Kentucky Transportation Cabinet knocks out noxious weeds

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Image of two highways divided by grass, with cars and trucks driving

An increasing number of noxious weeds have infested many of Kentucky’s highway roadsides. With law stipulating optimized control on rights-of-way adjacent to properties in which invasive plants are treated, action is being taken to improve highway safety and the development of native plant communities.

Noxious weeds are a source of multiple hazards along roadsides across the United States. In addition to causing soil erosion, fire hazards and pavement damage, these invasive plants can grow large enough to restrict highway travel lanes, obstruct visibility for drivers and impede the development of native plant species. Every year, countless species of noxious weeds wreak havoc on roadsides across the United States. In an effort to mitigate these risks, vegetation management strategies are tested to determine best practices for controlling a variety of prevalent species throughout each state. Entrusted with the building of federal highways and the maintenance of transportation-related issues, state-funded agencies seek out solutions that can improve the cost-efficiency and efficacy of roadside treatment strategies.

With the well-being of the public and environments surrounding highway roadsides in mind, each state regularly explores management solutions to effectively control hundreds of broadleaf weeds and brush species. For Kentucky, a long-standing state law was modified in 2014 to mandate the eradication of select noxious weeds and invasive plants throughout all rights-of-way adjacent to properties in which certain species of invasive plants are being actively treated. While a variety of other incompatible plants are the subject of focus in regions throughout the country, the following weed species are currently identified for control on roadside rights-of-way in Kentucky’s noxious weed law:

·       Johnsongrass

·       Giant foxtail

·       Musk (nodding) thistle

·       Canada thistle

·       Multiflora rose

·       Kudzu

·       Posion hemlock

·       Marestail

·       Amur (bush) honeysuckle

·       Japanese knotweed

·       Common teasel

In accordance with this stipulation, the Kentucky Transportation Cabinet (KYTC) works to employ proven methods of control across all applicable sites. As a roadside environment state administrator for KYTC, Mike Smith identifies the overarching focus of the cabinet’s efforts.

“The control of state-listed noxious weeds and invasive plants benefit the environment and create more favorable conditions,” Smith says. “Safety is our No. 1 priority for all vegetation management activities.”

To keep all parties properly informed, KYTC also publishes a notice each year to property owners throughout the state. David Cornett, branch manager for roadside environment and vegetation management at KYTC, details these notices and the manner in which the state’s vegetation management program is implemented for noxious weed control.

“The law stipulates that we publish a public notice in early March of every year through the main newspaper for each of our 120 counties,” Cornett says. “This alerts property owners who are actively controlling noxious weeds on their property to notify the Cabinet of the need for noxious weed treatments on the rights-of-way adjacent to that property. However, we go beyond the letter of this law and plan weed control measures for all of the noxious weed species as a routine part of the program throughout the year.”

A Shift in Management Strategies

For over 50 years, KYTC has used physical and chemical methods to control a variety of invasive plants throughout the state. In the past, many roadside management programs have relied exclusively on mowing to control the spread of invasive species. However, results have shown this method to leave the root systems of many plants intact, which can inadvertently lead to higher invasive plant densities over time.

When noxious weeds and other invasive plants develop, they commonly encroach areas in which beneficial grasses and forbs would normally thrive. As incompatible plant species pilfer valuable sunlight and nutrients from desirable vegetation, KYTC works to establish effective control of invasive plants to help reestablish the natural development of beneficial plant communities. As noxious weeds can be aggressive, poisonous and difficult to manage, KYTC commonly uses selective herbicide treatments to enhance invasive plant control. Considering sensitive timing requirements associated with mowing alone, Smith recognizes the benefits herbicide applications provide and the industry’s gradual shift toward their use as a preferred management method.

“The Transportation Cabinet mows rights-of-way three times a year, including trimming around obstacles and litter removal,” Smith says. “Some urban routes receive extra cycles.”

For state-funded agencies like KYTC, increased mowing expenses and the need for more selective weed control are major factors driving change throughout the industry. Through the use of selective herbicides, practitioners are able to target and remove a variety of invasive plants, which allows compatible species like desirable grasses or beneficial forbs to thrive. As these native species flourish, the space available for invasive plants to grow is significantly reduced, which helps to improve conditions along highway roads and limit long-term maintenance costs for roadside managers. As the use of selective herbicides has been proven to enhance results and provide financial benefits for roadside vegetation management programs, associated strategies are quickly becoming industry best practice.

“Herbicides are an effective, economical and environmentally friendly method of weed control that are beneficial in comprehensive vegetation management plans,” Smith says. “Timely herbicide treatments help maintain roadway visibility, prevent weed reproduction and reduce the frequency of roadside mowing — our most expensive weed control method.”

A New Tool for Roadside Managers

This year, KYTC began using TerraVue herbicide from Corteva Agriscience in operational sized demos where a typical spectrum of weeds was present. There are plans in place to include TerraVue in small plot studies as well. Powered by Rinskor® active, a reduced risk herbicide that won the American Chemical Society’s Green Chemistry Challenge Award, TerraVue delivers effective weed control against more than 140 broadleaf weeds and brush species.

Using ATVs equipped with rear spray brooms, KYTC disperses the formulation with nonionic surfactant (NIS) at an application rate between 2 and 2.85 ounces per acre. For KYTC, early results have shown control of invasive species commonly found throughout Kentucky, namely buckhorn plantain, marestail and hedge bindweed. With more than 27,000 miles of routes to maintain and a variety of noxious weeds impacting countless highway infrastructures, KYTC will continue monitoring the impact of TerraVue as it works to enhance roadside safety and promote the development of dense, green roadside turf along interstate highways throughout the state.

For more information on TerraVue, recommended use sites and flexible application methods, click here.


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™ ® Trademarks of Dow AgroSciences, DuPont or Pioneer, and their affiliated companies or their respective owners. 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. TerraVue 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. Rinskor is a registered active ingredient. Always read and follow label directions.