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U.S. Department of Transportation U.S. Department of Transportation Icon United States Department of Transportation United States Department of Transportation

Public Roads - July/August 2010

July/August 2010
Issue No:
Vol. 74 No. 1
Publication Number:
Table of Contents

Are We Winning or Losing the War on Weeds?

by Mary Ann Rondinella and Bonnie L. Harper-Lore

The attack of invasive plants on the Nation's roadsides is still ongoing, but emerging alliances and their successful strategies are on the counterattack.

Facing constrained budgets, DOTs have reduced mowing and spraying applications, allowing aggressive weed species such as this spotted knapweed to flourish in some areas.

On the day you read this article, another 4,600 acres (1,863 hectares) of public lands will be invaded by weeds, according to a Bureau of Land Management and Utah State University estimate. In addition, since the September/October 2002 publication of a Public Roads article on the "war on weeds," a number of new species have spread along the Nation's roadsides. Among the new invaders are cogongrass, Japanese stiltgrass, wavyleaf basketgrass, and Chinese silvergrass.

Research shows that weedy species along roads are directly correlated to plant invasions of adjacent lands. Invasions of weeds degrade habitat, threaten diversity, replace rare native plants, increase erosion, facilitate wildfires, and usurp water resources. The consequences of a failure to win the war on weeds include fewer songbirds, more ranchers out of business, fewer pollinators, lower food production, less wildlife habitat, more loss of recreation, loss of flood control, and loss of water in the West.

Typically, weedy grasses and shrubs go unnoticed by the traveling public. Even for vegetation managers, weeds often are difficult to differentiate from native or other beneficial plants. Without public awareness and increased training for managers, the ecological and economic losses will continue to escalate. In 2004, the impact of invasive species in the United States was estimated at $142 billion per year.

Moreover, although the overall effects of climate change are uncertain, longer growing seasons and more severe droughts could exacerbate the spread and persistence of some weed infestations. For example, a Pennsylvania Climate Impact Assessment published by the Pennsylvania Department of Environmental Protection notes that warmer temperatures may increase the persistence of invasive plants previously killed by cold winters. Kudzu, intentionally planted as an ornamental, formerly was believed unable to survive Pennsylvania winters. But now kudzu stands are in fact persisting, although not expanding. Pennsylvania has begun an eradication program.

In the face of a changing environment and uncertainties associated with that change, the national strategy of early detection and rapid response is still the best overall approach to combat invasive species. State departments of transportation (DOTs), however, face challenges in waging that battle.

In 2006, the National Cooperative Highway Research Program issued NCHRP Synthesis 363, Control of Invasive Species. The synthesis identifies a number of challenges, with lack of funding being the principal one. Not surprisingly, 53 percent of State DOTs responding to the survey conducted for NCHRP Synthesis 363 stated that lack of State funding was an obstacle for invasive species control. Thirty-eight percent cited limited Federal funding as a primary obstacle. Many also mentioned limited staffing and lack of dedicated personnel as obstacles. Overcoming these challenges in a time of limited resources and building on gained experience will be crucial to making progress in the war.

Executive Order 13112, signed in 1999, requires Federal agencies to prevent and control invasions of nonnative plants. According to the executive order, Federal-aid dollars can no longer be used to cause further introductions. In 2005, the Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (SAFETEA-LU) expanded eligibility for Federal funding for control of invasive species and environmental restoration. It did not, however, create new funding sources.

The Federal Highway Administration (FHWA) has provided research funding for affordable global positioning system (GPS) units and weed washers, plus technical support via field guides, newsletters, and workshops to inform State DOTs about control of weeds on the ground. FHWA also has crafted a National Environmental Policy Act (NEPA) process to assess the potential impacts of any action on invasive species. Meanwhile, States continue to be under pressure from adjacent public and private landowners, as well as State noxious weed laws and county weed boards, to increase best practices and do more with less.

On the other hand, the good news is that agencies, communities, and conservation groups are creating alliances across the country and developing strategies to increase awareness of the dangers of invasive species and ultimately counteract the weed attacks. These emerging alliances have learned that no one entity can win alone. After all, weeds do not respect political boundaries. Roads and highways connect or cross public and private lands, giving transportation agencies a unique responsibility in this battle.

Partnerships as Part of the Answer

A few examples at various levels of government illustrate the point that partnerships are especially important to increasing public awareness and thus helping to prevent the spread of weeds.

International-DOT partnership. In 2002, the Washington State DOT joined with counterparts in Okanogan County, WA, and British Columbia to sign a memorandum of understanding (MOU) to work together in weed prevention and control. The partners include invasive plant councils, local DOTs, counties, and university extensions from both sides of the border. Together, these groups have produced calendars, field identification guides, and signage. Each year, the partners invite policymakers, the media, landowners, and the public on border-crossing tours to increase awareness about the obstacles and opportunities related to controlling invasive plants across international borders. FHWA provided funding for this partnership

Statewide cooperation. In Oregon, statewide efforts are showing impressive results, as reported by Tim Butler, supervisor of the Oregon Department of Agriculture's Noxious Weed Control Program, in a 2009 press release. One example of the State's notable success occurred in southwestern Oregon where a partnership of State, local, and tribal governments, along with private landowners, eradicated an infestation of more than 300 acres (122 hectares) of a weed called Paterson's curse soon after it was detected in 2004. The weed now is considered 90 percent contained.

