Fire Effects Information System (FEIS)

FEIS Home Page

Panicum repens

• INTRODUCTORY
• DISTRIBUTION AND OCCURRENCE
• BOTANICAL AND ECOLOGICAL CHARACTERISTICS
• FIRE EFFECTS AND MANAGEMENT
• MANAGEMENT CONSIDERATIONS
• APPENDIX: FIRE REGIME TABLE
• REFERENCES

INTRODUCTORY

AUTHORSHIP AND CITATION FEIS ABBREVIATION NRCS PLANT CODE COMMON NAMES TAXONOMY SYNONYMS LIFE FORM
	Photo by Forest & Kim Starr, Starr Environmental, Bugwood.org

AUTHORSHIP AND CITATION:
Stone, Katharine R. 2011. Panicum repens. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://www.fs.usda.gov /database/feis/plants/graminoid/panrep/all.html [].

FEIS ABBREVIATION:
PANREP

NRCS PLANT CODE [102]:
PARE3

COMMON NAMES:
torpedo grass
couch panicum
dog-tooth grass
torpedograss

TAXONOMY:
The scientific name of torpedo grass is Panicum repens L. (Poaceae) [2,24,40,43,58,87,104,112,114,115].

SYNONYMS:
None

LIFE FORM:
Graminoid

DISTRIBUTION AND OCCURRENCE

• GENERAL DISTRIBUTION
• HABITAT TYPES AND PLANT COMMUNITIES

GENERAL DISTRIBUTION:
Torpedo grass is native to both the Old and New Worlds [44], with reported sources of origin including southern Europe [105], the Mediterranean, the Arabian Peninsula, Israel [29], northern [29], tropical, and southern Africa [29,105], Argentina [29], and Australia [29,109].

Torpedo grass was introduced to the Gulf Coast of the United States sometime prior to 1876, when it was first collected in Alabama [65]. It was introduced in seed for forage crops [65,69]. Seed may also have been transported via ballast from sailing vessels carrying lumber from the Mediterranean [109]. In the early 1900s the United States Department of Agriculture imported and distributed torpedo grass seed to provide forage for cattle [69]. By 1950, it was planted in nearly every southern Florida county and in a few central and north-central counties [65]. It subsequently escaped cultivation [29].

As of this writing (2011), torpedo grass occurs in tropical and subtropical regions throughout the world from latitude 35 °S to 43 °N [49]. In the United States, the distribution of torpedo grass is limited to the southern Atlantic coast from North Carolina south and west to Texas, and isolated populations in California and Hawaii [58]. It also occurs in Mexico [11]. Plants Database provides a distributional map of torpedo grass.

HABITAT TYPES AND PLANT COMMUNITIES:
Torpedo grass occurs in both aquatic and terrestrial plant communities [44], including coastal sand, wetland, and forested plant communities.

Coastal sand plant communities: Torpedo grass establishes in coastal sand plant communities around the Gulf of Mexico, including sand dunes [11,67,68,74,77,81], ridges [67], plains [11], and beaches [68]. Torpedo grass occurred in coastal dune communities along the northern Gulf Coast including Texas, Mississippi, Louisiana and the west coast of Florida. Common associates included turtleweed (Batis maritima), saltgrass (Distichlis spicata), marsh fimbry (Fimbristylis castanea), largeleaf pennywort (Hydrocotyle bonariensis), and dwarf saltwort (Salicornia bigelovii) [77]. On a barrier island between the Mississippi Sound and the Gulf of Mexico, torpedo grass occurred on sand dunes dominated by seaoats (Uniola paniculata), moist dunes with Le Conte's flatsedge (Cyperus lecontei) and largeleaf pennywort, and in a coastal sand frostweed-woody goldenrod (Helianthemum arenicola-Chrysoma pauciflosculosa) plant community [81]. On an island off the coast of Louisiana, torpedo grass established on sandy, compacted turf with erect centella (Centella erecta) and starrush whitetop (Rhynchospora colorata) [10]. Herbarium records from Texas documented torpedo grass occurring between a seawall and saltgrass flats [36]. In coastal areas of Mexico, torpedo grass occurred on sand dunes and sandy plains with slender grama (Bouteloua repens), sideoats grama (B. curtipendula), Acapulco grass (B. dimorpha), bahiagrass (Paspalum notatum), hilograss (P. conjugatum), and mesosetum grasses (Mesosetum spp.) [11].

Wetlands and riparian areas: Torpedo grass establishes in a variety of moist plant communities, including wetlands [13,17,18,30,35,36,76,80,84,113], wet prairies [24,33,34,61,73,113], and in or around water bodies [29,88,93,113].

Wetlands: In Gulf Coast freshwater marshes, torpedo grass occurred with alligatorweed (Alternanthera philoxeroides), herb of grace (Bacopa monnieri), fragrant flatsedge (Cyperus odoratus), common water hyacinth (Eichhornia crassipes), spikerush (Eleocharis sp.), hydrocotyle (Hydrocotyle sp.), sprangletop (Leptochloa sp.), maidencane (Panicum hemitomon), common reed (Phragmites australis), bulltongue arrowhead (Sagittaria lancifolia ssp. media), saltmeadow cordgrass (Spartina patens), cattail (Typha sp.), hairypod cowpea (Vigna repens), and giant cutgrass (Zizaniopsis miliacea) [30]. On a barrier island in the Gulf Islands National Seashore, Florida, torpedo grass occurred in freshwater marshes with southern umbrella-sedge (Fuirena scirpoidea) and broomsedge bluestem (Andropogon virginicus) [76]. In Florida, torpedo grass dominated part of a 1-year-old wetland constructed for wastewater treatment but 2 years later had been replaced by pickerelweed (Pontederia cordata), bulltongue arrowhead, and Olney's threesquare bulrush [13]. In southwestern peninsular Florida, torpedo grass was an occasional species in disturbed wet areas and seasonal ponds and sloughs occurring within dry prairies with saw-palmetto (Serenoa repens); in South Florida slash pine (Pinus elliottii var. densa) flatwoods; and in river-corridor hammocks with live oak (Quercus virginiana), laurel oak (Q. laurifolia), and cabbage palmetto (Sabal palmetto) [55].

On the Mississippi River delta, torpedo grass occurred in coastal marsh plant communities containing mixtures of common reed [17,18,84], saltmeadow cordgrass [17], smooth cordgrass (S. alterniflora), cattails (Typha spp.), Olney's threesquare bulrush (Schoenoplectus americanus), and giant cutgrass [84]. In the same region, torpedo grass occurred on mud flats with giant cutgrass, seacoast bulrush (Bolboschoenus robustus), smooth cordgrass, and narrow-leaved cattail (Typha angustifolia) [72]. In southeastern Louisiana, torpedo grass occurred in thick-mat floating-marsh plant communities. Species composition varied, but these communities contained monocultures or mixtures of bulltongue arrowhead (Sagittaria lancifolia), cattails, Olney's threesquare bulrush, cordgrass (Spartina spp.), giant cutgrass, and common reed [80]. Herbarium records from Texas documented torpedo grass occurring in a small freshwater marsh with spadeleaf (Centella asiatica), jointed flatsedge (Cyperus articulatus), tapertip flatsedge (C. acuminatus), velvet panicum (Dichanthelium scoparium), Virginia buttonweed (Diodia virginiana), and mountain spikerush (Eleocharis montana) [36].

Wet prairies: In southeastern Florida, torpedo grass occurred in wet prairies characterized by St. Johnswort (Hypericum spp.), yelloweyed grass (Xyris spp.), spadeleaf, rush (Juncus spp.), panicgrass (Panicum spp.), and Tracy's beaksedge (Rhynchospora tracyi) [73]. Torpedo grass occurred infrequently and at low cover in wet prairies in west-central Florida. Common species included dwarf crabgrass (Digitaria serotina), broadleaf carpetgrass (Axonopus compressus), knotgrass (Paspalum distichum), and pineland threeawn (Aristida stricta) [24]. In southwestern Louisiana, torpedo grass occurred in plant communities of intermixed prairie and cheniere (ridges made of shell fragments and sand that rise above sea level in coastal marshes). Species commonly found in prairies included golden tickseed (Coreopsis tinctoria), rosy camphorweed (Pluchea rosea), blackeyed Susan (Rudbeckia hirta var.pulcherrima), marsh flatsedge (Cyperus pseudovegetus), keeled bulrush (Isolepis koilolepis), slickseed fuzzybean (Strophostyles leiosperma), tapertip rush (Juncus acuminatus), forked rush (J. dichotomus), gaping grass (Panicum hians), brownseed paspalum (Paspalum plicatulum), and prairie wedgescale (Sphenopholis obtusata). Common species on chenieres included live oak, sugarberry (Celtis laevigata), and Hercules' club (Zanthoxylum clava-herculis) [34]. Torpedo grass occurred in smooth cordgrass prairies along the Mississippi River delta [33] and in Louisiana and Texas [33,61].

