With more than 41,000 miles of road, South Carolina operates the nation’s fourth-largest state-maintained highway system. For the South Carolina Department of Transportation (SCDOT), miles, climate and diverse topography all translate into a road maintenance challenge.
Part of the solution is the agency’s integrated roadside vegetation management program. Ken Caldwell, an ISA-certified arborist, is the integrated roadside vegetation management coordinator for SCDOT’s District 4, which covers seven counties in the northern part of the state.
“My priorities are providing a safe roadway, maintaining adequate sight distances and controlling noxious and invasive weeds—all while maintaining aesthetically pleasing roadsides,” Caldwell said.
SCDOT uses an integrated roadside maintenance plan to keep these sight distances open and roadsides free from unwanted and potentially dangerous weeds and brush, including kudzu and wild lettuce, two of the most troublesome weeds in the area. Herbicide treatments play an integral role, and SCDOT’s District 4 does nearly all of its herbicide spraying in-house.
SCDOT uses Milestone specialty herbicide at 7 oz per acre on kudzu sites. “Milestone has proven to be a very effective tool in our herbicide toolbox, and it’s shown excellent control on kudzu,” Caldwell said. “And you can go back to the areas that we sprayed a year later and see residual results.”
On one stretch of I-85 near Gaffney, S.C., the wild lettuce had almost taken over areas in the median and shoulders.
“Wild lettuce was everywhere on this stretch of highway, and some was reaching 3 ft tall—making it very unsightly,” Caldwell said. “We applied 5 oz of Milestone per acre with a surfactant and antidrift adjuvant in a mixture at 20 gal per acre of total spray. The results were fantastic. One year after treatment there was a very noticeable difference in the amount of wild lettuce present. It also took out the thistles. It all added up to make a significant difference on this section of interstate.”
For Caldwell, and for many roadside managers, an aesthetically pleasing roadside starts with the presence of healthy grass. “We have quite a few types of desirable grasses that grow in our district, because the soil type varies from red clay to deep sand,” Caldwell said. “The dominant grasses are Bahia grass, Bermuda grass and fescue, and it is very important that we do not injure the turf that is in place. Our district is full of rolling hills, and we have quite a bit of topography, which makes it very important for us to maintain healthy grass on all these slopes in order to keep our roads secure and safe.”
Caldwell continued, “By controlling these weeds with little to no adverse effects on the desirable grasses, Milestone gives our turfgrass room to spread out, creates a much better stand of desirable grass and makes our interstate highways look much better.”
For SCDOT, finding ways to keep roads safe and beautiful for the motoring public is what it’s all about.
Rogers is IVM market development specialist, Dow AgroSciences.