Integrated Pest Management

Integrated pest management uses a combination of mechanical or physical, biological, and chemical pest control methods selected to optimize control efficacy while minimizing associated risks to human health, property, and the environment. Statewide, purple loosestrife can be considered in the early phase of invasion in Montana. Management strategies most appropriate for early phase invasions are prevention, early detection and rapid response, and containment, and should be applied according to local purple loosestrife population characteristics.

In riparian/wetland areas not infested with purple loosestrife, regular surveys (every three years) for new purple loosestrife populations should be planned. An early inspection should be made before or at early flowering, to initiate control before seeds set and have an opportunity to disperse. Individual plants should be considered high-priority targets for eradication programs. Records of plant densities and GPS location should be maintained and updated at each inspection. In addition, horticultural plantings of purple loosestrife should be replaced with non-invasive species.

Individual plants and populations detected along irrigation ditch banks should be prioritized for eradication using spot spray treatments (follow label instructions regarding restrictions for herbicide application on active irrigation ditches). Large-scale populations should be contained by early detection and eradication of satellite populations, and containment of the parent population using herbicidal control along its borders. One study suggests integrating herbicidal control with G. calmariensis is more effective at suppressing purple loosestrife populations than either treatment applied alone. Biological control insects should be established in the center of large-scale populations where herbicides are not sprayed. Over time, large-scale populations can then be reduced by herbicide applications from the edges to the center. Insects established in the center of the population will reduce seedling re-establishment where herbicides have been sprayed.

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Last Modified: 08/12/2008