Urochloa Mutica) Sushila Chaudhari, B

J. Aquat. Plant Manage. 50: 39-45 Integrating chemical and cultural practices to control para grass (Urochloa mutica) SUSHILA CHAUDHARI, B. A. SELLERS, S. V. ROCKWOOD, J. A. FERRELL, G. E. MACDONALD, AND K. E. KENWORTHY* ABSTRACT ic or environmental harm or harm to human health” (NISC 2006). Approximately 5000 plant species have escaped and Nonnative para grass (Urochloa mutica [Forsk.] T.Q. Nguy- now exist in natural ecosystems in the United States, com- en) is no longer used as forage and has invaded Florida wet- pared with nearly 17,000 species of native plants (Morse et lands. This perennial grass out-competes native vegetation and al. 1995). These invasive species have been identified as one grows into monotypic swards, resulting in unsuitable wildlife of the major threats to ecosystem function and biodiversity habitat. The goal of this research was to improve wetland eco- through competition, suppression, and displacement of na- system health by reducing para grass invasions via an integrat- tive species (Wilcove et al. 1998). Approximately 42% of the ed approach using cultural and herbicide inputs. Experiments animals and plants listed as threatened or endangered under were conducted to determine herbicide efficacy on para grass the Endangered Species Act are at risk, primarily because of under different water depths in combination with burning competition with invasive species (Wilcove et al. 1998). followed by flooding. Herbicides were applied in late fall, fol- The invasion and rapid spread of exotic plant species poses lowed by burning and flooding in early summer. At 1 month a serious threat for native flora and fauna of Florida’s natural after treatment (MAT), all rates of imazapyr and glyphosate areas. Wunderlin and Hansen (2011) reported 1401 exotic provided similar levels of control ranging from 70 to 88% and plant species are currently present in Florida. Of these, 71 91 to 95%, respectively, regardless of the initial water level. species are considered to be highly invasive, or category 1, in Burning followed by immediate flooding reduced the initial natural areas because they are disruptive to native plant com- para grass ground cover in the nontreated checks by at least munity structure and function (FLEPPC 2009). Para grass 62% at 12 MAT, which was 8 months after burning and flood- is listed as a category 1 plant in central and south Florida ing (MAB-F). Reestablishment of native species was similar in (FLEPPC 2009). all plots. Stolon and crown tissues were sampled at monthly in- Para grass is a C4 perennial grass native to Africa that was tervals for 2 years and analyzed for total nonstructural carbohy- introduced to the United States through Brazil (Hitchcock drate (TNC) concentrations. Carbohydrate concentrations in and Chase 1951). It was introduced into Florida in the 1870s stolon and crown tissues were typically lowest in the late winter (Austin 1978) and was recommended as a forage by the Flor- and early spring but increased from May through September. ida Agricultural Experiment Station in 1910 (Mislevy and Therefore, para grass may be more susceptible to herbicide ap- Quesenberry 1999). Para grass was later used in World War II plications in early summer when herbicide will be transported as camouflage around military installations in south Florida with carbohydrates to reproductive tissues. These data indi- (Austin 1978). It can be distinguished from other grass spe- cate that excellent control of para grass can be obtained with cies by the presence of swollen nodes with dense hairs and a fall applications of 1.12 kg ai/ha glyphosate or 0.86 kg ai/ha ligule consisting of a row of short, stiff hairs. Para grass is a imazapyr in combination with early summer burning followed prolific seed producer (>10,000 seeds per square meter) with by flooding. However, an early- to mid-summer application of poor seed viability (Wesley-Smith 1973). Therefore, spread glyphosate and imazapyr may be more effective for areas where and invasion of para grass can mostly be attributed to its sto- flooding cannot be controlled. loniferous growth habit (Langeland and Burks 1998). Key Words: burning, invasive grass, flooding,Urochloas mu- While once widely distributed as a forage grass in most tica, wetlands. tropical and subtropical areas, para grass is now considered INTRODUCTION a serious weed world-wide. It is reported as an agricultural pest in 23 crops in 34 countries, including the United States An invasive species is defined as “a species that is non-na- (Holm et al. 1977). As early as 1921, it was postulated that tive to the ecosystem that causes, or is likely to cause, econom- para grass could be problematic in areas that remain wet (Briggs 1921). Para grass prefers sites that are wet nearly year- *First