Integrated Vegetation Management for Roadsides
Integrated Vegetation Management (IVM) can be thought of as quality management for roadsides. It is a decision-making system that considers a variety of tools to manage vegetation in an economically and environmentally sound manner. (See RCW 17.15 below.)
Vegetation along roadsides is managed for a number of reasons including maintaining visibility for drivers, reducing water on the roadway, protecting longetivity of the road surface, and minimizing fire danger.
IVM relies on consideration of all methods for controlling vegetation. Economics is also part of the decision making process. Arbitrarily discounting a pest control method upsets the balance of IPM. Mowing, use of beneficial insects, plant selection and herbicides are all appropriate tools depending on the site, funds available and management goals. Costs can be managed more effectively when they are prioritized within an IVM program. Prioritization ensures that the most important activities happen first.
Goals of an Integrated Vegetation Management program:
Provide Safe, Reliable Transportation
- Maintain visibility for drivers (Protects government from liability)
- Reduce water on roadway to prevent hydroplaning
- Keep sight lines open at intersections, driveways, pedestrian crossings, known animal crossings and on curves
- Maintain visibility of signs
- Prevent growth of trees and shrubs that obstruct road use
- Minimize fire hazards
- Prevent shading of pavement that allows formation/perpetuation of frost or ice on roadway
Maintain the Public’s Investment in Infrastructure
- Keep ditches and other drainage structures open to prevent water from impacting road users.
- Ensure drainage of water from sub base.
- Extend surface life of pavement by reducing frost heaving and sub-surface degradation caused by standing water.
- Prevent pavement break-up by plants
Operate Within Budget Limitations
- Utilize all resources efficiently and economically
- Measure actual vs. planned performance
- Implement corrective action as needed
Protect worker Safety
- Reduce worker risk and injury
Minimize Environmental Impacts
- Reduce the spread of weeds and control noxious weeds as required by law.
- Control erosion which reduces sediment movement to water, including fish bearing streams.
- Protect wildlife and birds from moving through less disturbance of nesting sites and habitat.
- Maintain roadway aesthetics
Making Decisions About Herbicide Use
Herbicide use can be an emotional issue for some constituents. Step back from emotion and examine the facts. Ultimately, the goal is to make informed decisions about how to best manage roadside vegetation on a limited budget.
Research, Testing and Registration of Herbicides
Herbicides are strictly regulated under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) FIFRA has been amended by Congress several times to create an increasingly comprehensive regulatory system.
On average, only one in 20,000 chemicals makes it from the laboratory to market. To ensure that a product, when used properly, will not present health or environmental concerns, it must pass to up to 120 separate tests. Pesticide development, testing and EPA approval takes eight to 10 years and costs manufacturers $35 million to $50 million for each product.
In addition to the above requirements for new herbicides, all older herbicides must go through extensive testing and re-registration to be allowed to stay on the market.
Safety is the overriding consideration in pesticide research and development. When used properly, products must not create an unreasonable risk to the user, the environment or the public. EPA requires that pesticide labels list precise application methods, doses and specific instructions to assure safety. Workers who apply herbicides are required by law to be trained, licensed and keep strict records.
Herbicides have been used for more than forty years to successfully manage a wide variety of weeds and other roadside vegetation.
Mowing vs. Herbicide Use
Depending on the terrain, traffic flow and other factors, mowing can be hazardous for both workers and drivers.
- Mowers travel 3-4 mph, sprayers travel 15-20 mph.
Mowers throw objects and debris into traffic lanes
Mowing may require up to 10 more treatments than spraying. That takes ten times the man-hours
Multiple studies show mowing costs 5-8 times higher than spraying per acre. Increasing road maintenance costs that much means less money for other needs
Defining Integrated Pest Management
RCW 17.15.010 “Integrated pest management” means a coordinated decision-making and action process that uses the most appropriate pest control methods and strategy in an environmentally and economically sound manner to meet agency programmatic pest management objectives. The elements of integrated pest management include: (a) Preventing pest problems; (b) Monitoring for the presence of pests and pest damage; (c) Establishing the density of the pest population, that maybe set at zero, that can be tolerated or correlated with a damage level sufficient to warrant treatment of the problem based on health, public safety, economic, or aesthetic thresholds; (d) Treating pest problems to reduce populations below those levels established by damage thresholds using strategies that may include biological, cultural, mechanical, and chemical control methods and that must consider human health, ecological impact, feasibility, and cost-effectiveness; and (e) Evaluating the effects and efficacy of pest treatments.
Resources for additional information
WSDOT Vegetation Management:
EPA Fact Sheet: Benefits of Integrated Vegetation Management on Rights-of-Way:
EPA Fact Sheet: Integrated Vegetation Management: