Volunteers and Invasive Plants: Learning and Lending a Hand link

U.S. Fish & Wildlife Service
America's National Wildlife Refuge System

Volunteers and Invasive Plants: Learning and Lending a Hand

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Managing Invasive Plants

Planning and Methods for Managing Invasive Plants


What Is IPM?

What is a Pest?

  • A pest is any organism that interferes with management goals.
  • A pest can be an invasive plant, animal or insect.
  • A pest can also be a native plant, animal or insect if it lives where it is not wanted or causes harm to crops, livestock or management goals.

The US Fish and Wildlife Service (USFWS) takes an Integrated Pest Management (IPM) approach to managing pests such as invasive plants. IPM is a science-based, decision making process that "coordinates the use of pest biology, environmental information, and available technology to prevent unacceptable levels of pest damage by most economical means, while posing the least possible risk to people, property, resources, and the environment."

According to the official definition of the Federal Insecticide, Fungicide, and Rodenticide Act, IPM is sustainable approach to managing pests by combining biological, cultural, physical, and chemical tools in a way that minimizes economic, health, and environmental risks.

IPM can

  • reduce the risk from pests and pest management
  • help managers understand pests and the conditions that favor pests
  • increase use of more effective scientific management of pests
  • increase partnerships, collaboration, and coordination in managing pests
  • increase safer uses of pesticides and other management tools
  • decrease or eliminate unnecessary pesticide use

Read about the policy that guides the Refuge System in using IPM:
Department of the Interior IPM Policy (1 MB PDF)

The IPM Process

The USFWS follows an 11-step process for developing and implementing an IPM strategy. The IPM process involves careful and continual assessment, planning, and monitoring to help managers develop strategies that are effective in achieving and maintaining desirable plant communities while managing invasive plants.

The process involves

  • establishing priorities based on land management goals
  • using prevention, early detection, and rapid response strategies that help prevent invasive plants from becoming a problem
  • surveying, mapping, and monitoring current and potential invasive plants
  • selecting methods based on science and current technology
  • conducting education and outreach efforts that increase invasive plant awareness among the public, volunteers, and refuge staff

Other important components of the IPM process include: understanding an invasive plant’s biology and ecology, as well as factors that affect plant numbers; establishing action thresholds; building partnerships; adhering to applicable laws and regulations; and documenting and evaluating results.

Read more about IPM:
US Fish and Wildlife Service Integrated Pest Management (265 KB PDF)

Comprehensive Conservation Plans and IPM

The first step in the IPM process is understanding land management goals and establishing priorities. In the refuge system, management goals and priorities are determined through the development of a Comprehensive Conservation Plan (CCP). The National Wildlife Refuge System Improvement Act of 1997 requires each refuge to prepare a CCP by 2012. The purpose of the CCP is to guide refuge management decisions over the 15-year life of the plan. A CCP presents wildlife, habitat, and public-use management goals and objectives along with strategies to achieve them. Many CCPs describe strategies to eradicate, control, or contain invasive plants in order to achieve wildlife and habitat management objectives. As part of the IPM process, a CCP might describe the use of volunteers to monitor and control invasive plants on refuge lands and waters.

See which refuges have completed CCPs:
Comprehensive Conservation Plans



Preventing invasive plants from becoming established is much easier, less expensive, less time-consuming, and more effective than trying to control them after they have become widespread.

Elements of invasive plant prevention strategies include

  • limiting the introduction of invasive plant seeds into an area
  • minimizing disturbance of desirable vegetation along roadsides, trails, and waterways
  • managing land to maintain communities of native and desirable plants to compete with invasive plants
  • carefully monitoring high-risk areas such as transportation corridors and disturbed or bare ground
  • revegetating disturbed sites with desirable plants

Read more about prevention:
Invasive Plant Prevention Guidelines (133 KB PDF)

Early Detection and Rapid Response

Even the best prevention efforts will not stop all invasive plant introductions. Early detection and rapid response (EDRR) efforts address invasive plants while infestations are small. Once populations become widely established, they may be very difficult and expensive to control.

