A Win Over Wild Parsnip

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Wild parsnip Photo Credit : Leslie J. Mehrhoff, University of Connecticut, Bugwood.org 

Imagine you’re an EMS worker or tow truck driver and you’ve just come back from clearing a car crash from the side of the highway. It’s hot, so you’re in short sleeves. You didn’t notice the plant with the small yellowish-green flowers, but as soon as you step into the sun the next day, blisters start popping up on your arms. 

What you have is a classic case of phytophotodermatitis – a sunburn-like reaction to exposure to plant sap that is then exposed to sunlight. The likely culprit? Wild parsnip. 

A Win for Wisconsin Highways: Would it Work for You?

County highway departments in the upper Midwest have been fighting wild parsnip for years. Today, thanks to strategic use of selective herbicides, not only is wild parsnip being brought under control – highway departments are seeing reduced overall vegetation management (VM) expenses, improved equipment utilization, and an increase in overall plant diversity. It’s a win-win-win, say Rick Schulte, Nutrien Solutions; Lee Shambeau, 4 Control, Inc.; and Tanner Smith, Vegetation Management Specialist, Corteva Agriscience.

Recognizing the Opportunity

Schulte and Shambeau had noticed that several Wisconsin counties were spraying products like TerraVue® herbicide exclusively for wild parsnip, while still mowing roadsides and medians four to five times per year. 

“Lee suggested we include a plant growth regulator like imazapic in the tank mix, and the idea really took off,” Schulte says. “When you add the other herbicide, and when you consider the fact that the crew is already there on-site making the application, it just made sense. We were able to achieve a high level of grass control without mowing, and without making additional spray applications beyond what the counties were already doing for wild parsnip.”

Nutrien Solutions made the process even easier by providing a pre-mix in convenient refillable, returnable containers, and by including surfactants and drift control agents – a real bonus for crews that hadn’t had a ton of chemical-handling or application experience, and didn’t have dedicated spray equipment. 

“A lot of these counties are using the trucks they’d use in the winter for deicing,” Shambeau says. “They may be doing a little bit of fabrication work to add a mechanism for moving the spray up and down, but otherwise it’s the same equipment. County commissioners love that those trucks aren’t sitting idle all summer!”

Not Just Budgetary Benefits

And while mowing hasn’t been completely eliminated, counties that have adopted these Integrated Vegetation Management (IVM) principles have noticed significant cost savings. 

“What we’re finding out now is that we can go back and mow those areas we’ve sprayed, for a lot less,” Shambeau says. “Some of these counties are reporting back to us that their maintenance shop is less busy because the mower operators can see cinder blocks, rocks and tires, so they’re not running over them and damaging the mowers; they’re extending the life of the equipment. So there are cost savings there beyond just the reduction in mowing that I don’t think we always consider.”

And the benefits go well beyond just simple cost savings. 

“There are still regulations governing management of the right of way, and how high the weeds can get,” Smith says. “But by only mowing half as much, we allow the native forbs to grow; we allow the milkweed to grow. And by thinning the invasives like wild parsnip, there’s greater plant diversity.”

It all adds up to a win for selective herbicides and for IVM practices.

“The counties that have been doing this for two or three years are seeing the reduction in mowing as a key benefit,” Smith says. “But we’re also seeing all the other benefits we’d ordinarily associate with an IVM program cascading from there.” 

Under normal field conditions, TerraVue® is nonvolatile. TerraVue has no grazing or haying restrictions for any class of livestock, including lactating dairy cows, horses (including lactating mares) and meat animals prior to slaughter. Label precautions apply to forage treated with TerraVue and to manure and urine from animals that have consumed treated forage. 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. Consult the label for full details. Always read and follow label directions.

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