Wyoming County Finds Favorable Leafy Spurge Control With Selective Herbicide
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One year after trying GrazonPD3 herbicide in a leafy spurge control program, we check in with the Weston County Weed and Pest Control District in Wyoming to hear about their experience and observations so far.
District Manager Hale Redding said, “It really exceeded my expectations overall. I was expecting more regrowth than what I saw, especially with some of the really old stands.” Find out what they saw, what they learned and how they plan to continue using this tool in their program.
For a prior TechLine article, we spoke with Hale Redding, District Supervisor, Weston County Weed and Pest Control District, about his experience applying GrazonPD3™ herbicide as part of the long-term leafy spurge control program in this Wyoming county. We caught up with Redding to see how the program is progressing and get his observations of GrazonPD3 performance. When we spoke, Redding had just revisited the treated areas and had some useful insights to share.
Response exceeds expectations
“This was the first time I’d visited the sites since last summer,” Redding said. “You could immediately see from far away which areas had been treated. In untreated areas, the leafy spurge was in full bloom and bright yellow.”
In contrast, treated blocks showed minimal regrowth. “You can definitely tell where our spray blocks were,” Redding said. “There is some leafy spurge there, but it’s almost stunted. It’s small and not in bloom.”
Redding was very pleased with the control. “We’ve been treating these areas for 18-plus years,” he noted. “We know we’re not going to get it all in one year. But this is probably the best I’ve seen in treated areas. There’s not a lot of push-through.”
Redding said the control is better than what they’ve experienced in the past using a combination of Tordon® 22K herbicide (picloram) and imazapic. “I was expecting GrazonPD3 to be better than straight picloram,” Redding said, “But it really exceeded my expectations overall. I was expecting more regrowth than what I saw, especially with some of the really old stands.”
Weston County also uses a goat grazing program for leafy spurge control. This provided a convenient comparison for Redding’s team. In areas that were intensively grazed, regrowth was treated with imazapic the following spring. “We basically saw the same result with intensive grazing and retreating that we saw with one application of GrazonPD3,” Redding said.
While the Weston Country program is primarily focused on leafy spurge, Redding noted that they do have some small areas of Canada thistle, which GrazonPD3™ herbicide picked up as well.
The fence line in this photo marks the edge of a treatment block for an area in Weston County where GrazonPD3 was applied a year ago. Yellow blooms of leafy spurge are clearly visible beyond the fence line, while the treated area remains clear. (Photo courtesy of Hale Redding)
2,4-D choline and a lower use rate
Redding attributes the good results they’ve experienced to the inclusion of 2,4-D choline in GrazonPD3™ herbicide. 2,4-D choline is 96% less volatile than 2,4-D ester. While applications that combine picloram and 2,4-D as separate ingredients can result in a use rate of 64–80 fluid ounces per acre or more, GrazonPD3 use rates range from 40–80 fluid ounces per acre. In Weston County, they used a rate of 64 fluid ounces.
Based on this positive experience, Redding is looking to mix 2,4-D choline products, such as Freelexx® herbicide, with compatible partners to enhance control of other problem weeds, especially whitetop (also known as hoary cress), which Redding says has exploded in the area this year.
Of course, for Redding and other land managers, one of the most important factors in a weed control program isn’t just what vegetation is removed, but what beneficials are left behind. Redding said that with GrazonPD3, he did observe some minor collateral damage.
“Sometimes leafy spurge is growing up in stuff you want to keep. We have a lot of sagebrush, which his great for deer and antelope to hide in. We have seen some sagebrush thinning [with GrazonPD3] but it’s not being killed off.”
The thinning isn’t necessarily completely undesirable either. “Where sagebrush is thinned, that does open up ground for native grasses to come back, which enhances grazing,” noted Redding.
Lessons in application
The GrazonPD3™ herbicide application in Weston County relied mostly on aerial spray, with some side-by-side application in select areas. While both techniques yielded similar results, Redding likes the uniformity that aerial application provides.
Redding noted that most areas of leafy spurge regrowth were in locations that were shaded or near trees — spots that the aerial application would naturally miss or that the pilot avoided for buffering purposes. Redding is hoping to gain approval and funding for drone application in the near future, which will allow for even more accurate treatments.
A year after initial use, Redding reiterated his advice on application. He said, “Our biggest takeaway was: Talk to your pilot and contractor to know what their package preference is. We did two-gallon jugs last year, but this year we’ll do more with the totes. That’s less packaging and less waste. We find the helicopter loader and summer crews also appreciate that there is less to handle and not so many jugs to triple rinse and recycle.”
Redding and his team plan to treat new blocks of leafy spurge and will not be retreating any areas. “The regrowth is so small, we can’t really spot it,” Redding said. At the time we spoke, Redding was mapping out the year’s treatment areas, with a plan to check results in the fall.
For those thinking of trying GrazonPD3, Redding said, “If you’re used to using Tordon 22K only, this will broaden your reach with what you can get. I think they’ll be happy with the results. The 2,4-D choline really enhances the product. It’s a game-changer.”
GrazonPD3™ and Tordon® 22K are Restricted Use Pesticides. 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. Consult the label before purchase or use for full details. Freelexx, GrazonPD3 and Tordon 22K are 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. Always read and follow label directions.
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