In or around water bodies: In and around Lake Okeechobee in Florida, torpedo grass established with Gulf Coast spikerush (Eleocharis cellulosa), American white waterlily (Nymphaea odorata) [93], and little sand cordgrass (Spartina bakeri) [29]. Herbarium records from Florida documented torpedo grass occurring in and around a pond with Spanish needles (Bidens bipinnata), shortleaf spikesedge (Kyllinga brevifolia), taperleaf water horehound (Lycopus rubellus), and baldcypress (Taxodium distichum) [113]. Torpedo grass occurred in a disturbed shoreline plant community in southeastern Alabama. The shoreline plant community contained yellowfruit sedge (Carex annectens) and southern waxy sedge (C. glaucescens). Woody species included wax-myrtle (Myrica cerifera) and black tupelo (Nyssa sylvatica) [88].

Forested plant communities: Torpedo grass establishes in some areas with a tree canopy. Herbarium records from Florida documented torpedo grass occurring along a road in sand pine (Pinus clausa) scrub and in slightly disturbed areas in white sand scrub associated with coastal plain honeycombhead (Balduina angustifolia), blue maidencane (Amphicarpum muhlenbergianum), lopsided Indiangrass (Sorghastrum secundum), jeweled blue-eyed grass (Sisyrinchium xerophyllum); in oak (Quercus) woods, and in pinelands with cabbage palmetto, serenoa (Serenoa), and sweetgale (Myrica) [113]. At the Cumberland Island National Seashore off the coast of southern Georgia, torpedo grass was restricted to open areas along roads bisecting maritime hammocks and pine (Pinus)-oak forests. Live oak dominated maritime hammocks, while loblolly pine (Pinus taeda), slash pine (P. elliottii), longleaf pine (P. palustris), and live oak occurred in pine-oak forest [116]. On a barrier island between the Mississippi Sound and the Gulf of Mexico, torpedo grass occurred in open forests with slash pine, sand live oak (Q. geminata), and myrtle oak (Q. myrtifolia) [81]. Herbarium records from Texas documented torpedo grass as common in a drainage ditch along the edge of a patch of forest dominated by sugarberry and nonnative Chinese tallow (Triadica sebifera)[36].

BOTANICAL AND ECOLOGICAL CHARACTERISTICS

• GENERAL BOTANICAL CHARACTERISTICS
• SEASONAL DEVELOPMENT
• REGENERATION PROCESSES
• SITE CHARACTERISTICS
• SUCCESSIONAL STATUS

Torpedo grass is a perennial grass growing up to 3 feet (1 m) tall from sturdy, widely creeping or floating rhizomes [65]. Culms are erect or leaning [65]. Leaf sheaths are hairy and leaf blades are stiff, linear, flat, or folded with an often waxy or whitish surface [69]. Inflorescences are loose, open, terminal panicles, 3 to 9 inches (7-22 cm) long, with erect or ascending branches. Spikelets are 2 to 3 mm long and about 1 mm wide [65]. Fruits are lanceolate, straw-colored caryopses [105]. Seeds are 2.2 to 3.1 mm long, white, and smooth [37].

Photo by John D. Byrd, Mississippi State University, Bugwood.org

Torpedo grass has fibrous roots [37], though plants examined on a golf course in southern Florida had few roots [14].

Torpedo grass has both long and short, knotty rhizomes [40]. Rhizomes have a rigid, sharp-pointed tip that gives the plant its name [65]. In wet fields in Sierra Leone, rhizomes formed a mat 6 inches (15 cm) thick [27]. A nonnative plant guide reports that rhizomes may reach lengths of >20 feet (6 m) [105]. Two literature reviews suggest that most torpedo grass rhizomes are found within the top 24 inches (60 cm) of soil, but some may penetrate to 23 feet (7 m) [20,92]. On sand dunes and dry sand ridges in the Mississippi Sound, torpedo grass rhizomes were found to a depth of 30 inches (80 cm) [67]. In field experiments in Japan most rhizome and roots were found in the top 12 inches (30 cm) of the soil, but some extended down to 17 inches (42 cm) [52].

Torpedo grass populations form extensive colonies [40] and may form dense, floating mats where they establish in or adjacent to water [44]. Population expansion may be rapid; in the Lake Okeechobee region, torpedo grass cover increased 21% in 5 years, from 220 acres (89 ha) in 1994 to 264 acres (107 ha) in 1999 [45].

Raunkiaer [86] life form:
Hemicryptophyte
Geophyte
Helophyte

SEASONAL DEVELOPMENT:
A nonnative plant guide suggests that torpedo grass flowers nearly year round [65]. Flowering months range from May to November in Florida [25,43,113,114,115]. Herbarium records from Texas documented it flowering and fruiting in June, July, August, October, and December [36].

Torpedo grass growth may be related to local hydroperiods. In Sierra Leone, torpedo grass rhizomes were dormant while under seasonal floodwater from mid-June to early January. As floodwaters retreated, shoots grew to a height of 3 feet (1 m) in 3 months. Seeds were produced in June [27].

REGENERATION PROCESSES:

Vegetative regeneration appears to be the primary means of torpedo grass establishment and spread [1,37,49,69]. Seed production and viability appear to be limited [1,69].

Vegetative regeneration: Torpedo grass is rhizomatous [14,20,27,40,43,65,105,112], and most reproduction is accomplished via vegetative spread from and fragmentation of rhizomes [49,65,105]. Rhizome sprouting is not limited to apical regions; it can also occur via axillary buds, which are produced along the entire length of the rhizome [82,106,109]. Torpedo grass plants allocate much of their biomass to rhizomes [14,52,109]. On a golf course in southern Florida, rhizomes comprised 87% of total plant biomass [14]. Rhizomes are strong enough to penetrate wood and asphalt [44].

Photo by Karen Brown, University of Florida, Bugwood.org

Regenerative buds are not limited to rhizomes but can also form on tillers [20,40,52,89] and stem fragments. In greenhouse studies in Florida, 1-node stem sections cut from erect shoots and tillers were laid on top of potting soil. Roots appeared from nodes within 1 day of planting, with new shoots arising within 3 to 4 days of planting. After 4 weeks of growth, 79% of tiller segments and 93% of shoot segments had produced new vegetative growth [89].

Torpedo grass rhizome fragments are capable of fast growth. In field experiments in Japan, 1-node rhizome fragments reached 76 inches (192 cm) in length 190 days after planting, with a growth rate as high as 0.5 inches (1.3 cm)/day. One rhizome produced 22,635 nodes in a year [52]. In growth trials in Florida, torpedo grass rhizomes placed in flooded pots and fertilized at a rate of 40 g/330 cm² (17-6-10) increased their dry weight 728-fold over 16 weeks in the summer (0.9 g to 656 g) [96]. In greenhouse growth trials, new shoots of torpedo grass emerged from 1-node rhizome fragments after 21 days. Rhizome production did not begin until after 4 weeks of growth, when plants produced 1 to 3 rhizomes. Tiller production from the primary culm began after 2 weeks of growth. After 16 weeks, approximately 5 "primary" tillers had developed from the primary culm, though numbers were higher at 8 weeks, followed by some tiller death. After 16 weeks of growth, plants averaged 3 to 4 "secondary" tillers arising from primary tillers. Tillers also developed from rhizomes after 4 weeks of growth and were more abundant than tillers arising from the primary culm; after 16 weeks of growth, rhizome tillers averaged approximately 22/plant [20].

The potential for torpedo grass plants to reproduce vegetatively may be related to several factors, including soil depth, plant density, temperature, and moisture.

Results of greenhouse [53,92,107] and field [106] experiments show that torpedo grass rhizome sprouting decreases as burial depth increases. In greenhouse experiments, the emergence of sprouts from 6-node-long torpedo grass rhizomes after 30 days was significantly reduced at burial depths greater than 2 inches (4 cm) (P<0.05), with only 25% of rhizomes sprouting from depths of 6 inches (16 cm) [107]. In field experiments in Florida, sprout emergence was reduced by burying rhizomes at depths >3 inches (8 cm) [106]. After 1 year, 67% of 1-node rhizomes produced shoots when buried at 0.4 inches (1 cm) while no 1-node rhizomes produced shoots when buried at 8 inches (20 cm). No rhizomes with any number of nodes sprouted from burial depths >20 inches (50 cm). Shoots emerged more quickly from rhizomes buried at shallower depths; sprouts from rhizomes buried 2 inches (5 cm) emerged as early as 5 days after burial, while no sprouts from rhizomes buried 12 inches (30cm) emerged until 21 days after burial [53]. Some experiments show that rhizome size (length or number of nodes) increases the potential for rhizomes to sprout at greater depths [53,92].

