Currently the Indiana Department of Highways is responsible for vegetation management on about 100,000 acres of roadside that receives at least one full cycle of mowing and includes other areas, such as medians and corridors adjacent to traffic lanes, that are mowed twice or three times. Both force-account and contract means are used at a total cost of $3,250,000/year. As an alternative to mechanical mowing, a program of chemical mowing was implemented for the state of Indiana in 1983 with 3 consecutive years of success with use on Interstate and dual-lane roads. Using a combination of primary growth retardant, costreducing additive, surfactant (detergent) to enhance penetration and primary broadleaf herbicide, a single spray application in the spring controls weeds, prevents seedhead formation, and retards growth of grass blades so that no further spraying or mechanical mowing is required for full-season vegetation management. By employing cost-saving combinations of material, costs are equal to or slightly higher than the per acre cost of a single mowing cycle. This program was designed primarily for use on tall fescue-bluegrass mixed turf and resulted in both seedhead suppression and weed control in excess of 90 percent. Those few seedheads that do form are short and do not appear unsightly. Weeds that remain are largely resistant perennials (common milkweed, Canada thistle, and horse nettle) and late-germinating annuals (black medic, upright spurge, common ragweed, wild lettuce, and various foxtails). Grass heights at the end of the growing season remain well within the standards (12 to 18 in.) of the state of Indiana to eliminate any need for mechanical mowing.

Current safety and esthetic standards require that roadsides be mowed. In Indiana, costs are between $20 and $25/acre for one mowing cycle; one to three cycles are required per growing season to establish and maintain adequate sight distances and visual appearances of tall fescue-bluegrass mixed stands. On the basis of research initiated in 1977 at Purdue University (1), a program of chemical mowing was initiated in the state of Indiana in 1983 as an alternative to mechanical mowing (2-3). The requirements were for a single spray application, effective in preventing growth and seedhead formation in bluegrass and fescue. There should be no damage to roots or weakening of turf and no carryover that would limit repeated use on an annual basis. The treatment should be environmentally safe and should control the majority of turf weed species. In addition, the treatment must be cost effective. These various criteria have been met by employing a combination of materials that, when applied together, yield cost effective, full-season vegetation management.