Roadside revegetation and roadside landscaping with native species have increased over the past decade because of growing environmental awareness, recent plant material availability (Knapp and Rice, 1994), and active promotion by the Federal Highway Administration (Harper-Lore, 1996; Steinfeld et al., 2007). In Hawaii, the use of native species on roadsides is a relatively new endeavor (Baldos et al., 2010). Roadside establishment and seed production protocols are currently being developed for several native groundcovers and shrubs. Tropical fimbry (mau‘u ‘aki‘aki in Hawaiian) is one of several native groundcover species considered by the Hawaii Department of Transportation for roadside revegetation.
Tropical fimbry is a tuft growing perennial sedge with short rhizomes and stiff, leathery leaves. It is indigenous to the coastal areas of the Pacific basin, including Australia, western Malesia, Pacific Islands, and the Neotropics (Wagner et al., 1999). In Hawaii, it is commonly found growing on sandy beaches and rocky outcrops close to the ocean.
Certain characteristics of tropical fimbry make it a potential native groundcover for roadsides and landscapes. Its unusual leaf texture and similarity in growth with dwarf mondograss (Ophiopogon japonicus) make it highly ornamental. In fact, it has been used as a native groundcover for commercial, residential, and resort landscapes in Hawaii. Besides its unique form, tropical fimbry also possesses salt, wind, and drought tolerance. Propagation of this species can be easily done using seeds. Its small seed size make it amenable to hydroseeding (Baldos, 2009).
Because of its compact size and relatively slow growth, successful roadside establishment of tropical fimbry will require safe and effective weed control methods. Providing a weed-free environment during early establishment is essential for this native sedge to persist and exclude future weed invasions. To develop a weed management protocol specific to this species, safe and effective pre- and postemergence herbicides labeled for roadside use need to be identified. The studies in this preliminary and regional report characterized the response of tropical fimbry to the preemergence herbicides, oryzalin and oxadiazon, and to the postemergence herbicides, carfentrazone-ethyl + MCPA + mecoprop + dicamba, carfentrazone-ethyl + 2,4-D + mecoprop + dicamba, aminopyralid, and sulfosulfuron.
Oryzalin is a soil applied preemergence herbicide that is labeled for use on nonbearing fruit and nut crops, vineyards, rights-of-way areas such as roadsides as well as in Christmas tree plantations and landscape nurseries (Senseman, 2007). It controls many annual grasses and broadleaf weeds, including barnyardgrass (Echinochloa crus-galli), crowfootgrass (Dactyloctenium aegyptium), junglerice (Echinochloa colona), goosegrass (Eleusine indica), common purslane (Portulaca oleracea), and puncturevine (Tribulus terrestris) (United Phosphorus, 2004). Oxadiazon is another soil applied preemergence herbicide labeled for use in established and newly established turf as well as various ornamental crops (Senseman, 2007). It controls many annual broadleaf and grassy weeds, including sowthistle (Sonchus sp.), creeping woodsorrel (Oxalis corniculata), and goosegrass (Bayer Crop Science, 2002).
Carfentrazone-ethyl + MCPA + mecoprop + dicamba, carfentrazone-ethyl + 2,4-D + mecoprop + dicamba, aminopyralid, and sulfosulfuron are selective postemergence herbicides that mainly control broadleaf weeds. Carfentrazone-ethyl + MCPA + mecoprop + dicamba is a herbicide formulation also known under the registered tradename, Powerzone® (PBI/Gordon Corp., Kansas City, MO). It is especially formulated for broadleaf weed control in warm and cool season turf in institutional, ornamental, and residential areas as well as commercial sod production sites and noncropland sites such as roadsides (PBI/Gordon Corp., 2008). Broadleaf weeds controlled by the said formulation include beggarticks (Bidens sp.), broadleaf plantain (Plantago major), buckhorn plantain (Plantago lanceolata), creeping woodsorrel, and puncturevine. Carfentrazone-ethyl + 2,4-D + mecoprop + dicamba is another postemergence broadleaf herbicide formulation specifically developed for turf. It is registered under the tradename, Speedzone® (PBI/Gordon Corp.). Areas for use and species controlled by Speedzone® are similar to Powerzone®. The main difference between the two carfentrazone-based formulations is the type and amount of the second a.i. [i.e. Speedzone® contains MCPA, while Powerzone® contains 2,4-D]. Aminopyralid is a postemergence herbicide specifically used for broadleaf weed control in rice (Oryza sativa), wheat (Triticum sp.), oil palm (Elaeis guineensis), and rubber (Hevea brasiliensis) as well as in natural areas, rangelands, permanent grass pastures, and industrial vegetation management areas such as roadsides (Senseman, 2007). Weed species controlled by aminopyralid include spiny amaranth (Amaranthus spinosus), beggarticks, and flaxleaf fleabane (Conyza bonariensis) (Dow AgroSciences, 2008). Besides functioning as a postemergence herbicide, aminopyralid also has some preemergence activity on these weed species. Sulfosulfuron is a selective postemergence herbicide that controls many broadleaf weeds (Senseman, 2007) as well as sedge species such as green kyllinga (Kyllinga brevifolia), purple nutsedge (Cyperus rotundus), and yellow nutsedge (Cyperus esculentus) (Monsanto, 2008). It is labeled for use in several cool and warm season turfgrasses as well as some warm season native grasses (Senseman, 2007).
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