Plant density may impact torpedo grass tillering, but it may not influence allocation of resources to rhizomes. In greenhouse growth trials, tiller production and tiller dry weight were significantly lower at high (4 plants/pot) versus low (1 plant/pot) density, on both a per pot and per plant basis (P<0.05). Torpedo grass plants at both densities allocated about one-fifth of their dry weights to rhizomes [21].

Torpedo grass rhizome survival and sprouting are limited by extremes of temperature. See Climate for more information on this topic.

Torpedo grass rhizomes can survive both extremely dry and extremely wet conditions. In greenhouse experiments, air-drying 6-node-long torpedo grass rhizomes to 35% to 60% of initial fresh weight had no effect on subsequent growth [107]. In growth chamber experiments in Japan, air-drying rhizomes led to a reduction in bud sprouting but not to an increase in rhizome death [1].

Torpedo grass is tolerant of flooding. In growth trials in Florida, all of the rhizomes (n=64; 3 to 4 buds) tested survived flooding for approximately 4 months [96]. Flooding may or may not induce rhizome dormancy. In Sierra Leone, torpedo grass rhizomes were dormant while under seasonal floodwater from mid-June to early January. Shoots emerged after floodwaters retreated [27]. If rhizomes do sprout in water, their establishment may be limited. Field observations in Florida suggested that fragments of torpedo grass did not readily establish in deep standing water. Once fragments became anchored along shorelines, they established quickly [89]. Experimental pond studies showed that stem and rhizome fragments remained buoyant through 10 weeks of observations. Shoot and root production began within 2 weeks. Both rhizomes and stem fragments produced stems averaging 5.5 inches (13.9 cm) in length by the 10th week of the study. Fragments were unlikely to establish without contact with sediment, however. Stem and root fragments produced roots when inundated at all water depths tested (up to 50 inches (125 cm)), but stem elongation above the water in the 1st 4 weeks of growth was more likely in shallow (<10 inches (25 cm)) than deep water. After 12 weeks, stem fragments planted in shallow water had new stems with an average height of 22 inches (55 cm) above the water line. Only fragments in shallow water initiated rhizome growth. The number and radial spread of rhizomes from the parent plant decreased significantly with water depth (P<0.05). The growth of 15-week-old plants originating from stem fragments declined as water depth increased [93].

Torpedo grass sprouts after herbicide application [14,39,54,59,83,92], grazing [79], cutting, [19,39], plowing or disking [83,92], and burning [45,46,92,98]. Population spread may be accomplished either through the vegetative expansion of existing populations or via the transport of plant fragments along waterways [69], in fill dirt and hay, and attached to boat trailers and machinery [92].

Pollination and breeding system: No information is available on this topic.

Seed production: As of this writing (2011), limited information exists regarding seed production in torpedo grass. Researchers from Japan described torpedo grass as "incapable of fruiting" [52]. A nonnative plant guide reports that seed abundance is variable [65]. Torpedo grass seeds have been found or studied in Spain [26], Mexico [71], Mississippi [107], Sierra Leone [27], and Florida (Smith 1995 personal communication cited in [96]). However, some sources report that seeds are largely unviable. Researchers reported that torpedo grass does not bear fertile seeds in Taiwan [83].

Seed dispersal: As of this writing (2011), little information was available regarding dispersal of torpedo grass seeds. Seeds of torpedo grass were found in fecal pellets of wild spur-thighed tortoises (Testudo graeca) in Spain [26]. Seed viability was not tested.

Seed banking: As of this writing (2011), little information was available regarding seed banking by torpedo grass. Researchers in Florida were unable to germinate torpedo grass seed from the soil seed bank near Lake Okeechobee [93].

Germination: The germination potential of torpedo grass appears to be variable, with some studies reporting low or no seed viability, and others reporting high germination rates. One manager reports that no viable torpedo grass seed was found in Florida (personal communication [6]). In another Florida study, Smith (1995 personal communication cited in [96]) found extremely low germination (1 out of 1,000) of torpedo grass seeds. In a series of laboratory experiments testing the effects of light, temperature, scarification, and chemical stimulation on torpedo grass germination, no fresh-collected seeds from Mississippi germinated [107]. In contrast, a weed identification guide suggests that torpedo grass seeds germinate easily, though they require moisture [37].

In laboratory germination trials, torpedo grass seeds collected from Veracruz, Mexico, had low germination rates when held at constant temperatures. Germination rates were higher when seeds were exposed to fluctuating temperatures. At both temperature regimes, fresh seeds had lower germination rates than those stored for 7 to 14 months.

Germination rates were not affected by light regime, burial depth, or nitrate availability. Seeds were capable of germination under high-salinity conditions, including exposure to 100% sea water [71].

Seedling establishment: As of this writing (2011), little information was available regarding torpedo grass seedling establishment. Establishment via seed has been reported secondhand from Portugal [59,109]. In Sierra Leone, there was no evidence of plants emerging from seed despite documented seed production [27].

Plant growth: Growth of established torpedo grass plants may be influenced by light, nutrient availability, moisture, and temperature (See Climate for more information on this topic). In field experiments, 75% shading significantly reduced dry matter production, leaf area, and height of torpedo grass (P<0.05) [109]. In greenhouse experiments, nitrogen fertilizer significantly increased torpedo grass shoot length, shoot production, and aboveground biomass (P<0.05) [51]. A nonnative species guide for the world reports that plant morphology may vary with soil moisture; torpedo grass growing in dry soils may be short and produce few flowers per panicle, while in moist soils it may grow tall and produce a many-flowered panicle [49].

SITE CHARACTERISTICS:
Torpedo grass tolerates a range of site characteristics. It has documented preferences for a warm climate, sandy soils, and moist conditions [92], though it tolerates other site characteristics.

Site types: In North America, torpedo grass occurs in both aquatic and terrestrial plant communities [44,69]. Floras and herbaria records document torpedo grass on a variety of site types, including disturbed areas [38,43,104,113,114,115] like roadsides [36,43,104,113], along paths [113], in fields [113] or in agricultural areas [43]. Torpedo grass establishes in coastal areas, including coastal swales [25,36,40,115], beaches [40], sand dunes, sand bars, seawalls, island shores [36], tide pools [113], and tidal flats [40,113]. It also occurs along inland waterways, including lakes [40,113,114,115], ponds [36,40,113], canals [40,43,113], ditches [36,40,43,104,113], and moist plant communities, including marshes [25,36,43,113,115], bogs [43], and wet prairies [43,113]. See Habitat Types and Plant Communities for detailed descriptions of plant communities where torpedo grass occurs.

Climate: Torpedo grass is limited to tropical and subtropical climates [40]. Its sensitivity to prolonged cold temperature limits the spread of torpedo grass into upper latitudes or altitudes [7].

In the United States, torpedo grass establishes in subtropical climates such as those found in Florida [55,78], Georgia [116], and Louisiana [34,80]. In west-central peninsular Florida, mean daily maximum temperature ranged from 70.5 °F (21.4 °C) in January to 90.3 °F (32.4 °C) in August. The mean daily minimum temperature ranged from 50.4 °F (10.2 °C) in January to 74.5 °F (23.6 °C) in August [78]. Areas where torpedo grass establishes generally have high annual precipitation.

Torpedo grass may be killed by cold temperatures although it may withstand short exposure to cold. Apical 6-node-long rhizome fragments of torpedo grass died following 24-hour exposure to 23.9 °F (-4.5 °C) but survived exposure to 39.2 °F (4 °C) [108]. Planted torpedo grass rhizomes survived 2 winters in Auburn, Alabama, where air temperatures were as low as 23 °F (-5 °C) one year and 7 °F (-14 °C) the other. The soil froze to a depth of 1 to 2 inches (2-4 cm) in the colder year [109].

Torpedo grass growth generally improves as temperatures increase. In incubator experiments, buds on torpedo grass rhizomes did not sprout at temperatures <40 °F (5 °C). Sprouting increased from 50% to 96% when temperature increased from 50 °F (10 °C) to 68 °F (20 °C), and was consistently high (92-96%) at temperatures of 68 °F to 95 °F (20-35 °C) [50]. In greenhouse experiments, torpedo grass dry weight, leaf area, and height significantly increased as temperature increased, with greater growth at day/night temperature regimes of 86/77 °F (30/25 °C) than at 81/72 °F (27/22 °C) or 75/64 °F (24/18 °C) (P<0.05) [108]. In greenhouse experiments, shoot elongation and shoot growth increased as temperature increased [50].

