Beginning in 1995, NCDOT has been in the process of converting eastern and piedmont rights-of-way from traditional species including tall fescue (Festuca arundinacea) to centipedegrass (Eremochloa ophiuroides), a turf species that requires less maintenance. Plant growth regulators (PGR) have also been implemented into the vegetation management plan on tall fescue and bahiagrass (Paspalum notatum) roadsides which make up 55% and 27%, respectively. By utilizing PGRs, vegetative growth is reduced.
Centipede grass is a low maintenance turf species, which prefers acid soils and minimal fertility, conditions typically found on roadsides. Allowed to grow naturally, centipede grass reaches a mature vegetative height less than eight inches, creating a no-mow situation.
Research has shown that, if the application of a PGR is performed in a timely manner, vegetative and seedhead suppression is achieved. Utilizing PGR programs, the number of mowing cycles can be reduced from five to two or three cycles per growing season and in the case of bahiagrass, seedhead production is totally eliminated if applied in a timely manner. This allows maintenance budgets to be reduced while safety is increased to motorists and NCDOT employees.
Centipede grass has been successfully established in many of the areas throughout the piedmont and coastal plain of NC and has reduced maintenance inputs. However, broomsedge (Andropogon virginicus), a clump forming perennial weed has invaded many of these areas. Broomsedge, when allowed to grow, reaches a mature height between 18 and 36 inches. The areas contaminated with broomsedge are aesthetically unpleasing and safety is decreased in these areas. Where centipedgegrass is the primary desirable turf, the only current option is to mechanically mow the areas contaminated with broomsedge. This practice only reduces the foliar growth temporarily and does not reduce the population. Again this is the only management option available as no selective herbicide exists, registered or experimental, that controls broomsedge without harming centipedegrass.
However, much research has focused on pesticide placement technologies. Commercially available equipment which utilizes this technology includes the Burch Wet Blade, the Weed Bug, and the Brown Brush Monitor. The Burch Wet Blade and the Weed Bug function based on a height differential between the targeted weed species and the desirable turf. The Brown Brush Monitor does not use the height differential and rather combines mowing and herbicide treatment in a single pass. The Burch Wet Blade and Weed Bug may offer a solution to broomsedge control in centipedegrass, however no data is currently available either supporting or opposing this claim.
With increased use of PGRs on roadside for reducing maintenance inputs and mowing cycles, application placement technologies may also prove beneficial. Application of PGRs through application placement technologies would not rely on a height differential and rather on a uniform coverage of the PGR on the desired turf grass species. Again broadcast applications of selected PGRs have been shown to significantly reduce maintenance costs. Also, with the limited amount of knowledge currently available about these systems, the potential exists for additional savings if more pesticide is absorbed into the plant through the cut surface as opposed to a broadcast application where the PGR is applied and environmental conditions, weather conditions, etc. may inhibit uptake and translocation.
The primary objectives of the research study are to:Compare the Burch Wet Blade and the Weed Bug for broomsedge control in centipedegrass rights-of-way. These technologies will be compared to a wick application.Compare the Burch Wet Blade, the Weed Bug, and the Brown Brush Monitor for PGR application in bahiagrass and tall fescue rights-of-ways. These technologies will be compared to a broadcast application, which is standard practice.
The outcome of the proposed research will determine if application placement technologies offer a viable solution to the particular problem of broomsedge contamination in centipedegrass rights-of-way as well as PGR application enhancement. If the evaluated technologies do prove useful, benefits include immediate enhancement of roadside aesthetics through the removal of broomsedge, a weed species, as well as more uniform and lower growing turf resulting from PGR applications.
In summary, the ultimate research products will become a component of an integrated roadside vegetation management program in North Carolina. Additionally, research results may impact vegetation management throughout the United States."
