Integrated Vegetation Management for Roadsides

Integrated Roadside Vegetation Management (IRVM) can be considered as quality management for roadsides. It is a decision-making process that considers a variety of tools to manage vegetation in an economically and environmentally-sound manner.

Vegetation along roadsides is managed for a number of reasons including maintaining visibility for drivers, reducing water and debris on the roadway, protecting longevity of the road surface, reducing erosion control, minimizing fire danger, and providing sustainable vegetation.

The Idaho Transportation Department IRVM program is a coordinated decision-making and action process that uses the most appropriate pest-control methods and strategies to meet the agency’s programmatic management objectives.

Our IRVM program relies on consideration of all methods for controlling and maintaining vegetation. Developing a successful IRVM program means one must consider all management practices, determine the desired result, and examine the facts.

Arbitrarily ignoring or discounting a pest control method upsets the balance of an integrated pest management approach. Management tools such as mowing, mapping invasive populations, using beneficial insects, herbicide applications, revegetation efforts, and plant selection are all appropriate and cost-effective depending on the site, funds available and management goals.

ITD objectives of a successful Integrated Roadside Vegetation Management program include providing safe and reliable transportation, maintaining infrastructure investments, operating within budget and personnel limitations, and minimizing environmental impacts.

Ultimately, the goal is to make informed decisions on how to best manage roadside vegetation and achieve effective results. Costs can be managed more effectively when they are prioritized within an IRVM program. Prioritizing ensures that the most effective activities take precedence first.

Elements of ITD’s Integrated Roadside Vegetation Management

  • Conducting roadside weed inventories and maintaining records of weed species and locations.
  • Determining acreage and density of the pest population.
  • Coordinating and scheduling roadside maintenance activities and mitigation measures to reduce the potential for overlap or duplicated efforts.
  • Reducing the presence of target pests and pest damage.
  • Monitoring the area for new invaders and developing EDRR strategies.
  • Treating pest problems and reducing pest populations using various strategies including biological, cultural, mechanical, and chemical control methods that consider human health, ecological impact, feasibility, and cost-effectiveness.
  • Evaluating the effects and efficacy of pest treatments and measuring the success or failure of prior treatments.
  • Planting desirable species in high impact areas to provide competition against reinfestation of target weeds.
  • Utilizing weed free mulch and compost material.
  • Minimizing the transport of invasive species and preventing the establishment of noxious weeds.

Mowing vs. Herbicide Use
Depending on the terrain, traffic flow, and other factors, mowing can be hazardous for both workers and drivers. Consider these facts:

  • Mowers travel at 3 to 4 mph; spray trucks travel at 15 to 20 mph.
  • Mowers sometimes throw objects and debris into traffic lanes.
  • Mowing costs range from $45 to $60 per acre; spraying costs range from $35 to $45 per acre.
  • Mowing may require multiple treatments and uses ten times the man-hours.

Case Study – I-84 Corridor Project:
Approximately five years ago a tour of treated cheatgrass infested sites for fuels management sparked the idea of an Interstate 84 corridor project. Since that time, individuals have identified a management plan and secured funding.

In 2004-05, fuel break development language was added to the SAFETEA-LU (Transportation Bill) to secure future funding for follow-up fuels projects, the Wildfire Impact Reduction Coalition (WWIRC) was formed and goals were established to encourage fuel breaks on roadsides, wildland/urban interface areas and for protection of critical habitat areas; Bureau of Land Management (BLM) implemented numerous small research fuel management projects using Plateau herbicide, BASF secured funding for monitoring and establishing additional field trials, and Idaho Transportation Department (ITD) completed evaluations of the I-84 fuel treatment options and vegetation types in preparation for implementing this demonstration project.

The purpose of this project is to utilize the I-84 corridor east of Boise as a demonstration fuel break to reduce fire frequency and intensity. Continuous treatment is needed within the defined areas for proper evaluation of the fuel break demonstration.

There is a high incident of wildfires across this stretch of highway, with a map available of wildfire history. After vegetation treatments are implemented, natural wildfire behavior across treated versus non-treated areas will be monitored through data collection and observation. New wildfire behavior in treated areas will be compared to recent and historic fire behavior. The results of this study will be published in a brochure as well as posted on the WWIRC resources website as a model for others to learn from and assist them in establishing future roadside fuel breaks.

The I-84 corridor contains intermixed areas of solid cheatgrass stands with areas of native vegetation infested with cheatgrass. The project area (fence-to-fence) includes ITD right-of-way, state and private lands, as well as BLM land. The maximum area to be treated is approximately 2,500 acres. Dependent on the specific area (cheatgrass load, slope, vegetation type, burn history, etc.), treatments would include mechanical (mowing), herbicide using Plateau and other approved herbicides, mechanical seeding and revegetation, and fuels treatments other than herbicide.

Agency contributions included:

FHWA contributing $25,000 for Plateau purchase, application, monitoring, etc.

  • BLM granted $400,000 to ITD to be used for noxious weed control, mowing, and herbicide applications other than Plateau;
  • BASF, hired a contractor to collect data and develop fire modeling applications;
  • Wildfire Impact Reduction Coalition (WWIRC) is in the process of posting project updates on the Internet, and
  • ITD has contributed approximately $15,000 in in-kind funds including seed species, seeding equipment and contract and project oversight.

Results of the 2005-06 treatments include Plateau treated in the burned and unburned areas resulted in 70 percent cheatgrass control achieved, non-burn areas containing a heavy thatch layer resulted in poor control of cheatgrass (less than 35 percent) with only visual stunting; control within five feet from the roadside was also poor, less than 35 percent control achieved; Plateau and Journey combined treatments in the burned areas, resulted in greater than 90 percent control of cheatgrass achieved throughout the area except within five feet from the roadside where less than 35 percent control was achieved; germination of drill-seeded desirable plants was excellent from the roadside to halfway to the fence and all seedlings appeared healthy, Plateau, Journey, and Telar combined treatments resulted in greater than 90 percent control of cheatgrass achieved throughout the area and germination of drill-seeded species was good; however, leaf yellowing was occurring in about half of the plants.

Applications conducted during 2007 include herbicide applications using Telar and Roundup combination, other herbicide treatments to reduce kochia and mustard species, mowing applications, as well as mechanical seeding applications with native and non-native fire resistant species to control annual grass competition.

Future objectives include collecting data and establishing monitoring sites to monitor residual cheatgrass control and seedling establishment (to be completed in fall 2007), identifying additional sites and acres for Plateau and Journey applications, and treating remaining acres using herbicide, mowing and mechanical seeding applications.

Published 10-18-13