Detecting and responding to plant invasions requires a complex series of actions that can be grouped into three main categories:

 Diagram showing the three components of EDRR; early detection, rapid assessment, and rapid response.

EDRR efforts are designed to DETECT new invasive plants in time to allow efficient and environmentally sound ASSESSMENTS to be made; and RESPOND to invasions in an effective, environmentally sound manner that will prevent the spread and permanent establishment of invasive species.

Read more about the EDRR strategy:


Survey and Inventory

In order to develop overall invasive plant management strategies, managers conduct surveys or inventories to gather general information about invasive plants and their environments. Surveys and inventories are used to detect and document the occurrence of invasive plants in an area at one point in time, and can be an essential element in detecting new infestations before they become a bigger problem. The terms survey and inventory are sometimes used interchangeably. Another definition is that an inventory can be a census - a total count of the target plants in an area or it can be a survey - a sample of the plants in an area.

Depending upon management objectives, a variety of information may be collected about one or many invasive plant species. Data collection may be very simple, such as recording the location of the infestation as a labeled point on a map, or may include more detailed information about the size of the infestation, the abundance of invasive plants, and the type of habitat or plant community in which the infestation occurs.

Detector Dog Research
Photo of first slide in detector dogs slide show.

Surveys and inventories are conducted using a variety of methods:

  • Observers may systematically survey an area on foot, recording their findings on a standardized form, a topographic map, or in a handheld electronic device.
  • The use of specially trained weed-detecting dogs to locate new infestations of invasive plants is being researched as a new method.
  • Predictive modeling is used on large refuges to identify areas that are vulnerable to invasion and highly invaded. Refuge staff and volunteers help in checking the accuracy of the models by “ground truthing” areas using GPS devices.
  • In rough terrain or very large management areas, ground-based surveys can be too time consuming or costly. Survey techniques that can be used to cover larger areas in less time have been developed. For example, with the Digital Aerial Sketch Mapping method, observers detect and record invasive plant infestations from an airplane.
  • Remote sensing using aerial photographs, satellite imagery, and multispectral sensors is another important survey tool. Multispectral sensors record visible, infrared, and thermal bands reflected from some invasive plant species. Their locations are saved in digital format and displayed on maps.

    Despite their utility as rapid and cost-effective methods, aerial-based surveys generally do not provide the level of detail and accuracy that ground-based surveys do. Often, the areas surveyed are checked on the ground to verify and collect supplement data.


Typically, data collected during survey activities are used to create visual displays of invasive plant information on maps. Volunteers often play a key role in mapping invasive plants; in fact, many refuge staff depend on volunteers to get their invasive plants mapped.

Why is mapping so important? Knowing where invasive plants are located and the size of the infestation allows managers to plan their control strategy. Additionally, comparing maps before and after a control method is applied can be used to evaluate the method’s effectiveness.

Mapping Using WIMS
Photo of volunteers using WIMS units.
View story

How does mapping work? While there are different mapping programs available, many refuges depend on computer programs such as Refuge Lands Geographic Information System (RLGIS), which was designed especially for the Refuge System, and the Weed Information Management System (WIMS), designed by The Nature Conservancy. Both of these programs function in mapping software called ArcPad.

Both RLGIS and WIMS users take handheld devices into the field to record the location and size of invasive plant infestations. This information can then be downloaded onto a computer to create maps of individual invasive plants or infestations. These maps are then used by managers for making decisions about which invasive plants to control, how to control them, and how to monitor the progress of their control methods.

RLGIS and WIMS keep track of three general types of records:

  1. Weed occurrence (where weeds are located using global positioning system points)
  2. Weed assessment (the size and status of an infestation spacially indicated as a polygon)
  3. Weed management treatment (which plants were treated with which control method)

Read more about WIMS and RLGIS:


Information collected during surveying and mapping may lead to immediate control actions (rapid response), or may warrant collection of more detailed information through monitoring. Monitoring is the collection and analysis of repeated observations or measurements to evaluate changes in condition and progress towards meeting a management objective. Data collection during monitoring is typically more detailed and precise than data collection during surveys and is repeated over time to detect changes or trends.

