In May 2019, the Division of Extension at the University of Wisconsin-Madison launched five Roadside Invasive Plant Management Workshops to provide industry insights and strategic tools to roadside vegetation management professionals throughout Wisconsin. Since then, many attendees have reported implementing noteworthy changes to their roadside vegetation management programs.
In total, 230 attendees from 53 municipalities, 25 counties, tribal governments, state and federal agencies, nonprofits and cooperative invasive species management areas attended the workshops. With those in attendance representing organizations responsible for the management of 19,800 centerline miles of Wisconsin roads each year, the workshops had the opportunity to influence vegetation management strategies for nearly 20% of Wisconsin roads. Key insights and takeaways from the workshops included:
Classroom sessions and tours of treatment test sites revealed herbicide applications to be the best method of control when compared with alternative strategies like mowing or hand-weeding methods. Multiple herbicide products were used on small- and large-scale test plots, including TerraVue® herbicide from Corteva Agriscience, and results consistently showed herbicide treatments to be more effective at controlling targeted plant species, regardless of the application site:
In the 18 months that followed, UW-Madison’s Division of Extension conducted three surveys to assess the impact of each workshop and identify shifts in management strategies among those in attendance. The results show that many of the state’s roadside vegetation management leaders are changing their approach.
Survey respondents specified a variety of challenges encountered by their vegetation management teams. As the initial average of roadside right-of-way miles receiving herbicide applications was below 25% for all municipality, county and department of transportation entities that responded, there is a significant opportunity for their teams to effectively address the following roadblocks by increasing their use of herbicide applications.
Mowing too early in the treatment season allows targeted vegetation to resprout and flower, leading to viable seed production without additional mowing treatments. Comparatively, mowing too late in the treatment season can distribute seeds along roadsides and support the spread of invasive species. To avoid these issues, practitioners are encouraged to consider the benefits of using a selective herbicide like TerraVue, which delivers effective weed control against 140 broadleaf weeds and woody plants, including wild parsnip (Pastinaca sativa).
Mechanized mowing may be used by vegetation management teams working to control incompatible vegetation along roadsides, but selective herbicide applications can provide significant cost savings. While mowing can stimulate regrowth and resprouting, selective herbicides control targeted plant species more effectively without disturbing native plants throughout the treatment site. For vegetation management programs, reduced maintenance costs are a significant benefit of using herbicide applications as well.
Cost comparison of treatment methods referenced in the 2019 roadside workshops.
County and municipality representatives who were surveyed reported that anywhere from 32% to 46% of their right-of-way miles are mowed at least twice annually. Unfortunately, the ideal treatment window for these strategies lasts for only a few weeks each year. Couple that with budget restrictions and a shortage of skilled workers, and treatment strategies often fall short of desired results. Various methods can be used to apply selective herbicide treatments throughout the year, making their lower costs and increased efficacy even more desirable to roadside management teams.
As a result of attending the workshops, fewer than 10% of all respondents reported plans to increase mowing frequency in the following year. While 0% expressed plans to decrease the frequency of herbicide applications, nearly 40% planned to alter the timing of herbicide treatments. Other noteworthy results include:
Survey results show that 86% of respondents made at least one change to their management technique after attending the workshops, and 50% made three or more changes. Put simply, the workshops have positively impacted vegetation management practices on nearly 14,000 centerline miles throughout Wisconsin.
As a result of attending the workshop, 41% of the participating organizations reported that they planned to increase the frequency of their herbicide applications in 2020. A follow-up survey in 2020 showed that 73% of those respondents had successfully adapted herbicide treatments as part of their vegetation management programs.
While the COVID-19 pandemic kept similar workshops and educational opportunities from being shared in 2020, the Division of Extension at the University of Wisconsin-Madison still hopes to expand these educational workshops in the future. For the time being, industry professionals interested in learning more about best practices for roadside vegetation management can visit the UW-Madison Division of Extension website or contact their Corteva representative.
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