Alternative Management of Roadside Vegetation

Management of vegetation is an important element of roadside maintenance for safety and aesthetics. Current methods of management by highway departments principally involve mowing and the use of conventional, chemical herbicides. This research addressed use of herbicides (citric acid, clove oil, corn gluten meal, and pelargonic acid) that are considered as alternatives to conventional herbicides and the use of mechanical treatments of woodchip and bark mulches and burning. These alternative methods were compared with the use of conventional herbicides to assess the relative efficacy of treatments on roadside sites. A single application of pelargonic acid demonstrated immediate or short-term suppression of growth of vegetation; however, the efficacy lasted for no more than 6 weeks, after which regrowth was not distinguishable from untreated vegetation. Repeated applications of pelargonic acid will be necessary for season-long efficacy. Formulations of citric-acetic acid gave no control or only weak suppression of vegetative growth soon after application, and no suppression was evident after 6 weeks, suggesting that these materials have only limited use in roadside environments. The effects of burning lasted for about 6 weeks. No suppression of growth of roadside vegetation occurred with the use of corn gluten meal, which acted as a nitrogen fertilizer to promote growth. Mulches of bark or woodchips were strongly suppressive against emerging vegetation for 2 years, but were more effective in the first year than in the second year after application. The costs of materials and labor for the alternative practices were substantially more than for the conventional herbicides used in this study.