Japanese Knotweed is an herbaceous perennial native to Eastern Asia. It can grow in a wide variety of habitats and is insect-pollinated. In the US, it spreads mainly through large rhizomes and these can float down rivers and quickly spread.
The Hokkaido and Kyushu biotypes of the insect Aphalara itadori were chosen as potential biological control organisms. The insects are expected to reduce the severity of infestations of Japanese, Giant, and Bohemian knotweed, and are known to be highly host-specific due to their intimate relationship with their host plants.
Multiple years of mowing and herbicide treatment can keep the infestation at a manageable level but may not be enough to destroy the plants, according to Penn State Extension.
The USDA has completed an environmental assessment and the knotweed psyllid is now available for release. This insect has already been released in both Canada and the United Kingdom. More information is available from the Federal Register – Animal and Plant Health Inspection Services