ARS Newslink has posted a report about efforts to stop the spread of water primrose (Ludwigia spp., incl. L. hexapetala) in the U.S. Scientists stationed in the plants' native home of South America are currently working to find biological control options that they hope will keep the plant in check. One reason the water primroses are getting attention is that infestations create patches of standing water in lakes, rivers and streams - that's prime habitat for mosquitos, and a breeding ground for mosquito-borne diseases. You can read more about the water primrose invasion in California in this 2003 ISW post.
Thanks to Sandy L. for posting about the report to the ALIENS-L listserver.