Torpedo grass is sensitive to extremely high temperatures. In growth chamber experiments, most potted rhizomes immersed in heated water for 1 hour at temperatures of 120 °F (50 °C) and 130 °F (55 °C) survived, but all rhizomes immersed in heated water for 1 hour at temperatures >140 °F (60 °C) died [109]. In incubator experiments, buds on torpedo grass rhizomes did not sprout at temperatures >113 °F (45 °C) [50].

Soils: Managers from Florida report that torpedo grass grows in many soil types, from sandy, well-drained soils to heavy, waterlogged soils. They suggest that it grows best in soils that are poorly drained and have some degree of water-logging [7]. A nonnative plant guide suggests that it is found most frequently in sandy soils along seacoasts or in poorly drained, heavy soils [49].

Herbarium records and studies document torpedo grass occurring in sandy soils in Florida [14,25,55,113] and Texas [36]. Herbarium records from Texas documented torpedo grass establishment in sand, silt, loam, and clay [36]. Experimental pond studies in Florida showed that sediment type (muck versus sand) did not significantly affect the ability of torpedo grass stem and rhizome fragments to initiate root production and did not affect biomass production [93].

Torpedo grass prefers wet areas [37,92] and established on poorly drained soils in both Florida [25,55,78] and Texas [36]. It frequently establishes in areas experiencing seasonal or prolonged flooding (See Successional Status for more information on this topic). Torpedo grass may also establish in dry areas [44,74]; large rhizomes allow plants to withstand drought [7,49,105].

It is not clear if torpedo grass is limited by soil pH. In greenhouse experiments, torpedo grass plants showed no differences in dry matter production, plant height, or leaf area when grown in soils of pH 4.7 vs. pH 6.7 [107]. Torpedo grass occurred in a coastal marsh near New Orleans, Louisiana, where pH ranged from 5.5 to 8 [17] and on a golf course in southern Florida where pH ranged from 6.6 to 7.7 [14]. It established on "acid" marine deposits in west-central Florida [24].

Torpedo grass is salt tolerant [105], though saline conditions may limit growth. It occurred in a coastal marsh near New Orleans, Louisiana where water salinity averaged 1.73 ±1.22 parts per thousand [17]. In marshes on the Mississippi River delta, torpedo grass cover was reduced both 2 weeks and 1 year after an August hurricane exposed the area to high winds, tidal surges, and increased salinity [18]. In Asia, watering torpedo grass weekly with salty water did not affect normal growth [82].

Elevation: In North America, torpedo grass generally occurs in coastal or lowland areas close to sea level. However, it may occur at higher elevations in mountainous tropical areas in other parts of its range [49,92,104].

SUCCESSIONAL STATUS:
Torpedo grass often establishes in disturbed areas [38,43,104,113,114,115] or early-successional plant communities [28,68], but it is not limited to these areas. At the Archbold Biological Station, Florida, torpedo grass established primarily along fire lanes, in disturbed areas, and along ditches, but it also established in undisturbed hydric and mesic native plant communities, including wet prairies and seasonal ponds, especially where such plant communities were bordered by firelanes [56]. Torpedo grass was frequent on new beaches at the Gulf Islands National Seashore, Florida [68]. In coastal areas of South Carolina, torpedo grass established in newly-created sand dune restoration areas [28].

An invasive plant guide suggests that torpedo grass grows best in open sunny areas but can withstand partial shade [49]. It is commonly documented in open areas (e.g., [14,36,73,113]) and many plant communities lacking a tree canopy, though it has also been documented in some forested areas (see Habitat Types and Plant Communities). In field experiments in Alabama, 75% shading significantly reduced dry matter production, leaf area, and height of torpedo grass (P<0.05) [109]. In greenhouse experiments, increasing photoperiod increased shoot dry weight [92].

Torpedo grass is generally tolerant of flooding. A nonnative species guide suggests that torpedo grass does not tolerate permanently flooded conditions but can withstand occasional flooding [49]. Several sources document it occurring in standing water [29,36,45,93,113]. In the Lake Okeechobee region, torpedo grass established on sites that were inundated for extended periods and tolerated prolonged exposure to relatively deep flooding; the population expanded in areas where the flooding depth was <3.3 feet (1.0 m) for 48 months and >3.3 feet (1.0 m) for 10 months [45]. Along the shores of Lake Okeechobee, torpedo grass grew in water up to 23.0 inches (58.4 cm) deep during high water times in January, when torpedo grass stems extended only 2.5 inches (6.4 cm) above the water's surface [29].

Torpedo grass can reproduce under flooded conditions, but deep water may inhibit rhizome spread and plant growth. In growth trials in Florida, torpedo grass rhizomes with 3 to 4 buds grew and produced flowers after 16 weeks of flooded conditions [96]. Experimental pond studies showed that stem and rhizome fragments remained buoyant through 10 weeks of observations and produced roots when inundated up to depths of 50 inches (125 cm). Only those fragments in water <10 inches (25 cm deep) initiated the production of rhizomes, however. The radial spread of the rhizomes from the parent plant decreased significantly with water depth, as did the number of rhizomes produced (P<0.05). The growth of 15-week-old plants originating from stem fragments was limited as water depth increased [93].

Flooding may have facilitated the establishment of torpedo grass in at least one instance. In southeastern peninsular Florida, historical flooding regimes were restored to wetland areas. Torpedo grass was not present prior to restoration treatments, but was detected after flooding. In one area, "stoloniferous growth on the water surface" led to an increase in frequency from 0% to 86% in 9 years. Its establishment was limited in areas where maidencane was already established [32].

Some types of disturbance may limit torpedo grass. In marshes on the Mississippi River delta, an August hurricane exposed the area to high winds, tidal surges, and increased salinity. Torpedo grass cover was reduced from 6.3% 1 year before the hurricane to 2.4% 2 weeks after the hurricane and 0.5% 1 year after the hurricane [18].

FIRE EFFECTS AND MANAGEMENT

• FIRE EFFECTS
• FUELS AND FIRE REGIMES
• FIRE MANAGEMENT CONSIDERATIONS

Immediate fire effect on plant: Managers report that torpedo grass is often top-killed by fire, but belowground rhizomes usually survive ([7], personal communication [6]). Rhizome mortality may occur when heat from fire penetrates deep into the soil, soil conditions are unusually dry [7], or soils are shallow [98]. As of this writing (2011), it is not known whether torpedo grass seeds survive fire.

Lake Okeechobee wildfire. Photo by Chuck Hanlon, South Florida Water Management District

Postfire regeneration strategy [95]:
Surface rhizome and/or a chamaephytic root crown in organic soil or on soil surface
Rhizomatous herb, rhizome in soil
Geophyte, growing points deep in soil

Fire adaptations and plant response to fire:

Fire adaptations: Torpedo grass exhibits some characteristics that enable it to survive fire. It is rhizomatous (see Vegetative regeneration), and managers report that rhizomes below the soil surface generally survive fire ([7], personal communication [6]). Torpedo grass also often establishes in moist to wet areas where rhizomes are generally protected from fire damage, though aerial portions may burn [7]. Torpedo grass has been observed sprouting following fire [45,46,92,98] (see Plant response to fire, below), herbicide application [14,39,54,59,83,92], grazing [79], cutting, [19,39], and plowing or disking [83,92]. However, rhizomes show some sensitivity to heat, so high-severity fire may kill rhizomes [7]. Growth chamber experiments showed that rhizomes died after 1 hour of immersion in heated water (>140 °F (60 °C)) [109].

As of this writing (2011), the limited available information suggests that torpedo grass is not particularly adapted to establishing in burned areas via dispersed seeds or from the soil seed bank (see Seed production, Seed banking, and Germination).

Plant response to fire: The available information suggests that torpedo grass biomass is reduced following fire but plants often survive and sprout quickly. Mortality may occur in areas where local conditions (e.g., moisture, soil depth) expose rhizomes to heat. Postfire recovery is likely, though recovery may be limited in areas that experience flooding or are treated with herbicides.

Several sources report torpedo grass surviving and sprouting soon after fire in Florida. One manager in Florida observed that torpedo grass exhibits faster postfire recovery than native plants, allowing it to dominate burned areas at the expense of native vegetation (personal communication [6]). Managers report that in areas around Lake Okeechobee where water depth was approximately 2 to 3 inches (5-8 cm), torpedo grass recovered "rapidly and vigorously" following initial biomass reduction after fire, with new growth sprouting from previously dormant buds [7]. After a May prescribed fire near East Lake Tohopekaliga, Florida, torpedo grass sprouted "immediately" in areas that were burned or burned and disked. Rhizome biomass was reduced by 66% in burned areas and 93% in burned and disked areas 100 days after treatment but recovered to approximately 20% of pretreatment levels after 250 days in both treatments [92]. Two studies provide information on aboveground growth after wildfire in the Lake Okeechobee region. One month after an August wildfire, the average torpedo grass height in burned areas was 4 to 8 inches (10-20 cm) compared to ≥30 inches (70 cm) in unburned areas [45]. Six weeks after top-kill from a February wildfire, torpedo grass height averaged 8 inches (20 cm) [46].