For example, by recording the number of invasive plant stems that occur in a given area each year managers can determine whether invasive plant numbers are increasing, decreasing, or staying the same. This information can help managers determine if the plant is becoming invasive (increasing plant numbers), at which point they may need to implement management methods. Where invasive plant management is already occurring, the information may help evaluate whether current methods are effective in reducing invasive plant numbers.

Monitoring is used to evaluate

  • status and trends of invasive plant populations (invasiveness)
  • impact of invasive plants on other species and the environment
  • effects of management methods on target invasive plants
  • impact of management methods on non-target species and the environment

What is the difference between survey/Inventory and monitoring?

The distinction between surveying and monitoring can be confusing because both activities may use some of the same methods, such as mapping.

  • Surveys/Inventories gather general information at one point in time.
  • Monitoring involves collecting detailed information in a systematic way on a repeated schedule.

For example, maps created to document the location of invasive plants so that managers can develop overall management strategies are part of a SURVEY/INVENTORY activity because they represent one point in time. If maps of the same area are created each year for several years to detect changes in invasive plant populations, this activity could be considered MONITORING. This type of monitoring can be used as part of an early detection and rapid response strategy when surveys detect new infestations.


Refuge staff who are responsible for managing the valuable natural resources found in refuges must also keep up with the most current research, technology, and scientific knowledge so they can make the best management decisions. Through various partnerships, cooperative projects, and scientific research, refuge staff continually gather and share information about invasive plants and the methods used to control them.

With the IPM approach, management methods are selected by their potential to not only control the target invasive plants, but also to minimize economic, health, and environmental risks posed by the plant or the methods used to control it. To achieve this goal, managers consider a number of factors to decide how, when, where, and whether invasive plant populations are to be controlled.


Photo of bog turtle.
Invasive wetland plants can interfere with land management goals, such as maintaining habitat for the threatened bog turtle. Photo credit: USFWS
Land Management Goals

Refuge managers establish land management goals to protect the unique habitats and natural resources of the area. Examples of land management goals may be to maintain wetland habitat for the bog turtle (Clemmys muhlenbergii), which is Threatened under the Endangered Species Act, or to maintain prairie grasslands that support grazing animals.

The presence of invasive plants in a particular habitat, as well as the methods used to control them, can interfere with land management goals. It is important to select control methods that support rather than conflict with land management goals. For example, invasive wetland plants such as purple loosestrife (Lythrum salicaria) and reed canary grass (Phalaris arundinacea) have greatly altered bog turtle habitat in New Jersey by displacing native, low-growing grasses and decreasing the amount of waterflow through rivulets that the turtle needs for survival. In a cooperative project involving the USFWS, a control method was implemented that uses cattle to graze the invasive plants. This control method supported the goal of maintaining bog turtle habitat by reducing invasive plants in some areas and restoring waterflow through rivulets created by the cattle’s heavy hooves.

Photo of leafy spurge plant and root with buds.
Leafy spurge plants have extensive root systems with buds from which new plants can emerge. Photo credit: S Dewey/Utah State Univ., www.forestryimages.org
Target Plant Characteristics

Selecting an effective control method for an invasive plant requires knowledge of its biology and ecology. By understanding what a plants needs to survive and reproduce, managers can select control methods likely to disrupt the plant’s growth.

Leafy spurge (Euphorbia esula) for example, has extensive, creeping roots, which can make it very difficult to pull out of the soil. Even if most of the plant is pulled, spurge plants can regrow from the part of the roots left behind. Therefore, methods that do not destroy the root, such as cutting or hand pulling, are usually not effective in controlling leafy spurge.

