Mike Maurer, roadside district manager II with Pennsylvania DOT, works closely with Pennsylvania State University researchers to identify the best weed-control solutions for the state's roadsides.
Measure herbicides to ensure maximum effectiveness at the lowest possible level of active ingredient.

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.