In Florida, managers observed torpedo grass mortality in areas exposed to unusual drought conditions, where water levels receded 2 to 3 feet (0.6-0.9 m) below the surface of the ground. Fire consumed both aboveground vegetation and the upper, dry, compacted peat layers to a depth of 3 to 4 inches (8-10 cm). Torpedo grass mortality was also observed following a prescribed fire in 1990 and a wildfire in 1997; in both years, water levels were below the ground's surface [7]. However, dry conditions do not always result in torpedo grass mortality. In 2007, torpedo grass populations in marshes around Lake Okeechobee survived repeated fires during a record low-water period (personal communication [6]).

Flooding after fire may also lead to torpedo grass mortality. One manager from Florida reported that he expected torpedo grass populations to respond well and potentially expand following fire, depending on postfire water levels; he observed torpedo grass mortality and a subsequent population decline in an area that experienced flooding for months following fire (personal communication [6]). In the Florida Everglades, torpedo grass cover was significantly lower 1 year after a mixed-severity prescribed fire in areas flooded after treatment (P<0.001) [98]. See Fire Management Considerations for more information on this study.

Herbicide treatment following fire may reduce torpedo grass populations. See Fire Management Considerations for more information.

Long-term impacts of fire on torpedo grass have not been reported as of this writing (2011).

FUELS AND FIRE REGIMES:

• Fuels
• Fire regimes

Fuels: The limited information available (2011) suggests that torpedo grass populations develop heavy fuel loads that may alter fire characteristics.

In Florida, torpedo grass grows in dense stands and may comprise 80% of the biomass of an area where it establishes (personal communication [6]). Along the shores of Lake Kariba, Zimbabwe, the average standing crop biomass of torpedo grass was 7,620 ± 21.8 kg/ha with an average moisture content of 72.91% ± 0.24 (sampled February to May) [16]. Dead leaves and culms of torpedo grass accumulate in areas without grazing [79].

One manager from Florida believes that populations of torpedo grass accumulate much more fuel than the native plant communities that it replaces, particularly in sawgrass (Cladium jamaicense) and spikerush prairies and American white waterlily sloughs. The increased biomass may lead to "hotter" fires resulting in higher mortality of native species, particularly sawgrass (personal communication [6]).

Fire regimes: It is not clear what fire regime torpedo grass is best adapted to. Observations from Florida suggest that fire severity may impact torpedo grass survival, with high-severity fires potentially killing torpedo grass rhizomes [7]. Repeated fires have resulted in torpedo grass mortality in some situations, but torpedo grass has survived repeated fires under other conditions (see Plant response to fire). Alteration of local fuel characteristics following torpedo grass invasion may change fire regimes.

In North America, torpedo grass invasion is limited to relatively few plant communities, many of which lack fire regime information. See the Fire Regime Table for available information on fire regimes of vegetation communities in which torpedo grass may occur. Find further fire regime information for the plant communities in which this species may occur by entering the species name in the FEIS home page under "Find Fire Regimes".

FIRE MANAGEMENT CONSIDERATIONS:
Potential for postfire establishment and pread: Available information suggests that torpedo grass populations likely survive fire and could potentially spread from existing populations into burned areas. There is little information available to suggest that torpedo grass would establish from seed on burned areas in North America (see Fire adaptations and Plant response to fire).

Preventing postfire establishment and spread: Preventing invasive plants from establishing in weed-free burned areas is the most effective and least costly management method. This may be accomplished through early detection and eradication, careful monitoring and follow-up, and limiting dispersal of invasive plant propagules into burned areas. General recommendations for preventing postfire establishment and spread of invasive plants include:

• Incorporate cost of weed prevention and management into fire rehabilitation plans
• Acquire restoration funding
• Include weed prevention education in fire training
• Minimize soil disturbance and vegetation removal during fire suppression and rehabilitation activities
• Minimize the use of retardants that may alter soil nutrient availability, such as those containing nitrogen and phosphorus
• Avoid areas dominated by high priority invasive plants when locating firelines, monitoring camps, staging areas, and helibases
• Clean equipment and vehicles prior to entering burned areas
• Regulate or prevent human and livestock entry into burned areas until desirable site vegetation has recovered sufficiently to resist invasion by undesirable vegetation
• Monitor burned areas and areas of significant disturbance or traffic from management activity
• Detect weeds early and eradicate before vegetative spread and/or seed dispersal
• Eradicate small patches and contain or control large infestations within or adjacent to the burned area
• Reestablish vegetation on bare ground as soon as possible
• Avoid use of fertilizers in postfire rehabilitation and restoration
• Use only certified weed-free seed mixes when revegetation is necessary

For more detailed information on these topics, see the following publications: [3,8,41,101].

Use of prescribed fire as a control agent: While managers suggest that fire alone is not conducive to torpedo grass control ([7], personal communication [6]), prescribed fire has been successfully used to increase the effectiveness of herbicide treatments ([45,46], personal communications [6,94]). Managers report that torpedo grass plants regenerating after fire are often more susceptible to herbicides than unburned plants. Increased susceptibility may result both from better herbicide contact, as new growth is more exposed after burning has consumed mature torpedo grass thatch, and from greater herbicide penetration through the immature cuticle of young shoots [7]. The results of 2 studies suggest that reestablishement of native vegetation is possible after a reduction in torpedo grass cover due to fire and herbicide treatments [46,98].

The following text details the results of 4 studies integrating prescribed fire and herbicide application.

Study 1 [98]: In the Florida Everglades, areas treated with prescribed fire, herbicides, and combinations of these treatments exhibited significant declines in torpedo grass cover for at least 1 year after treatment. Herbicide-only and herbicide-fire treatments reduced torpedo grass cover more than fire-only treatments. Preferred vegetation established in areas with herbicide-only or herbicide-fire treatments. Flooding after treatment may have contributed to treatment success.

Treatments were applied to constructed stormwater treatment areas where dense torpedo grass cover was limiting the establishment of preferred submerged aquatic vegetation. Prior to treatment, torpedo grass made up the bulk of overall plant cover throughout the study area. The treatments included: 1) prescribed fire followed by imazapyr application; 2) prescribed fire followed by imazapyr and glyphosate application; 3) imazapyr and glyphosate application followed by prescribed fire; 4) prescribed fire only; 5) imazapyr and glyphosate only; and 6) untreated control. Treatment plots were 7 acres (3 ha) in size and treatments were replicated 2 to 5 times. The untreated control was not replicated. Pretreatment vegetation was sampled between December 2003 and February 2004. Treatments were applied in April and May 2004. Posttreatment vegetation was sampled approximately 5 months (September-October 2004) and 11 months (March-April 2005) after treatment. Reported fire information was limited; "burn coverage" varied from 5% to 55% in areas burned in April and 35% to 99% in areas burned in May. The study area was dry during pretreatment data collection and while treatments were applied. It was temporarily flooded prior to treatment in January and February 2004 and continuously flooded after 13 June 2004 following treatments. Mean water depth during posttreatment data collection was 26 inches (65 cm).

Torpedo grass cover declined significantly following treatments (P<0.001). Herbicide-only and herbicide-fire treatments reduced torpedo grass cover more than fire-only treatment.

Burning before or after herbicide application did not seem to improve the efficacy of herbicide treatments. However, the author suggested that fire could still be a useful management tool, particularly in shallow muck soils. Flooding did not impact plant cover (demonstrated by control plots). After treatments and reduction of torpedo grass cover to <1%, preferred submerged aquatic vegetation colonized treated areas. In untreated control areas and areas burned but not treated with herbicides, preferred submerged aquatic vegetation did not establish [98].

Study 2 [46]: In the Lake Okeechobee region burning prior to herbicide treatment resulted in better torpedo grass control than burning after herbicide treatment. Results after 2 years of monitoring suggested that only high herbicide concentrations controlled torpedo grass. Native plant species increased in treated areas.

In February 1997, a wildfire burned approximately 6,000 acres (2,500 ha) of the littoral zone north of Indian Prairie Canal near Lake Okeechobee. Prior to the fire, the area was covered with a dense monoculture of torpedo grass that averaged 3 feet (1 m) in height. About 6 weeks after the fire (April 1997), torpedo grass had regrown to an average height of 8 inches (20 cm) in the burned area. At this time, burned plots were treated with 4 different concentrations of imazapyr. Unburned control plots were also treated with the same imazapyr concentrations. Approximately 3 weeks after herbicide treatments, a wildfire burned the control plots. Thus the study, while originally designed to compare effectiveness of herbicide treatment after fire, ultimately compared effectiveness of postfire herbicide treatment with prefire herbicide treatment. Additional herbicides treatments were not made after the second fire. Treatment efficacy was visually evaluated as percent control of torpedo grass. Control ratings were based on the estimated amount of dead plant material observed above and below the water line and on the amount of regrowth that followed each treatment.