Site Characteristics

Before they begin management activities, managers often assess the management area to characterize the types of plant and animal life present, as well as soil, water, and other resources. These assessments help managers to identify and monitor important resources that may be affected by invasive plants and/or the methods used to control them. In streamside areas, for example, chemical control with some herbicides may degrade water quality if treatments are applied too close to the water’s edge.

The environmental conditions at a site can also be an important factor influencing the effectiveness of a particular management method. For example, some insects used for biocontrol may not survive in areas that are very cool and humid.


The cost of control methods is another important consideration when deciding which method to use. Some methods require substantial labor costs to apply, whereas others require purchasing special equipment, chemicals, or biocontrol insects.

Managers have the difficult task of weighing the dollar cost of applying management methods against the ecological costs of allowing invasive plants to spread. Because the USFWS has a limited budget for invasive plant management, refuge managers must decide which control methods will deliver the greatest benefits.


The idea behind the IPM approach is that combining several types of controls will be more effective at managing invasive plants than using only one type of control. For instance, combining manual pulling, biocontrols, and herbicides may be a better way to manage a certain invasive plant than herbicides alone.The IPM approach involves combining any of the following methods.

Physical methods icon
Physical Methods

Physical techniques for removing invasive plants include pulling plants by hand, using hand tools, mowing, brush-cutting, weed-whacking, and removing plants with machinery such as bulldozers. Physical approaches are most useful when invasive plant populations are small or isolated. Physical methods may be less practical over a large area.

Chemical methods icon
Chemical Methods

Using an herbicide to control invasive or unwanted plants is a chemical method. Herbicides are often very effective at eliminating their target; unfortunately, they may also injure other plants, soil microbes, or insects. Chemical methods are often used when other methods are not effective and where fast results are needed.

Biological methods icon
Biological Methods

Biological control (biocontrol for short) is the use of one organism to control another. Insects and mites are the most common types of organisms used as biocontrols against invasive plants. Biocontrols weaken, but do not eliminate, invasive plants by feeding or living in them. Relative to other methods, biocontrol can be energy-efficient, nonpolluting, and inexpensive, but may take years to be effective. Biocontrols are tested so that they will damage only one specific invasive plant. If not adequately tested before use, biocontrols may attack unintended plants or become invasive themselves.

Prescribed grazing methods icon
Cultural Methods

Two cultural methods that may help with managing invasive plants are prescribed grazing and prescribed burning. Used alone, prescribed grazing is unlikely to totally eradicate unwanted plants, but when used with other methods, it may be useful. Livestock animals such as cattle or sheep can be used to eat invasive plants, till the soil with their hooves, and disperse native seeds. If not used carefully, grazing can also damage the land and promote invasive plants.

Prescribed fire methods icon

Prescribed fire, if used prudently, may help suppress invasive plants and encourage native plants to return to an area. Some plants require fire for germination and have adapted to be dependent on fire. Care must be used because some invasive plants are also adapted to fire (cheatgrass, Bromus tectorum, is an example) and may be encouraged by burning.

Revegetation icon

Revegetation may be needed after treatment with the methods above if desired plants are not present at the site. If the invasive plant infestation is small, there may be native plants nearby or seeds in the soil that will germinate and fill the spaces left open by the suppressed invasive plants.

However, if there are not native plants or seeds nearby, desirable plants will need to be planted to prevent invasives from returning to the area. It is important that the revegetated plants are able to compete with the invasive plants, as it is likely that there will be invasive plant seeds around for a while.

Management Methods
in Action
Photo of  first slide in the management methods slide show.


Raising the level of invasive plant awareness and understanding among the public and refuge staff is an important component of the IPM process. When refuge visitors understand the problems associated with invasive plants, they are more likely to take the steps needed to prevent their spread.

Volunteers play an important role in educating the public about invasive plant problems on their local refuges. There are also many state and national campaigns to raise awareness and generate action on invasive plants. For example, Stop Aquatic Hitchhikers! seeks to raise awareness about the problem of aquatic nuisance species and provide people with resources to take action.

Read more:
Stop Aquatic Hitchhikers!