Purple loosestrife lacks natural enemies in the United States. Once established, it can destroy marshes and wet prairies and choke waterways. As such, the sale in Missouri of purple loosestrife or any of its hybrids is prohibited. It is also unlawful to distribute or plant seeds, plants or plant parts in the state. Control Recommendations Current mechanical and chemical control methods have only limited success.
Smaller infestations are more likely to be controllable, therefore early diagnosis is critical.
Biological control of purple loosestrife is being studied by Dr. Richard Malecki of the New York Cooperative Wildlife Research Unit at Cornell University. Three beetles, two leaf-eaters and a root miner, that are natural predators of purple loosestrife in Europe have been approved for release in the U.S. after extensive testing. Initial releases will probably take place in Minnesota and Washington. These insects were selected for their specificity to purple loosestrife as a host plant. Do not pull after flowering because this will scatter seed.