Purple loosestrife (Lythrum salicaria and Lythrum virgatum) is a semi-aquatic, perennial invasive species. This weed often grows 6 to 8 feet tall exhibiting leaves that are simple, entire and opposite or whorled. Rose-purple flowers having 5 to 7 petals are arranged in long vertical spikes. It has been documented that this invasive species has made a steady, westward spread from Massachusetts and has over time infested lands throughout the northeast, midwest and western United States. The latest estimate is that 475,000 acres of wetlands and riparian areas are degraded annually to this pest. Nationwide, losses in excess of $46 million are occurring due to devaluation of freshwater real estate, the reduction of populations of furbearing animals and migratory waterfowl and the destruction of natural habitats for recreational enjoyment.
In 1993, leaf feeding chrysomelids (Galerucella calmariensis) and (Galerucella pusilla) that attack purple loosestrife were released on infestations within the lower stretches of the Missouri River in South Dakota. Since 1994, root-feeding weevils (Hylobius transversovittatus) that attack purple loosestrife roots and seed weevils (Nanophyes spp.) that attack flower buds have been released in addition to the continued release of (Galerucella spp.). These release sites continue to be monitored for effectiveness and for redistribution of populations to new purple loosestrife infestations.
Beginning in 1997, enhanced bioagent rearing and redistribution efforts have fostered an expansion of biological control efforts on large established purple loosestrife infestations on the Missouri, Niobrara and Platte Rivers in South Dakota and Nebraska. The following initiatives are underway through the efforts of the recently formed South Dakota/Nebraska Purple Loosestrife Management Committee:
- Development of a large-scale purple loosestrife biocontrol rearing and redistribution facility in partnership with the Springfield State Prison , Bon Homme County, South Dakota with technical support and oversight provided by the U.S. Fish and Wildlife Service, the Charles Mix County Weed and Pest Board and the South Dakota Department of Agriculture.
- Development of several satellite purple loosestrife biocontrol rearing and redistribution locations throughout the project area that are being managed by local county weed and pest personnel.