The Oregon Invasive Species Council updates the 100 Worst List annually. To be added to Oregon’s 100 Worst List of invasive species, the invader must be non-native to Oregon and absent from the state or limited to a small, contained range within the state; and pose a greater threat than something already listed.

In creating this list, the Oregon Invasive Species Council weighs factors such as:

  • the risk to human health 
  • the impact of the species in habitats similar to those found in Oregon
  • the likeliness of the species to cause significant economic loss
  • the difficulty other regions have had eradicating the invader
  • the capacity for the species to spread in Oregon

2015 Oregon Invasive Species Council's 100 Worst List (pdf)

2014 Oregon Invasive Species Council's 100 Worst List  (pdf)