Plots that burned prior to herbicide treatments had consistently less torpedo grass than those burned after herbicide treatments at all imazapyr concentrations. By 118 weeks after treatment, torpedo grass was considered controlled only in those plots burned before herbicide treatment and treated with the 2 highest concentrations of imazapyr [46].

Torpedo grass stem counts were conducted, but due to logistical constraints, stem counts were only done in areas burned prior to herbicide treatment, not those burned after herbicide treatments. There were large reductions in stem density in the burned plots that were subsequently treated with the 2 highest rates of imazapyr.

In areas where high concentrations of herbicides were applied, native plant species (e.g., bulltongue arrowhead and pickerelweed), became the dominant vegetation in less than 1 year [46].

Study 3 [45]: Managers in the Lake Okeechobee region integrated fire and herbicide treatments in attempts to control torpedo grass at the landscape level. In August 2000, nearly 5,000 acres (2,000 ha) of marsh vegetation were ignited using a drip torch suspended from a helicopter. Imazapyr was applied in September 2000 to burned and unburned sites. At the time of herbicide treatments, average torpedo grass height was 4 to 8 inches (10-20 cm) in the burned area and commonly >30 inches (70 cm) in the unburned area. Aerial color infrared imagery was used to measure torpedo grass cover on the landscape before and after treatments. Eight months after herbicide treatments, torpedo grass control was 95% and 60% in 2 burned plots and 40% in an unburned plot, suggesting that fire increased the efficacy of herbicide treatments, at least in the short term. The authors suggested that regional differences (e.g., soil moisture) may have impacted results, but noted that treatments tended to be most effective in areas burned prior to herbicide treatment. They suggested that fire reduced torpedo grass biomass, increasing the exposure of sediment and newly emerged vegetation to herbicides. The authors mentioned several other treatments combining fire and herbicides, all of which seemed to control torpedo grass at a rate greater than its rate of spread in the area [45].

Study 4 [92]: One study in Florida examined the combination of fire, mechanical treatments, and herbicide application to control torpedo grass. While control was generally high 1 year after integrated treatments, the results suggested that burning, mowing, and disking did not enhance the effectiveness of herbicide in torpedo grass control, and the author suggested that these techniques would not result in long-term suppression of torpedo grass.

Integrated treatments were applied to control a torpedo grass monoculture established in the littoral zone of East Lake Tohopekaliga, Florida. Lake levels were drawn down in 1990 and 1991 to facilitate treatments. In May 1990, a 57-acre (23-ha) field of torpedo grass was burned. Though fire information was not reported, the fire did consume all torpedo grass foliage and thatch. After the fire, 50% of the area was disked to a depth of 8 inches (20 cm). Glyphosate was applied at several concentrations 3 times: in early July, late July, and August 1990. In 1991, 2 acres (1 ha) of the previously burned-disked area were mowed and disked to a depth of 8 inches (20 cm). Other areas were mowed without disking. Glyphosate was applied at several concentrations in early July. Burned areas without herbicide application were maintained in both years in areas with all mechanical treatments.

Torpedo grass shoot biomass was entirely consumed by the fire, though sprouting occurred "immediately" in areas that were burned or burned and disked. Shoot biomass recovered to approximately 20% of its pretreatment biomass 750 days after treatment. Rhizome biomass was reduced by 66% in burned areas and 93% in burned and disked areas 100 days after treatment. Rhizome biomass recovered to approximately 20% of its pretreatment biomass after 250 days and then remained constant through 750 days in burned areas with different mechanical treatments.

Herbicide application in addition to fire and mechanical treatments did not result in increased torpedo grass control. Visual observations confirmed that all rates of glyphosate application, regardless of other treatment, provided 100% control of torpedo grass shoots 2 months after herbicide application. One year after treatment, however, all rates of glyphosate application provided approximately the same amount of control of torpedo grass shoots (>78%), with the exception of the lowest concentration of glyphosate in areas that were not disked (55%). Rhizome response was generally less than shoot response for all glyphosate rates in both combinations of mechanical treatment.

MANAGEMENT CONSIDERATIONS

• FEDERAL LEGAL STATUS
• OTHER STATUS
• IMPORTANCE TO WILDLIFE AND LIVESTOCK
• OTHER USES
• IMPACTS AND CONTROL

Palatability and nutritional value: Torpedo grass has been planted throughout the world as forage for domestic livestock [2,44,65,69,79]. A nonnative species guide reports that, though used for pasturage, torpedo grass has relatively low nutritional value, protein content, and palatability compared to other grasses. Its advantage as a forage grass is that it is relatively palatable when young and can withstand heavy grazing and trampling [49]. It can be fed to cattle either green or as hay [31]. However, torpedo grass was reported as poisonous to horses in Florida [92,109].

Torpedo grass may have some value as food for wildlife. Populations of torpedo grass near Lake Okeechobee supported a diverse arthropod and nematode fauna, and plants were not limited by invertebrate herbivory or damage [29]. In feeding trials in Florida, it was consumed by the nonnative channeled apple snail (Pomacea insularum) [4,5]. On the Mississippi River delta, both above- and belowground vegetation of torpedo grass was eaten by snow geese and brants in the fall [72]. It was eaten by redbread tilapia (Tilapia rendalli) in Lake Kariba in Zimbabwe [16]. Seeds of torpedo grass were found in fecal pellets of wild spur-thighed tortoises in Spain [26].

Cover value: No information is available on this topic.

OTHER USES:
Torpedo grass may be used as a soil binder [31,44] or for erosion control [50,105]. It has been evaluated for use in improving water quality; in laboratory experiments, torpedo grass was credited with adjusting pH and reducing toxic chemicals and dissolved minerals in water supplies [111]. In Taiwan, torpedo grass was evaluated for use as a substrate for oyster mushroom (Pleurotus citrinopileatus) cultivation [66]. In Indonesia, torpedo grass rhizomes are used to treat abnormal menstruation [31].

IMPACTS AND CONTROL:

Impacts: Torpedo grass invasion is problematic in agricultural systems, including tea, sugarcane, coconut, cacao, cotton, rubber, rice, and citrus plantations [92]. It is also problematic in pastures and along canal banks and roadsides [109]. Torpedo grass invasion in and around water bodies may interfere with flood control, navigation, recreation, and irrigation [29].

In the United States, the impacts of torpedo grass invasion have been most documented in Florida. An invasive plant management guide for Florida reports that torpedo grass was established in > 70% of Florida’s public waters by 1992 [69]. As of 2002, torpedo grass had displaced more than 16,000 acres (6,500 ha) of the 100,000 acres (40,000 ha) of native plant communities in Lake Okeechobee’s marsh [7]. In the late 1990s, torpedo grass management in flood control systems cost approximately $2 million a year [65].

Photo by Ann Murray, University of Florida, Bugwood.org

Invasive plant management guides suggest that invasive torpedo grass populations displace native vegetation [69,105]. Over a 5-year period in the Lake Okeechobee region, 20 acres (8 ha) of spikerush and open water were replaced by torpedo grass. Torpedo grass cover increased by 32%, from 62 acres (25 ha) in 1994 to 82 acres (33 ha) in 1999 [45]. In the Florida Everglades, herbicide and prescribed fire treatments were applied to constructed stormwater treatment areas where dense torpedo grass cover was limiting the establishment of preferred submerged aquatic vegetation [98]. In coastal areas of South Carolina, torpedo grass established in sand dune restoration areas and was expected to replace the desired planted species [28].

Torpedo grass may affect ecosystem processes in water channels by stabilizing lake and stream edges [42]. In the Everglades drainage basin, persistent high cover of nonnative macrophytes, including torpedo grass, resulted in a high accumulation of organic materials that depressed dissolved oxygen concentrations. In Lake Istokpoga, Florida, hypoxic conditions occurred in areas densely vegetated by torpedo grass and other nonnative macrophytes [12]. Areas with dense stands of torpedo grass are considered poor habitat for fish because high stem densities inhibit fish movement, and dissolved oxygen concentrations are too low [46].

Control: Torpedo grass is difficult to control. Plants possess numerous dormant buds associated with extensive rhizomes [64] and can sprout from deep in the soil [109]. Plants allocate a high proportion of resources to belowground biomass [96]. Plants sprout following rhizome fragmentation [109] or destruction of aboveground vegetation [39]. Several years of treatment may be needed to control torpedo grass [64].

