‘Shape-shifting’ primrose plant plagues coastal states
While the best and most appropriate control methods can vary widely depending on where Ludwigia is found, Grewell says some of the best successes have involved the use of broad-spectrum herbicides as part of an integrated (multifaceted) weed control strategy. The U.S. Environmental Protection Agency has approved several herbicides for use in these delicate aquatic environments.
That’s the approach Grewell recommended to the city of Eugene, Oregon, where Ludwigia has infested the Delta Ponds, a 150-acre waterway that was once a side-channel of the Willamette River. The weed must be totally eradicated to support a fish habitat restoration project that will reconnect Delta Ponds to the river. Grewell and her colleagues suggested the use of herbicides to reduce the dense weed mass. As the area Ludwigia covers is reduced and its seed bank is depleted, the emphasis will shift to manual control.
The most important step of all, Grewell says, is continued vigilance. “Prevention of a new invasion is the best management strategy,” she says. “As new plants emerge or spread from an established site, you really have to control them. Contact area Extension agents right away if you think you’ve spotted an infestation.”
For more information on ludwigia and some of the research projects underway, click here.