By Michael Fleming, BASF Corp.
Close only counts with horseshoes and hand grenades; not with herbicides. For years, conventional thinking assumed that cut-stump and basal treatments on rights of way (ROWs) resulted in less herbicide deposited off-target than foliar applications. But is this conventional wisdom really accurate? If not, what does this mean for your integrated vegetation management (IVM) program?
To find out, the utility companies that work with the IVM Research and Development Program at the State University of New York College of Environmental Science and Forestry (SUNY-ESF) approached researchers Dr. Chris Nowak and Ben Ballard. They wanted to know the off-target herbicide deposition associated with common herbicidal tree removal techniques.
“Our big question was how much chemical is hitting the ground and getting into the ecosystem,” said Craig Allen, manager of distribution forestry at Niagara Mohawk, a primary partner in the SUNY-ESF research. “Because you may see vegetation brown-out after foliar applications, the layman’s perception is often that these techniques are putting more chemical into the environment. We wanted to know what is really happening, so we can be sure we’re making the right vegetation management decisions.”
The SUNY-ESF study compared the herbicide deposition of four conventional vegetation management techniques-cut-stump, basal, high-volume foliar and low-volume foliar-on New York ROWs. Trees were treated with herbicide mixes containing a fluorescent dye to track and measure how much chemical landed off-target with each application technique.
The research results were surprising. On a per-tree basis, basal and cut-stump treatments produced off-target deposition of nearly six times more herbicide than high-volume foliar treatments and almost 70 times more herbicide than low-volume foliar treatments.
“Foliar treatments can give the wrong impression,” Ballard said, “because although you’re putting a tenth of the active ingredient down compared to a cut-stump or basal treatment, the area affected-at least in the short term-looks like a lot more.” Ballard explained that what’s really happening is vegetation cover catches some of the chemical. This can be seen as brown on the landscape, but most of the area is only temporarily affected and vegetation comes back.
“What’s important to note is that the research shows that because they use different application methods and levels of chemical concentration, foliar treatments inherently deposit less herbicide off-target than cut-stump and basal treatments,” Ballard concluded.
Comparing Foliar Techniques
The SUNY-ESF research studied the high-volume foliar technique by applying a tank mix of Tordon K (.06 percent picloram active ingredient by volume) and Garlon 4 (.23 percent triclopyr active ingredient by volume) with a hydraulic tank and a skidder-mounted sprayer. Low-volume foliar applications were made with a tank mix of Accord (2 percent glyphosate active ingredient by volume) and Arsenal herbicide (.14 percent imazapyr active ingredient by volume) and a hand-powered backpack sprayer.
While foliar techniques deposited significantly less herbicide off-target than the basal and cut-stump applications, the research also showed a notable difference in herbicide deposition between the high- and low-volume foliar techniques. The high-volume foliar application of Tordon and Garlon deposited 11 percent of herbicide off-target, while the Arsenal and Accord low-volume foliar techniques deposited only 4 percent of herbicide off-target.
Foliar Techniques that Minimize Deposition
Nowak and Ballard found that making minor adjustments in application technique can minimize the deposition difference between high- and low-volume foliar techniques. For example, some areas in New York use a technique called a low-volume hydraulic application. With this technique, applicators use the same high-volume equipment but make the application at a lower pressure and with a chemical mix that’s closer to the mix of a traditional backpack treatment.
Basal and Cut-stump Deposition
The basal treatment studied by Nowak and Ballard was a tank mix of Garlon 4 (12.3 percent triclopyr active ingredient by volume), Stalker herbicide (.3 percent imazapyr active ingredient by volume) and oil applied as a spray to the lower part of target tree stems. Cut-stump treatments were applied with a spray bottle and a tank mix of Accord (16.6 percent glyphosate active ingredient by volume) and Arsenal (.6 percent imazapyr active ingredient by volume).
“While the area affected by foliar treatments was larger than with basal and cut-stump treatments, the total amount of herbicide that hit the ground was significantly more with basal and cut-stump applications,” Ballard said. According to the study, cut-stump applications can result in 48 percent of herbicide landing off-target, compared to just 4 percent to 11 percent for the other treatments studied.
Reducing Cut-stump Deposition
More herbicide lands off-target with an application like cut-stump for two main reasons. First, cut-stump chemical mixes typically have a higher concentration of active ingredient. Second, as the SUNY-ESF research found, the cut-stump technique itself can result in over-application. Modifying the cut-stump technique, however, can reduce the total amount of over-application.
According to Nowak and Ballard, rather than use a wide spray pattern to treat a stump, as done in this study and in conventional cut-stump treatments, applicators can reduce the amount of herbicide deposition by using a narrow stream of herbicide applied just to the cambial area. A companion study showed a 50 percent reduction in the total amount of herbicide used when this modified cut-stump technique was employed.
This modification is consistent with the approved uses of the herbicides used in SUNY-ESF cut-stump application; both the Arsenal and Stalker labels specify that the cambium area only should be treated. Other herbicides conventionally used with the cut-stump technique, like Garlon 4, require the entire stump to be treated with herbicide.
Using a narrow stream of herbicide applied just to the cambial area can reduce the total amount of over-application in a cut-stump treatment.
“The SUNY-ESF cut-stump findings have important management implications for Niagara Mohawk,” Allen said. “We’ve facilitated training for applicators to teach them how to modify this technique and control over-application. We can get the same efficacy with a third less chemical by being more selective with the cut-stump technique, so it’s a win-win situation. We’re putting less chemical into the environment and saving money.”
What You See-and What Your VM Program Gets
“All treatments result in off-target herbicide deposition,” Ballard said. “But the difference between the treatments can be striking. For some managers, our herbicide deposition research confirmed the deposition they suspected, but in other cases it’s actually challenged what they thought they knew. In any case, now they’re able to weigh deposition with all the other factors-cost, over-spray, non-target effects and efficacy-to make informed IVM decisions.”
The SUNY-ESF deposition research has had important implications for Niagara Mohawk’s program. Allen says the research proved what they suspected: that low-volume foliar puts less chemical into the ecosystem. “As a result, our state environmental agency approved Niagara Mohawk’s use of low-volume treatments in the wetland areas we manage,” Allen said. “Our main objective is to be a good environmental steward and now we can use low-volume foliar applications and know we’re impacting the environment as little as possible.”à¢®à¢®
Michael Fleming is a vegetation specialist with BASF Professional Vegetation Management Group covering the forestry, aquatic, utility and roadside markets in the Northeast. Editor’s note: Always read and follow label directions. Arsenal and Stalker are registered trademarks of BASF. Tordon, Garlon and Accord are trademarks of Dow AgroSciences LLC.