In all cases where invasive species are targeted for control, no matter what method is employed, the potential for other invasive species to fill their void must be considered [9]. Control of biotic invasions is most effective when it employs a long-term, ecosystem-wide strategy rather than a tactical approach focused on battling individual invaders [70].

Prevention: An invasive plant management guide from Florida suggests that maintaining healthy ecosystems with good species diversity and limiting the presence of open and disturbed areas may help to deter establishment of nonnative species like torpedo grass. Population spread may also be limited by preventing the fragmentation and spread of torpedo grass rhizomes, controlling established populations near waterways [69], not accepting contaminated materials such as fill dirt and hay, and cleaning vegetation off of boat trailers and machinery [92].

It is commonly argued that the most cost-efficient and effective method of managing invasive species is to prevent their establishment and spread by maintaining "healthy" natural communities [70,91] (e.g., avoid road building in wildlands [100]) and by monitoring several times each year [57]. Managing to maintain the integrity of the native plant community and mitigate the factors enhancing ecosystem invasibility is likely to be more effective than managing solely to control the invader [48].

Weed prevention and control can be incorporated into many types of management plans, including those for logging and site preparation, grazing allotments, recreation management, research projects, road building and maintenance, and fire management [101]. See the Guide to noxious weed prevention practices [101] for specific guidelines in preventing the spread of weed seeds and propagules under different management conditions.

Fire: For information on the use of prescribed fire to control this species, see Fire Management Considerations.

Cultural control: The presence of other vegetation may limit the establishment or spread of torpedo grass. In a wetland in southeastern peninsular Florida, torpedo grass establishment and spread was limited or nonexistent in areas where maidencane, a native species, was already established [32].

Physical or mechanical control: An invasive plant management guide from Florida suggests that mechanical methods are only moderately effective for torpedo grass control [69]. Mechanical control methods often produce numerous rhizome fragments capable of producing aerial shoots even if buried relatively deeply in the soil [107,109].

Tillage has the potential to fragment rhizomes and stimulate sprouting [65,69]. In field experiments, torpedo grass sprouted following tilling, with most sprouts emerging 50 to 90 days after tilling. Because associated greenhouse experiments found that rhizomes with fewer nodes were less likely to sprout and that sprouting decreased with depth of burial, the authors suggested that fragmenting rhizomes by cross-plowing and deeply burying rhizomes by plowing below 12 inches (30 cm) might reduce sprouting after treatment [53]. In sugarcane fields in Taiwan, hand-hoeing torpedo grass depleted rhizome reserves, but had to be repeated 6 times to achieve control [83]. An invasive plant management guide suggests that continuous tillage could provide control but is impractical in natural areas [69].

Digging may be an effective means of controlling small patches of torpedo grass, but it is difficult to remove all rhizomes [105]. Digging is often unsuccessful because it is time consuming, expensive, and may result in the scattering of rhizome fragments [20].

Mowing is only marginally effective [69]. In Taiwan, repeated mowing through a growing season limited the development of new rhizomes, but did not ultimately prevent regeneration [82]. Torpedo grass withstands grazing and trampling [49,79].

The results of experimental pond studies in Florida suggested that flooding or maintaining deep water could limit torpedo grass establishment and growth. However, the authors caution that frequent flooding could negatively impact other wetland plants in Florida plant communities [93].

Biological control: As of this writing (2011), no biological agent has been identified to control torpedo grass. Laboratory experiments suggest that fungal pathogens may be useful in controlling torpedo grass [90]. In Florida, populations of torpedo grass supported a diverse arthropod and nematode fauna, but the plant was not limited by invertebrate herbivory or damage [29]. In feeding trials in Florida, the nonnative channeled apple snail fed heavily on torpedo grass but also consumed native species, suggesting that it would not be an appropriate biocontrol for torpedo grass or other species nonnative to Florida [5].

Biological control of invasive species has a long history that indicates many factors must be considered before using biological controls. Refer to these sources: [103,110] and the Weed control methods handbook [99] for background information and important considerations for developing and implementing biological control programs.

Chemical control: Herbicide application is the most widely-used method for controlling torpedo grass, though plants may sprout from rhizomes [14,19,39,54,59,83,89] or tillering may increase [19] following treatment. Repeated applications may be needed to achieve control [14,19,54,69], but may not always work [83,89]. In greenhouse growth trials, the level of torpedo grass control by herbicides varied by strength of application, length of exposure, and number of treatments [19]. Greenhouse studies suggested that young torpedo grass plants or plants in the reproductive stage may be most susceptible to herbicides [92]. Integration with other methods may increase the effectiveness of herbicide treatments (See Use of prescribed fire as a control agent).

In Florida, the use of herbicides to control torpedo grass is complicated by concerns about impacts on nontarget vegetation and the use of herbicides in aquatic systems [45,69]. Chemical control may also be expensive, [59], labor intensive, and impractical on a large scale [39].

Herbicides are effective in gaining initial control of a new invasion or a severe infestation, but they are rarely a complete or long-term solution to weed management [15]. See the Weed control methods handbook [99] for considerations on the use of herbicides in natural areas and detailed information on specific chemicals. See the following references for specific recommendations on chemical control of torpedo grass: [14,19,39,46,54,59,60,64,69,82,83,89,92].

APPENDIX: FIRE REGIME TABLE

Panicum repens: REFERENCES

1. Akamine, Hikaru; Hossain, Mohammad Amzad; Ishimine, Yukio; Kuramochie, Hitoshi. 2007. Bud sprouting of torpedograss (Panicum repens L.) as influenced by the rhizome moisture content. Weed Biology and Management. 7(3): 188-191. [81098]

2. Ali, S. I.; Qaiser, M.; [and others]. 2011. Flora of Pakistan, [Online]. Islamabad: Pakistan Agricultural Research Council; Karachi, Pakistan: University of Karachi; St. Louis, MO: Missouri Botanical Garden. In: eFloras. St. Louis, MO: Missouri Botanical Garden; Cambridge, MA: Harvard University Herbaria (Producers). Available: http://www.efloras.org/flora_page.aspx?flora_id=5; http://www.mobot.org/MOBOT/research/pakistan/welcome.shtml [73152]

3. Asher, Jerry; Dewey, Steven; Olivarez, Jim; Johnson, Curt. 1998. Minimizing weed spread following wildland fires. In: Christianson, Kathy, ed. Western Society of Weed Science: Proceedings; 1998 March 10-12; Waikoloa, HI. In: Proceedings, Western Society of Weed Science. 51: 49. Abstract. [40409]

4. Baker, Patrick; Zimmanck, Frank; Baker, Shirley M. 2010. Feeding rates of an introduced freshwater gastropod Pomacea insularum on native and nonindigenous aquatic plants in Florida. Journal of Molluscan Studies. 76(2): 138-143. [81099]

5. Baker, Shirley M.; Zimmanck, Frank; Baker, Patrick. 2008. From alligator weed to wapato: will invasive channeled apple snails eat us out of house and home? Journal of Shellfish Research. 27(4): 988. Abstract. [81144]

6. Bodle, Mike. 2010. [Email to Katherine Stone]. December 10. Regarding fire and torpedograss. West Palm Beach, FL: South Florida Water Management District. On file with: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory, Missoula, MT; FEIS files. [82005]

7. Bodle, Mike; Hanlon, Chuck. 2001. Damn the torpedo grass! Wildland Weeds. 4: 6-12. [81284]

8. Brooks, Matthew L. 2008. Effects of fire suppression and postfire management activities on plant invasions. In: Zouhar, Kristin; Smith, Jane Kapler; Sutherland, Steve; Brooks, Matthew L., eds. Wildland fire in ecosystems: Fire and nonnative invasive plants. Gen. Tech. Rep. RMRS-GTR-42-vol. 6. Ogden, UT: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station: 269-280. [70909]

9. Brooks, Matthew L.; Pyke, David A. 2001. Invasive plants and fire in the deserts of North America. In: Galley, Krista E. M.; Wilson, Tyrone P., eds. Proceedings of the invasive species workshop: The role of fire in the control and spread of invasive species; Fire conference 2000: 1st national congress on fire ecology, prevention, and management; 2000 November 27 - December 1; San Diego, CA. Misc. Publ. No. 11. Tallahassee, FL: Tall Timbers Research Station: 1-14. [40491]

10. Brown, Clair A. 1930. Plants observed on an excursion to Grand Isle, Louisiana. Bulletin of the Torrey Botanical Club. 57(7): 509-513. [81100]

11. Buller, Roderic E.; Hernanez X., E.; Gonzalez, Martin H. 1960. Grassland and livestock regions of Mexico. Journal of Range Management. 13(1): 1-6. [81101]

