Section 2. Integrated Invasive Plant Management and the Role of Herbicides

 
Photo courtesy: Becky Kington, Montana Weed Control Association

Photo courtesy: Becky Kington, Montana Weed Control Association

The spread of invasive plants is often considered analogous with a biological wildfire. As with wildfire management, a variety of techniques are available for management of invasive plants. These include prevention, early detection, timely control and site rehabilitation.

A successful long-term management program should be designed to include combinations of prevention and cultural, biological, mechanical, and herbicide management methods. This is particularly true in restoration programs where seedling establishment is dependent upon suppression of competitive species. 

Developing and Implementing an Integrated Invasive Plant Management Strategy

The goal of any management plan should not be to just manage the invasive plant but to improve the desirable plant community and prevent reinvasion or invasion by other undesirable plants. Containing existing populations, restoring natural areas severely degraded by invasive plants, and preventing the establishment of invasive plants in non-infested lands is critical for maintaining the ecological health and economic integrity of rangeland and natural areas. This can be achieved by identifying management options that will promote a healthy, weed-resistant plant community that consists of diverse groups of species that occupy most of the niches. 

Following are some guidelines and considerations for developing an invasive plant management strategy:

  • Identify the goal(s) you want to achieve (e.g. enhance forage quantity and quality, restore native vegetation, improve wildlife habitat).
  • Identify desired management outcomes that can be measured with long-term monitoring. For example, a desired outcome of “reduce spotted knapweed density by 95% over 5 years” can be measured. 
  • Identify and accurately delineate lands infested with invasive plants. Knowing the location and extent of infestation can determine the control/management method used, assist in prioritizing management strategies, and identify areas where eradication, containment or control can be achieved.
  • Gain a thorough understanding of the biology and ecology of the invasive weed(s) you are managing including susceptible habitat, spread vectors, etc.
  • Identify management constraints (environmental, financial, technological, social, and operational). 
  • Review effectiveness of each management method on the target plant including mechanical, cultural, biological, and herbicide methods and integrate management techniques that will optimize control. 
  • Prioritize sites where treatments will most effectively contain and control the infestation.
  • Coordinate effort among interested parties
  • Be flexible: Use long-term monitoring and evaluation to identify strengths and weaknesses in your strategies and methods. Adapt management approaches to improve effectiveness and prevent reinvading populations from becoming established. 
  • Establish an annual follow-up treatment program to prevent re-infestation (e.g., spot treatments, modifying livestock grazing, burning, etc.)
  • Plan for a long-term commitment to your management program. Many invasive plants have seed that remains viable in the soil for eight years or more, so long-term monitoring and follow-up management will be necessary for successful control.

References:

DiTomaso, JM. 2000. Invasive weeds in rangelands: Species, impacts, and management. Weed Science, 48:255-265.

Duncan, CA and JK Clark eds. 2005. Invasive Plants of Range and Wildlands and Their Environmental, Economic and Societal Impacts. Weed Science Society of America.

Sheley, RL and JK Petroff (eds.) 1999. Biology and Management of Noxious Rangeland Weeds. Oregon State Univ. Press.