Managing Invasive Plants

Planning and Methods for Managing Invasive Plants

INTRODUCTION TO INTEGRATED PEST MANAGEMENT

What Is IPM?

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. Each refuge in the National Wildlife Refuge System is developing a document called a "Comprehensive Conservation Plan" (CCP) by 2012 to guide management decisions. Many refuges have completed the CCP already and many more are in the process. As part of the CCP, managers may develop an IPM or vegetation management plan. These plans identify invasive plant management objectives and the methods refuges will use to achieve them based on the refuge’s land management goals and priorities.

See which refuges have completed CCPs:
Comprehensive Conservation Plans

PREVENTING INVASIVE PLANTS FROM BECOMING A PROBLEM

Prevention

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:

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:

General Guidelines for Establishment and Evaluation of Invasive Species EDRR Systems (432 KB PDF)

A National Early Detection and Rapid Response System for Invasive Plants in the United States (3.4 MB PDF)

COLLECTING INFORMATION ON INVASIVE PLANTS

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.

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.

Mapping

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.

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:

The Nature Conservancy Weed Information Mapping System

NWR Volunteer Weed Mapping Manual (3.3 MB PDF)

Monitoring

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.

SELECTING INVASIVE PLANT MANAGEMENT METHODS

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.

Considerations

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.

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.

Cost

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.

Methods

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.

CONDUCTING AWARENESS AND EDUCATION EFFORTS

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!