According to the Federal Highway Administration, there are approximately 4.1 million miles of paved and unpaved public roads in the United States — all requiring some level of roadside management. This vast amount of roadside acreage provides a constant challenge to roadside vegetation managers, and, as this acreage has grown over the years, new tools and techniques have been developed to control vegetation along these areas.
The early days
All photos courtesy of Lloyd Hipkins, VA Tech.Early efforts to manage roadside vegetation involved manual methods of cutting, pulling and tilling plants, along with biological methods of allowing sheep and other grazing animals to keep grasses, brush and palatable shrubs under control. Other efforts revolved around maintaining roadside areas with dense, desirable vegetation that would provide a natural resistance to invasive or undesirable plants, or even altering soil pH levels, salinity or fertility levels to control weeds.
Lloyd Hipkins, extension weed specialist with Virginia Tech, has been presenting the history of roadside vegetation for more than 30 years. “In the early 1900s, roadside vegetation management was concerned with two things: trees, because they had the potential to create roadway hazards if they fell; and the impact of vegetation on adjacent land — especially farmland,” said Hipkins. “Back then, counties and states only owned easements, and the farmers wouldn’t give up more than an inch of either side of these easements — so there wasn’t as much area to be managed.”
The development of the national highway and interstate system greatly expanded the roadside area — and the need for and quality of vegetation management required in these areas increased. Of paramount concern is safety. Effective roadside vegetation management improves motorists’ safety by controlling encroaching weeds and brush that can conceal road signs or hide wildlife about to dart into oncoming traffic. Vegetation management also keeps plants from growing in the roadway, which promotes cracking or buckling road surfaces. Environmental quality issues along roadsides include erosion control, stormwater management, protection of wildlife habitat and control of noxious and invasive weeds.
Herbicides enter the picture
The advent of herbicides gave roadside managers a highly effective way to control vegetation and keep roads safer and more environmentally sound. As early as ancient Rome, naturally occurring herbicides like salt and ashes were used to control vegetation. In the late 1800s, copper sulfate was used as a weed-control agent. In the early to mid-1900s, sodium arsenite solutions were used as herbicides. “Sodium borate also was used primarily in the Midwest for noxious weeds — mostly knapweed — that were encroaching on neighboring cropland,” Hipkins added.
In the 1940s, several synthetic herbicides became available. The first widely used synthetic herbicide was 2,4-dichlorophenoxyacetic acid, commonly referred to as 2,4-D. In fact, because it’s so effective, it remains one of the most commonly used herbicides in the world.
“In the early 1940s, there weren’t any products that were marketed specifically as herbicides,” said Hipkins. “Then, around this time, 2,4-D was found to be very effective at controlling broadleaf plants, and it really became the first widely used herbicide.” But 2,4-D has its limitations, especially in the roadside environment.
Herbicide formulations have evolved greatly over time, both in terms of selectivity and environmental characteristics, based upon the needs of vegetation managers, sites surrounding application sites and the demands of the public. For example, in 2005, Dow AgroSciences introduced aminopyralid as the active ingredient in Milestone VM specialty herbicide, which provides low use rates, residual control and safety to most cool- and warm-season grasses.
Advances in methods and equipment
Today, maintenance of the nation’s roadsides requires ongoing program and equipment upgrades to increase efficiency while improving safety. This may translate to choosing herbicides that require fewer pounds of active ingredient, while offering greater efficacy and more favorable environmental attributes. For example, in the 1950s, borate herbicides (polybor-chlorate) were applied at rates of up to 3,200 pounds per acre in an attempt to keep areas vegetation-free for one year. Some new herbicides may be applied at rates as low as 0.5 ounce of product per acre. The introduction of diluents and surfactants — additives to the herbicide mix — has aided efficacy.
In addition, many of the herbicides used today provide targeted control of undesirable species while giving vegetation managers the flexibility to better manage desirable grasses and forbs, as well as adjacent vegetation.
Parallel to the automobile becoming the preferred method of transportation, and roads developing into interstates, roadside management equipment has been improved to keep up. Today, most herbicides are applied as water-based sprays by using ground equipment such as mounted, towed and hand-held sprayers.
“Fifty years ago, roadside vegetation crews used common agricultural equipment to apply herbicides,” said Hipkins. “Now, high-end, sole-purpose equipment has features like self-adjusting radars that help applicators maintain a constant speed, injection systems to handle all the mixing, and GPS systems that can store data such as which herbicides were used where and in what quantities.”
Because chemical and mechanical management methods play major roles in controlling brush and weeds, the technology has evolved to produce equipment that combines mowing and herbicide applications. “Some combination mowing systems are designed to mow and treat with herbicides in one pass and provide several benefits, including reduced stem densities and separate mowing and application chambers for increased effectiveness,” said Hipkins. “Other systems employ a process that keeps the cutting blade wet with herbicide as it cuts.”
Another advancement with herbicide applications is the development of returnable, refillable container systems, such as the Continuum Prescription Control & Container Management System. It relieves roadside vegetation managers of several responsibilities, including the rinsing, storing and disposing of herbicide containers. Such systems can increase worker safety due to reduced herbicide exposure, while also reducing labor and inventory costs. In addition, these systems encourage sound environmental stewardship with returnable, refillable containers.
Scientific discovery and technological advancement will continue to provide updated equipment, products and application techniques for roadside vegetation management.
Article provided by Dow AgroSciences (www.vegetationmanagement.com) — reprinted by permission.
When treating areas in and around roadside or utility rights-of-way that are or will be grazed or planted to forage, important label precautions apply regarding harvesting hay from treated sites, using manure from animals grazing on treated areas or rotating the treated area to sensitive crops. See the Milestone VM product label for details.
Always read and follow label instructions.