management (IVM) strategy using single techniques (herbicides (glyphosate and triclopyramine) and classical biological control ('Galerucella calmariensis' L.)) and combinations of techniques (herbicides combined with classical biological control). Results of this study indicate that herbicides and classical biological control are compatible strategies for purple loosestrife management. Triclopyr amine would be effective in areas where native vegetation still persists while glyphosate may be effective for purple loosestrife control in areas where monospecific stands of adult purple loosestrife dominate. Based upon the results of this study, it is best to treat an area infested with purple loosestrife with a herbicide, leaving areas of refugia for biocontrol agents. Release of 'G. calmariensis' can be done at about the same time herbicides are applied or the year after herbicides are applied. (Abstract shortened by UMI.)