Indian Nation-DOT partnership. In 2009, the Minnesota Department of Transportation (Mn/DOT) and the Fond du Lac Band of Lake Superior Chippewa in northeastern Minnesota signed the first MOU with an Indian Nation to reduce chemical use, conduct an inventory of vegetation, and control invasive plants along State highways within the reservation's boundaries. Mn/DOT and the Indian Nation invested many months to build trust and common ground. In 2009, FHWA recognized this partnership as a joint Exemplary Human Environment Initiative/Exemplary Ecosystem Initiative.

Adirondack Park-DOT partnership. In 2002, the New York State DOT, the Adirondack Park Agency (APA), and many State agencies and conservation groups signed an MOU to control four invasive plants in the park and prevent future invasions. A geographic information system (GIS)-based plant inventory created a baseline for control methods used on common reed, Japanese knotweed, purple loosestrife, and garlic mustard. These activities led directly to the APA issuing a general permit for control practices that previously required lengthy reviews, public comment periods, and individual permits. This effort has successfully kept these four target species from proliferating in the park.

Statewide-DOT partnership. In 2008, the Georgia DOT signed a statewide, private-public sector MOU to unite in an effort to prevent and control the spread of cogongrass in Georgia. This action escalated the war on weeds to a much higher level. In 1911, this aggressive grass was introduced accidentally in packing materials in another southeastern State. Later, it was planted purposefully as forage and became invasive to some 500,000 acres (202,500 hectares) in the Southeast, where it contributes to hot and fast wildfires. By focusing the resources of a partnership on a single invader, Georgia's approach could be a model for adjacent States for an all-out attack on cogongrass.

Dividing the greater Yellowstone area into manageable units based on ground conditions and weed invasions helps landowners and agencies coordinate weed control across millions of acres. Each shaded area represents a multijurisdictional public-private partnership to control weeds.

Additional Successful Approaches

What is needed to help ensure that the war will be won? In NCHRP Synthesis 363, State DOTs stated that documenting the costs and benefits of controlling invasive species is critical to obtain personnel and funding resources. Also, prevention and prompt control are essential to hold down long-term costs.

Based on detailed cost data from a control effort for tall whitetop, researchers from the University of Nevada conservatively estimated that delaying control for 6 years would double costs in the best-case scenario and more likely triple them due to rapid spread of this noxious weed. Many other invasive weeds show the same ability to expand rapidly if left untreated.

Training also is critical. The California DOT (Caltrans) began hosting workshops in 2005 to train crews to inventory the locations of more than 125 weeds that threaten the State's economy and ecology. The Utah DOT offers an annual training academy that has resulted in early detection of invasives that cross the State's borders.

State DOTs also can benefit from sharing information about innovative practices. For example, the use of controlled grazing by goats and sheep is a documented, low-cost, and low-impact way to control invasive species. The Wyoming DOT estimates that maintaining land grazed by sheep costs $18.80 per acre, compared to $185 to $310 an acre using herbicides, and $350 an acre using hand-cutting and mowing. Private contractors are now providing grazing services using goats specifically raised for controlling weeds.

The Wyoming DOT and county partners use an integrated weed management system so that the agency has the lowest herbicide expenditures of any DOT in the United States, while managing a 7,000-mile (11,265-kilometer) system.

(L-R): Lance Skelton, Kirkes Harrison, and Les Hurlbert of Okanogan County (WA) Department of Public Works posted this first Weeds Cross Borders partnership sign, and more signs will come, both in British Columbia and Washington.

Roadways as Vectors

Despite increased efforts to stop the spread of invasive plants along highway corridors, weeds continue to expand from roads into adjacent lands—farmland, forests, and ranches. Whether invasive species migrate through highway corridors naturally or via maintenance or construction practices is a subject of debate. However, mud on the tires of bulldozers or debris on the blades of mowers can easily transport seeds or vegetative parts of invasive species from one site or project to the next.

Through Small Business Innovation Research grants, FHWA supported the development of an affordable weed washer to remove soil and vegetation from the undercarriages of construction equipment and thereby diminish invasions caused by maintenance practices. Weed washers for highway maintenance and construction use are expected to be available by late 2010.

Searching for Solutions

Since 1999, based on the mandate from Executive Order 13112, FHWA has encouraged State DOTs to inventory invasive plants and other vegetation along roadsides. The other plants include endangered species, native remnants, and existing plantings.

"A geographic inventory of key roadside vegetation types is essential for highway right-of-way managers as a basis for communicating and coordinating best management practices to effectively control unwanted species while preserving those that have value to highway operations and maintenance," says Raymond Willard, roadside maintenance program manager, Washington State DOT.

Comprehensive vegetation inventories can serve as benchmarks to measure performance of various management methods. What is working and what is not needs to be reevaluated annually, before deciding how to invest limited resources. At the same time, DOTs need to partner with other public lands agencies to share inventory information.

