Poorly maintained roadsides present a plethora of potential liabilities. Out-of-control vegetation creates safety hazards, erodes roadsides, spreads invasive plants, and degrades water quality. When flair mowers and other equipment can't do the job in hard-to-reach areas, many departments turn to herbicides.
“Many of our primary roadways include steep hills and sudden curves,” explains Mike Maurer, roadside district manager II with Pennsylvania DOT's (PennDOT) Pennsylvania Engineering District 12. Maurer, a 33-year industry veteran, oversees vegetation management along 3,800 miles of roads. “If grass or brush along these corridors grew to unruly heights, drivers wouldn't be able to see around corners. However, these areas are also impossible to mow. To keep the grass from growing too tall, we spray it once every spring.”
With hundreds of herbicide products on the market and up to a dozen more introduced each year, selecting a chemical concoction that balances the fine line between annihilating all vegetation versus just the unwanted weeds is a science.
This is why PennDOT, a leader in vegetation management programs for nearly 20 years, works closely with researchers at Pennsylvania State University (Penn State), who test new technologies every day.
Rand Swanigan, roadside management specialist with Missouri DOT (MoDOT) and board member of the National Roadside Vegetation Management Association, agrees that working with academia is a good way to test new herbicides. But in addition to partnering with the University of Missouri, he also works with herbicide manufacturers that have dedicated research and development programs: “We have a great working relationship with Dow, DuPont, Monsanto, BASF, and others,” he says, adding that these companies also work with universities to test products, often while the formulations are still numbered compounds and haven't been named. Still, after all that effort, MoDOT spot-tests new formulations before adding them to its list of approved herbicides.
In fact, MoDOT's process for selecting new products involves several steps.
First, departmental policy statements are taken into consideration. For example, the department doesn't use re restricted-use products, so it eliminates herbicides that fall under that category.
Then it conducts industry research, by attending trade shows and contacting herbicide manufacturers and other DOTs, to determine if there's a product already on the market that targets a particular species or challenge.
And finally, before placing an herbicide on its bid list, the department performs large-plot field testing in real roadside conditions, which Swanigan says takes at least one year.
In 2004 PennDOT and Penn State tested two new herbicides, BASF Professional Vegetation Management's Plateau and Overdrive, to see if they'd provide equal or better growth regulation and broadleaf weed control than the department's existing herbicide mix. Weeds like mile-a-minute weed, foxtail, poison hemlock, a variety of thistles, ragweed, and teasel overrun Pennsylvania's rights of way if not treated quickly, but desirable plants—such as fescue grasses—need to stay in place to control erosion.
In 2005, test plots indicated that Plateau controlled late-season foxtail, an undesirable grass that germinates from late May throughout summer and had been difficult to control with existing bareground herbicides, while providing growth suppression and seedhead control.
Overdrive worked as well, if not better, than other tested products to control mile-a-minute weed along with other broadleaf weeds.
“I was surprised to see the results rendered on foxtail, and happy to know I'd finally found a solution to a longstanding problem,” says Maurer. “Before these trials, I hadn't found any mixes that provided season-long control.”
Using a growth-regulator mix that consists of 2 ounces of Plateau for fescue seedhead suppression and 6 ounces of Overdrive for broadleaf weed control, Maurer has saved more than $11/acre because of the reduced labor costs, as well as the lower active ingredient level and product cost of the BASF herbicides.
“That difference really adds up at the end of the year,” Maurer says. “And it certainly helps me justify my program when budget discussions come under annual review.”
He also revamped his bareground program, incorporating Plateau into a solution that keeps guardrails completely clear of vegetation. The bare-ground application is the first treatment of Maurer's season, which begins in April or May. Crews apply a tank mix of 10 ounces of Plateau and 2½ quarts of BASF's Pendulum Aqua-Cap along with Krovar and Oust Extra, both made by E.I. du Pont de Nemours and Co.“We'll keep researching the latest and greatest products and procedures out there,” says Maurer. “By doing that in the past, we've managed to take care of problematic vegetation and save budget dollars.”