Biological Control Initiative for Invasive Knotweeds in North Carolina

Knotweeds within the old-world Reynoutria (syn. Fallopia) species complex, native to China and Japan, were once planted widely for their ornamental value and for erosion control.  They have since escaped cultivation and are now invasive throughout parts of Europe, Australia, New Zealand, Canada, and the United States, including North Carolina.  A North American Knotweed biological control working group with cooperators from the United States and Canada was organized to assess the suitability of proposed biocontrol organisms.  The Knotweed Psyllid, Aphalara itadori, was recently approved for distribution and release for this purpose, and pilot releases began in the U.S. in 2020 on populations of Japanese knotweed (Reynoutria japonica = Fallopia japonica), giant knotweed (R. sachalinensis = F. sachalinensis), and their hybrid Bohemian knotweed (R. ×bohemica = F. ×bohemica).  In cooperation with diverse stakeholders, field releases of two biotypes of A. itadori have been conducted in three ecoregions of North Carolina.  Observations on establishment and overwintering capability in North Carolina will be discussed.