Proper procedures and equipment are key to effective herbicide applications on cut tree stumps in rights-of-way.
When tackling troublesome trees along roadsides and in utility rights-of-way and other areas, a variety of treatment options are available, including cut stump applications. Cut stump herbicide treatments, which work well for hardwood species, have several benefits: efficiency, accuracy, and less regrowth.
Cut stump spray treatments involve cutting down trees and applying an herbicide mixture to the cut surface. "Top growth can be removed with pruning shears, a sharp axe, a chain saw, or hydraulic shears attached to a skid-steer loader," says Robert Lyons, Ph.D., a professor and extension range specialist at Texas A&M AgriLife Extension Service. "Then the stumps are sprayed with a small but potent concentration of herbicide directly onto the cut stumps to prevent regrowth."
Lyons says cut stump treatments may be the best approach on woody invasive plants with stems larger than six inches in diameter because these plants tend to have rough bark. "Most woody plants in Texas are sprouting species in which new stems arise from dormant basal buds," he explains. "These sprouts grow rapidly because the large root systems remain alive and functional."
He adds that properly applied herbicide treatments can be highly effective for killing the crowns and roots of woody plants.
For a proper cut stump application, spray every cut stem. One stem on this tree was not sprayed and regrowth has occurred. Photo credit: Texas A&M AgriLife Extension Service.
For hardwood species such as blackbrush, elm, mesquite, oaks, and Texas persimmon, Lyons recommends using a mixture of herbicide and diesel fuel oil or vegetable oil. "Diesel fuel oil and vegetable oil act as coating agents and penetrants to ensure good coverage and absorption of the herbicide," he notes.
Dave Krause, vegetation management specialist for Arborchem Products in Mechanicsburg, Pa., notes that when using an oil mixture, the treatment area should include the cambium, the entire circumference of the bark, and exposed roots. "Lightly spray all bark and exposed roots of cut stumps with the herbicide mixture until it is wet but not dripping," he explains.
He adds that the key advantage of an oil-based mixture is that it can be applied any time after cutting. "Water-based cut surface treatment must be applied immediately after cutting or frilling," Krause explains.
Spray the entire cut surface and bark from the cut to the ground. A portion of this cut stem was not sprayed. Photo credit: Texas A&M AgriLife Extension Service.
"Basically you are applying the herbicide in an oil that will be absorbed through the bark and then move into the cambium layer for translocation throughout the vascular system and into the roots," Krause adds.
Follow these procedures to gain the best results with cut stump herbicide treatments:
Prep the area
- Cut every stem close to the soil surface.
- Make sure all surfaces of the remaining stump are clear of soil or debris.
- Note that using vegetable oil instead of diesel fuel oil as a herbicide carrier increases the cost but may be desirable in some situations.
- Add EPA-approved blue marker dye to the herbicide mixture to see that the entire stump is sprayed, and mark the stumps that have been sprayed.
- It's best to spray stumps immediately after cutting, Lyons notes.
- Adjust nozzles to deliver a coarse mist.
- Position the spray nozzle on a backpack or handheld sprayer directly over the cut stump so that the spray will reach the entire stump.
- Spray the entire cut surface and bark from the cut to the ground, especially the outer edges.
- Spray every cut stem.
- Remember that cut stump treatments are low-volume applications. Use only enough pressure for a good pattern to thoroughly cover the targeted area. "Typically less than an ounce per stem is required," Krause notes.
- Do not apply herbicides mixed with oil into water.
Keep in mind
- Apply herbicides at any time of the year, but for best results apply during the growing season.
- Consider using ready-to-use custom herbicide blends to avoid mixing errors.
- Follow the directions on the herbicide label.
- Take note of new herbicides for cut stump applications as they come onto the market because they may get into the cut surface more quickly and easily.
The product used in cut stump herbicide treatments needs time to move, even during the growing season, Krause cautions. "You'll know the treatments worked when you don't see new growth, or small brush turns brown and dies during the growing season."
Get the best from equipment
After removing above-ground tree growth, apply herbicide with a pump-up garden sprayer, backpack sprayer, or paint brush.
Another way to apply the herbicide to cut stumps is to attach an applicator to a mower. "We've been using the Tiger WetCut system for several years to mow off the brush and then anything cut gets sprayed," says Don Scholten, maintenance superintendent for the Lincoln County Highway Department in Minnesota, who treats trees such as volunteer ash, sumac, and willows.
He says the spray controller has a number of benefits: an automatic rate control system; safety, because no one is following behind the mower to apply herbicide; and efficiency, since one worker can do the job. "The spray controller has the option of a digital read of the application rate and system pressure," he adds.
Here's how to get the most from equipment used for cut stump herbicide treatments:
- For hand-sprayer applications, use an adjustable cone nozzle that provides the best pattern while maintaining the required small volume.
- Release the pressure in the sprayer daily to help increase the life of the seals and prevent accidental discharge.
- Make sure the sprayer and wand are not bent or damaged when stored in trucks.
- Check the filters in the spray wand handle weekly.
Debbie Coakley is a freelance writer in Warrenville, Ill.