Curbing Invasive Plants in the U.S.: Prevention, Eradication and (at Last Resort) Control.

Curbing the entry and spread of plants that are Invasive Alien Species (IAS) has been a goal in the U.S. for centuries.  This prolonged endeavor has yielded decidedly mixed results.  Most cost effective has been the prevention of entry by species that are known (or likely to become) IAS.  Inspecting in-coming cargo adequately for these species is logistically and financially daunting and can invoke concern as an impediment to international trade.  Limitations of prevention systems include frequent ignorance of how a non-native species will perform in a new range, especially when little or nothing is known about its ecology.  No inspection/quarantine system will prevent all hazardous species from being transported beyond ports.  As a result, a second line of defense, now termed Early Detection/Rapid Response (ED/RR) has gained much deserved support.  Under ED/RR best practices frequent surveys are conducted beyond the ports for populations of newly arrived species.  If a species is judged invasive, a Rapid Response applies whatever tools are most effective to eradicate - totally destroy - the immigrant population(s).  Often years elapse however before an introduced species is detected in a new range.  Consequently, its eradication may be prohibitively expensive.  Control, i.e., checking population growth and spread, is usually considered the best remaining option.  But control incurs chronic costs and may be for naught through any lapse in its application.  The future of combating the growing list of IAS will be determined by the amount of uninterrupted effort that will be applied for prevention, eradication and, as a last resort, control of these highly destructive species.