and second authors: Graduate Assistant and Associate Professor of round and can survive in standing water; invasion is common Agronomy, University of Florida-Institute of Food and Agricultural Sciences, along the edges of canals, streams, creeks, rivers, and other Range Cattle Research and Education Center, 3401 Experiment Station, Ona, FL 33865; Third author: Wetland Habitat Specialist, Florida Fish and wetland ecosystems (Masterson 2007). Wildlife Conservation Commission, T. M. Goodwin Waterfowl Management These aquatic ecosystems provide diverse habitat for wa- Area, 3200 T. M. Goodwin Road, Fellsmere, FL 32948; Fourth, fifth and sixth terfowl by providing a forage base, breeding and nesting authors: Associate Professor of Agronomy, Professor of Agronomy, and As- habitat, cover from predators, and habitat for social interac- sociate Professor of Agronomy, University of Florida- Institute of Food and tions (Murkin et al. 1997). In Florida, T. M. Goodwin Wa- Agricultural Sciences, Agronomy Department, PO Box 110500, Gainesville, FL 32611. Corresponding author’s E-mail: [email protected]. Received for terfowl Management Area (TMGWMA) is a 1570 ha fresh publication April 8, 2011 and in revised form January 19, 2012. water restoration project that began in 1988. Historically a J. Aquat. Plant Manage. 50: 2012. 39 floodplain marsh, the area was diked and drained in 1950s range of moisture conditions and grow very well in water and later managed for agricultural purposes including citrus, up to 1 m deep (Holm et al. 1977). While it seems that pre- sod, and cattle production (Anonymous 2004). Improved scribed burning or flooding has no impact on long-term pastures of flood-tolerant grass species like torpedo grass para grass control, little to no information exists concern- (Panicum repens L.), limpograss (Hemarthria altissima [Poir.] ing the effect of burning followed by flooding in conjunc- Stapf & C.E. Hubb), West Indian marsh grass (Hymenachne tion with herbicides on para grass control. amplexicaulis [Rudge] Nees), and para grass were used for One of the most important decisions when integrating cattle production. Ranchers preferred these grasses because herbicides into a pest management strategy for perennial the area was subjected to frequent flooding during the grasses is application timing. Knowledge of the seasonal rainy season. Drainage for agricultural purposes destroyed variation of total nonstructural carbohydrate (TNC) re- valuable wetlands, increased flood peaks, decreased water serves in para grass tissues may aid in determining the prop- supplies, and created water quality problems (Campbell et er herbicide application timing. Carbohydrate reserves are al. 1984). Since 1988, the Florida Fish and Wildlife Con- important in perennial plants for winter survival, initiation servation Commission (FWC) has managed the property of early spring growth, and to initiate regrowth after herb- for multiple uses, including stormwater retention to re- age removal (White 1973). Kalmbacher et al. (1993) re- duce freshwater discharge into the Indian River Lagoon ported 40% higher wax myrtle mortality when 1.12 kg/ha to restore high quality wetland habitat for waterfowl and triclopyr was applied in late summer (Sep) as compared to to establish a public recreation area. Restoration efforts spring (Mar); the authors suggested that increased move- established ten 61 ha wetland impoundments on the south ment of carbohydrates to the root tissues in summer also end of TMGWMA to provide waterfowl habitat (Anony- increased herbicide translocation toward root tissues. mous 2004). Therefore, the objectives of this research were to (1) Vegetation management at TMGWMA is accomplished test herbicide efficacy in natural areas under different wa- through various techniques such as manipulation of water ter regimes integrated with burning and flooding for para level, mechanical manipulation (e.g., disking and roller grass control, and (2) evaluate total nonstructural carbo- chopping), prescribed burning, mowing, and herbicide hydrate concentration in para grass crown and stolon tis- applications (Anonymous 2004). However, improper im- sues to determine the time-frame for the most efficacious plementation of management techniques such as disking, herbicide applications. roller chopping, and water level manipulation may have increased the spread of para grass in TMGWMA. Cur- MATERIALS AND METHODS rently, it is estimated that approximately 60 to 70% of the impoundments are infested with para grass (S. Rockwood, Field studies Wetland Habitat Specialist, Florida Fish and Wildlife Con- servation Commission, pers. comm.). Large infestations of Experiments were initiated in December 2008 at TMGW- para grass in TMGWMA are reducing the

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