Vegetation managers need to know where the invasives are and where they are spreading, and they need to know this information now. One of the long-awaited tools for highway vegetation managers is an affordable GPS and protocol. With so many GPS products available on the consumer market, singling out a tool that is convenient for vegetation managers is essential—a GPS that can be mounted on a dashboard, has good display visibility, is capable of recording necessary fields of information, is cost effective, and is compatible with other data formats used by DOTs.

With GPS data incorporated into a regional GIS database, decisionmaking is likely to become more effective because the manager then will have the big picture. To address this need, FHWA funded analysis by Mississippi State University of a GPS protocol appropriate to transportation needs and compatible with common handheld systems. Requisites for the protocol included requiring minimal training for learning to use it, meshing with early detection and rapid response capabilities, allowing incorporation into regional GIS data, and creating the foundation for providing decisionmakers with an overview of vegetation challenges. The protocol also needed to be compatible with national standards such as the accepted North American Weed Management Association standard. The Mississippi DOT and Mississippi State University worked with FHWA to develop the training manual, now available at

GPS units are now affordable inventory tools used daily by vegetation management crews. Mississippi State University and Mississippi DOT developed a protocol, field-tested the tool, presented inventory training in 2009, and developed the training manual shown here. This protocol will help identify where invasive weed infestations like the pictured kudzu are located and the effectiveness of DOT treatments over time.

A Land Ethic

"We are the road-buildingest nation on earth," former First Lady Claudia Taylor (Lady Bird) Johnson wrote in 1993. "And inevitably highways affect the lives of the people, for better or for worse. Therein lies both the glory and the burden of road building."

What follows logically is the glory and burden of maintaining highway corridors. Just as the transportation community is part of the problem, so it is also part of the solution, as demonstrated by the sample partnerships described earlier.

So is the war being won? In some States and regions and with some species...perhaps. At least a start is being made by adopting strategies that are expected to ultimately succeed.

In order to win, transportation vegetation managers need to reach out to all land managers and collaboratively adopt a land ethic—a commitment to environmental stewardship—or strengthen the ones they already employ. As part of this ethic, managers of highway construction and maintenance projects need best management practices to minimize impacts, especially soil disturbances. DOTs also must take advantage of innovative approaches, including those that are proven to reduce costs and environmental impacts. Perhaps most critically, all land managers and DOTs must respond quickly and effectively to new weed infestations in order to reduce long-term economic and environmental consequences.

"Protecting the utility, beauty, and intrinsic value of our roadside biota remains our responsibility. It's the only management decision that makes sense," wrote J. Baird Callicot and Gary K. Lore in an article, "Introducing a Roadside Land Ethic: It's Common Sense," in Roadside Use of Native Plants.

Best Management Practices

Whenever soils are disturbed during road maintenance or construction, the spread of invasive noxious weeds can result. Disturbances such as flooding, slope failures, or wildfires are beyond the control of DOTs, but the following practices can help avoid those disturbances that DOTs can control:

  1. Educate crews and contractors. The fundamental best practice is to train crews and contractors before any work begins so that they can identify weeds and control them.
  2. Preserve existing native remnants. The least expensive practice is to disturb as little vegetation and soil as possible when working on a project. This practice also saves time and materials.
  3. Eradicate before construction. Control weeds before project equipment moves into a site. This preemptive work minimizes the potential of weed spread during the entire construction project.
  4. Certify sand and gravel pits. Inspecting the pits in advance of a project allows for control of existing weeds and seeds before the pits are used.
  5. Certify weed-free mulch. Some 20 States already require contracts to specify the use of weed-free forage and mulch. This practice is one of the best ways to avoid spreading invasive plant seed.
  6. Use existing topsoils to create berms. Rather than importing topsoils potentially containing weed-seed banks, use existing topsoils to create berms along the perimeter of the project for later seeding.
  7. Temporary seeding. When a project ends at a season that is inappropriate for final seeding cover, use a temporary weed-free annual seeding for later replacement.
  8. Prequalify seed sources. To help agencies and contractors secure scarce seed, some States prequalify a list of approved seed sources.
  9. Minimize scalping and dredging of soils. Avoid scalping during mowing or ditch cleaning. If this kind of damage does occur, plant native grasses immediately.
  10. Clean equipment. Before moving to or from a maintenance or construction site, clean your equipment to minimize weed spread. Remove hanging debris and wash mud from undercarriage, tires, etc.

Mary Ann Rondinella is an environmental program specialist with the FHWA Resource Center Environment Technical Service Team. Prior to joining the Resource Center in 2003, she was an environmental protection specialist at the FHWA California Division. She also worked for the U.S. Department of Energy and the U.S. Army. She holds a B.S. degree in chemical engineering from Northwestern University.

Bonnie L. Harper-Lore, prior to her retirement from FHWA, was a restoration ecologist and headed FHWA's Roadside Vegetation Management Program. Harper-Lore is coauthor of Roadside Weed Management (FHWA-HEP-07-017) and editor of Roadside Use of Native Plants (FHWA-EP-99-014). She holds an M.S. degree from the University of Wisconsin-Madison.

For more information, contact Mary Ann Rondinella at 720-963-3207 or