Herbicide Alternatives Research - Executive Office of Transportation

Vermont has tested the use of allelopathic plants at selected sites (Personal communication with
Craig Dusablon, Landscape Coordinator, Vermont Agency of Transportation). The plants
selected were cultivars of sheep fescue (Festuca ovina L.), chewings fescue, and hard fescue
(Festuca longifolia Thuill.). Results were reported as being disappointing in that little effect was
imparted on other vegetation by these grasses.
2.3.4 Biological Control
Biological Agents. Certain biological agents may be used to manage roadside vegetation,
particularly where broad-scale herbicide application is neither practical nor desirable. Biological
control agents include host-specific insects but might also involve the use of fungi, such as rusts
and other plant pathogens that weaken plants by infecting plant foliage. Daar and King (1997)
provide a partial list of biological agents for managing specific weeds, some of which are
common to Massachusetts roadways. Additional information on weed feeding insects is
available on the Cornell University website:
http://www.nysaes.cornell.edu/ent/biocontrol/weedfeeders/wdfdrtoc.html
2.3.5 Chemical Control
Natural herbicides. A number of weed killers are derived or have originated from natural
sources and may offer an alternative to synthetic chemicals. Among these Finale
(phosphinothricin; glufosinate-ammonium, Hoechst-Roussell Agri-Vet Company, Sommerville,
N.J.), Scythe (pelargonic acid, Mycogen Corporation, San Diego, Calif.), Burn-Out (acetic acid;
Burnout II has acetic acid, clove oil, citric acid, and other ingredients; St. Gabriel Laboratories,
Gainesville, Va.), and corn gluten meal (Nowak 2003). These may be used for spot treatment of
weeds or broadcast application. All are nonselective herbicides that kill topgrowth and are
meant mainly for early season application.
Young (2003) reported on a series of experiments and field trials using natural herbicides for
roadside vegetation control in California. Experiments included the materials listed in the table
below. Of the materials tested, only coconut oil, a fatty acid, and an experimental material
consisting of plant essential oils provided post emergent weed control comparable to that of
glyphosate. However, when costs were taken into consideration, these alternative materials far
more expensive than traditonal chemicals due to the concentrations and number of applications
required.
Plant Growth Regulators. A number of plant growth-regulating chemicals are available for use
in vegetation management (Liskey 2004). The use of growth-suppressing agents, which may be
classed also as chemical herbicides, has been or is currently in use as a means of reducing the
frequency and, therefore, cost of roadside vegetation management. Pennsylvania DOT has been
using a combination of Embark (mefluidide, 3M Company, St. Paul, Minne.) plus Escort
(metsulfuron, du Pont, Wilmington, Del.) at 6 oz plus 0.25 oz/acre to treat grass areas of tall
fescue (Festuca arundinacea Schreb.) (Gover et al., 2002). Experimental work at the
Pennsylvania State University (Gover et al., 2002) also has demonstrated effective suppression
of turf with Embark plus Telar (chlorsulfuron, du Pont, Wilmington, Del.) or Event (imazethapyr
and imazapyr, ammonium salts of derivatives of pyridinecarboxylic acid; American Cyanamide
Company, Wayne, N.J.). Johnson et al. (1996) concluded that a combination of Embark with
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