Himalayan Knotweed Treatment Project

Himalayan Knotweed Treatment Project

Remove a Himalayan knotweed (Persicarla wallichii) infestation at 5 sites totaling .25 acres in Trinidad State Beach and Patrick's Point State Park to protect the parks from this highly invasive plant. All viable manual eradication methods have been previously used, but have not been successful. Implementation of an Integrated Pest Management strategy is necessary to prevent the plant from spreading further into the two State Parks it is currently found in. Work will: Apply Glyphosate (Rodeo) at a 2% to 5% solution or Imazapyr (Habitat) at a 1% solution with 0.25% surfactant, consistent with the manufacturer's application guidelines, to knotweed, using foliar application techniques; Add an EPA-approved blue marker dye to the solution to track which plants have been treated; Apply no more than 7 oz. of herbicide in the first year, with decreasing amounts each following year; Apply herbicide no more than twice a year; once in the early summer and once in early fall; Apply herbicide for up to 5 years, or until the infestation is eradicated; Follow Best Management Practices (BMP) for herbicide application and handling at all times; Manually remove knotweed to aid in eradication; Dispose of knotweed by recommended methods to ensure knotweed is not inadvertently spread, and; Plant the treated areas upslope of Mill Creek, in Trinidad State Beach, with native seed at a time that will ensure seed germination and a high chance of plant survival. Include plants of varied rooting depths in the seed mix.

Trinidad

Humboldt