Roadsides and Herbicides: TxDOT and the 3-Zone Approach

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Texas roadside

The Texas Department of Transportation employs a 3-zone approach to effectively manage incompatible vegetation on thousands of roadside miles each year. Learn how this vegetation management strategy uses various herbicide applications to not only enhance roadway safety, but also program efficiency and environmental sustainability.

Roadside vegetation management programs are structured to maintain the integrity of transportation infrastructure and keep roadway areas clear of vegetation that poses a threat to workers, pedestrians and drivers alike. Benefits of this work include visibility enhancements, hazard-free vehicle recovery areas and surface drainage improvements. When used properly, certain vegetation management strategies also can support the development and maintenance of biodiverse habitats for various wildlife species.

Why Use a 3-Zone Vegetation Mangement Program?

The Texas Department of Transportation (TxDOT) employs a vegetation management program that is structured to successfully achieve each of these results. From managing incompatible vegetation throughout rights-of-way (ROW) and driving surfaces to keeping clear zones safe and accessible, licensed pesticide applicators and vegetation management specialists with the TxDOT’s Maintenance Field Support Section provide multiple benefits to roadway infrastructure and surrounding environments throughout the state. These benefits include:

  • Improved pavement integrity
  • Erosion prevention
  • Areas for drivers to stop or regain control of vehicles that have left the roadway
  • Clear waterways to prevent flooding, cracks and potholes or slick driving surfaces

Equipped with more than 300 specialized pieces of application equipment, TxDOT is responsible for maintaining more than 800,000 acres of roadside rights-of-way. Given this vast treatment area and the size of its fleet, the agency uses selective and nonselective herbicide applications to enhance results, increase productivity and free up one of the most valuable resources of all — time.

Hand-pulling methods can be labor-intensive and time-consuming, and the exclusive use of mechanical treatment strategies during the growing season also leads to the detrimental cutting or removal of desirable vegetation. As a result of mowing exclusively, practitioners can inadvertently hinder the development of native plant communities and aid the reestablishment of problematic plant species.

Comparatively, the flexibility of various herbicide applications enables TxDOT to maintain total vegetation control on the roads and support the development of native plant communities on ROW land to form a natural barrier against incompatible vegetation. Only 14 herbicide products are currently used by TxDOT, but each chemistry plays an integral role in helping the agency achieve optimal results throughout the three zones that comprise its roadside vegetation management program:

Zone 1: The Vegetation-free Zone

TxDOT works to keep its roads and gravel shoulders clear of grasses, broadleaf weeds and noxious or invasive plants to support surface drainage, increase visibility, enhance roadside hardware maintenance and prevent pavement breakup commonly caused by plants. While many roadside vegetation managers use broadcast herbicide applications in this zone to maintain total vegetation control, TxDOT applies herbicide treatments to only green, actively growing vegetation approximately twice a year. This helps maintain total vegetation control, minimizes run-off and provides cost savings through the reduction of excessive applications.

Zone 2: The Operational Zone

Selective herbicide applications are used to maintain control of incompatible vegetation throughout the Operational Zone. This helps maintain hazard-free vehicle recovery areas and increase the hydraulic capacity of roadside ditches. Keeping vegetation at heights below 30 inches in this area helps practitioners support the development of regenerative ROW corridors that contain native plants and provide ample site distance for intersections as well as passing or stopping vehicles.

 Zone 3: The Transition Zone

Brush control is essential in the Transition Zone, as trees can not only interfere with site distance but also inhibit the development of beneficial native plant communities. Products like Capstone® herbicide and Vista® XRT herbicide from Corteva Agriscience are commonly used by TxDOT for treatments in this area as they help ensure ample screening for adjacent surroundings and support the establishment of native plants that represent biodiverse habitat for pollinators and other native wildlife species.

In areas featuring or adjacent to standing water, Vastlan® herbicide is commonly used to control encroaching trees and brush species, while selective chemical side-trimming applications are used in certain areas to treat only portions of trees that interfere with sight distance.

Regardless of the chosen application method, herbicide use is an exact science for TxDOT. That’s why the agency works with its applicators, operators and industry partners to ensure the safe, lawful and effective use of select formulations.


As stewards of the land, applicators and operators working with TxDOT are required to be licensed, trained and recertified annually. These professionals also are required to record all herbicide applications throughout the year. With the help of the agency’s Maintenance Field Support Section, as well as Vegetation Management Specialists with Corteva Agriscience, TxDOT also conducts extensive product research before any products are ever used in the field. This independent herbicide research helps confirm the efficacy and environmental impact of chemistries proposed for use before they are ever applied along roadsides throughout the state.

“We’ve helped establish research plots to support product and strategy testing,” said Troy Goodson, Vegetation Management Specialist with Corteva Agriscience. “The fact that TxDOT works to gather data to justify the use of its preferred herbicide products is a true testament of its commitment to enhancing roadway safety and environmental sustainability.”

Contributing to this research helps Goodson and other industry experts with Corteva familiarize themselves with the objectives TxDOT works to achieve each year, as well as challenges practitioners commonly encounter in the field.

“Before making any management recommendations or suggesting specific herbicide products for use, we like to gain a comprehensive understanding of each vegetation management program we support,” Goodson said. “Understanding a program’s goals, as well as the challenges it faces each year, enables us to effectively address the needs of our industry partners.”

Johnsongrass (Sorghum halepense), bermudagrass (Cynodon dactylon) and a variety of broadleaf weeds are common issues along roadsides throughout Texas, and species tolerance enables these problematic plants to become less susceptible to different chemistries over time. However, the extensive product research conducted by the agency helps operators identify alternative herbicide chemistries that can enhance not only efficacy and flexibility, but also cost efficiency and environmental sustainability.

In addition to native grasses, more than 5,000 wildflower species grow along Texas roadsides, which is why the agency buys and sows approximately 30,000 pounds of wildflower seed each year to rehabilitate areas affected by new construction and maintenance activities. Similar to the vegetation management strategies employed by TxDOT, its wildflower program is structured to reduce the use of mowing practices and support the development of grasses and wildflowers that help conserve water, control erosion and provide beneficial habitats for various wildlife species. TxDOT also is working to enhance public understanding of herbicide use through the agency’s #Fall4Flowers and #WildflowerWatch campaigns. 

Supported by flexible herbicide applications and its 3-zone approach to roadside vegetation management, TxDOT is able to leverage impactful treatment strategies that enhance roadway visibility and safeguard transportation infrastructure. Moreover, these industry best practices support the development of biodiverse wildlife habitat and enhance annual resource management.

To learn more about product recommendations and best practices for roadside vegetation management in your respective territory, visit


™ ® Trademarks of Corteva Agriscience and its affiliated companies. When treating areas in and around roadside or utility rights-of-way that are or will be grazed, hayed or planted to forage, important label precautions apply regarding harvesting hay from treated sites, using manure from animals grazing on treated areas or rotating the treated area to sensitive crops. See the product label for details. State restrictions on the sale and use of Capstone® and Vista® XRT apply. Consult the label before purchase or use for full details. Vastlan® is not registered for sale or use in all states. Contact your state pesticide regulatory agency to determine if a product is registered for sale or use in your state. Always read and follow label directions. © 2022 Corteva.


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