12. Bunch, Aaron J.; Allen, Micheal S.; Gwinn, Daniel C. 2010. Spatial and temporal hypoxia dynamics in dense emergent macrophytes in a Florida lake. Wetlands. 30(3): 429-435. [81102]

13. Burney, James L., Jr.; Buhler, Jean M. 1991. Wastewater treatment and habitat availability in a created freshwater wetland. Restoration and Management Notes. 9(1): 43-44. [15701]

14. Busey, Philip. 2003. Reduction of torpedograss (Panicum repens) canopy and rhizomes by quinclorac split applications. Weed Technology. 17(1): 190-194. [81146]

15. Bussan, Alvin J.; Dyer, William E. 1999. Herbicides and rangeland. In: Sheley, Roger L.; Petroff, Janet K., eds. Biology and management of noxious rangeland weeds. Corvallis, OR: Oregon State University Press: 116-132. [35716]

16. Caulton, M. S. 1977. A quantitative assessment of the daily ingestion of Panicum repens L. by Tilapia rendalli boulenger (Cichlidae) in Lake Kariba. Transactions of the Rhodesia Scientific Association. 58(6): 38-42. [81147]

17. Chabreck, Robert H. 1972. Vegetation, water and soil characteristics of the Louisiana coastal region. Bulletin 664. Baton Rouge, LA: Louisiana State University, Louisiana Agricultural Experiment Station. 72 p. [19976]

18. Chabreck, Robert H.; Palmisano, A. W. 1973. The effects of Hurricane Camille on the marshes of the Mississippi River Delta. Ecology. 54(5): 1118-1123. [68788]

19. Chandrasena, J. P. N. R. 1990. Torpedograss (Panicum repens L.) control with lower rates of glyphosate. Tropical Pest Management. 36(4): 336-342. [81162]

20. Chandrasena, J. P. N. R.; Dhammika, W. H. Y. 1998. Studies on the biology of Panicum repens L. 1. Comparative morphological development of three selections from different geographic localities in Sri Lanka. Tropical Pest Management. 34(3): 291-297. [81149]

21. Chandrasena, J. P. N. R.; Peiris, H. C. P. 1989. Studies on the biology of Panicum repens L. II. Intraspecific competition and resource allocation. Tropical Pest Management. 35(3): 316-320. [81157]

22. Chou, Chang-Hung. 1994. Allelopathy and sustainable agriculture. In: Inderjit; Dakshini, K. M. M.; Einhellig, Frank A., eds. Allelopathy: Organisms, processes, and applications. American Chemical Society Symposium Series: Volume 582. Washington, DC: American Chemical Society. 211-223. [81172]

23. Chu, L. M. 2008. Natural revegetation of coal fly ash in a highly saline disposal lagoon in Hong Kong. Applied Vegetation Science. 11(3): 297-306. [79752]

24. Clewell, Andre F. 1985. Guide to the vascular plants of the Florida Panhandle. Tallahassee, FL: Florida State University Press. 605 p. [13124]

25. Clewell, Andre F.; Raymond, Christina; Coultas, C. L.; Dennis, W. Michael; Kelly, James P. 2009. Spatially narrow wet prairies. Castanea. 74(2): 146-159. [81173]

26. Cobo, Margarita; Andreu, Ana C. 1988. Seed consumption and dispersal by the spur-thighed tortoise Testudo graeca. Oikos. 51(3): 267-273. [81174]

27. Cole, N. H. Ayodele. 1973. Soil conditions, zonation and species diversity in a seasonally flooded tropical grass-herb swamp in Sierra Leone. Journal of Ecology. 61(3): 831-847. [81175]

28. Conner, William; Socha, Tommy. 2003. Growth and survival of plants used to control erosion on the Atlantic Intracoastal Waterway. Southeastern Biology. 50(2): 110. Abstract. [81222]

29. Cuda, J. P.; Dunford, J. C.; Leavengood, J. M., Jr. 2007. Invertebrate fauna associated with torpedograss, Panicum repens (Cyperales: Poaceae), in Lake Okeechobee, Florida, and prospects for biological control. The Florida Entomologist. 90(1): 238-248. [81177]

30. Cutshall, Jack R. 1994. Gulf Coast fresh marsh: SRM 807. In: Shiflet, Thomas N., ed. Rangeland cover types of the United States. Denver, CO: Society for Range Management: 114-115. [67474]

31. Datta, S. C.; Banerjee, A. K. 1978. Useful weeds of West Bengal rice fields. Economic Botany. 32(3): 297-310. [81203]

32. David, Peter G. 1999. Response of exotics to restored hydroperiod at Dupuis Reserve, Florida. Restoration Ecology. 7(4): 407-410. [81204]

33. Drawe, D. Lynn. 1994. Cordgrass: SRM 726. In: Shiflet, Thomas N., ed. Rangeland cover types of the United States. Denver, CO: Society for Range Management: 101-102. [67377]

34. Dutton, Bryan E.; Thomas, R. Dale. 1991. The vascular flora of Cameron Parish, Louisiana. Castanea. 56(1): 1-37. [73744]

35. Eleuterius, Lionel N.; McDaniel, Sidney. 1978. The salt marsh flora of Mississippi. Castanea. 43(2): 86-95. [81207]

36. Flora of Texas Project. 2010. Flora of Texas database, [Online]. In: Plant Resources Center. Austin, TX: University of Texas at Austin, Plant Resources Center; Flora of Texas Consortium (Producer). Available: http://www.biosci.utexas.edu/prc/Tex.html. [80314]

37. Futch, Stephen H.; Hall, David W. 2004. Identification of grass weeds in Florida citrus. Gainesville, FL: University of Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences. 8 p. [81208]

38. Genelle, Pierre; Fleming, Glenn. 1978. The vascular flora of "The Hammock", Dunedin, Florida. Castanea. 43(1): 29-54. [75444]

39. Gettys, Lyn A.; Sutton, David L. 2004. Comparison of torpedograss and pickerelweed susceptibility to glyphosate. Journal of Aquatic Plant Management. 42: 1-4. [81210]

40. Godfrey, Robert K.; Wooten, Jean W. 1979. Aquatic and wetland plants of southeastern United States: Monocotyledons. Athens, GA: The University of Georgia Press. 712 p. [16906]

41. Goodwin, Kim; Sheley, Roger; Clark, Janet. 2002. Integrated noxious weed management after wildfires. EB-160. Bozeman, MT: Montana State University, Extension Service. 46 p. Available online: http://www.msuextension.org/store/Products/Integrated-Noxious-Weed-Management-After-Wildfires__EB0160.aspx [2011, January 20]. [45303]

42. Gordon, Doria R. 1998. Effects of invasive, non-indigenous plant species on ecosystem processes: lessons from Florida. Ecological Applications. 8(4): 975-989. [53761]

43. Hall, David W. 1978. The grasses of Florida. Gainesville, FL: University of Florida. 498 p. Dissertation. [53560]

44. Hall, David W.; Currey, Wayne L.; Orsenigo, Joseph R. 1998. Weeds from other places: the Florida beachhead is established. Weed Technology. 12(4): 720-725. [79819]

45. Hanlon, Charles G.; Brady, Mark. 2005. Mapping the distribution of torpedograss and evaluating the effectiveness of torpedograss management activities in Lake Okeechobee, Florida. Journal of Aquatic Plant Management. 43: 24-29. [81214]

46. Hanlon, Charles G.; Langeland, Ken. 2000. Comparison of experimental strategies to control torpedograss. Journal of Aquatic Plant Management. 38: 40-47. [81212]

47. Hann, Wendel; Havlina, Doug; Shlisky, Ayn; [and others]. 2010. Interagency fire regime condition class (FRCC) guidebook, [Online]. Version 3.0. In: FRAMES (Fire Research and Management Exchange System). National Interagency Fuels, Fire & Vegetation Technology Transfer (NIFTT) (Producer). Available: http://www.fire.org/niftt/released/FRCC_Guidebook_2010_final.pdf. [81749]

48. Hobbs, Richard J.; Humphries, Stella E. 1995. An integrated approach to the ecology and management of plant invasions. Conservation Biology. 9(4): 761-770. [44463]

49. Holm, LeRoy G.; Plocknett, Donald L.; Pancho, Juan V.; Herberger, James P. 1977. The world's worst weeds: distribution and biology. Honolulu, HI: University Press of Hawaii. 609 p. [20702]

50. Hossain, Mohammad Amzad; Akamine, Hikaru; Nakamura, Ichiro; Ishimine, Yukio; Kuramochi, Hitoshi. 2001. Influence of temperature levels and planting time on the sprouting of rhizome-bud and biomass production of torpedograss (Panicum repens L.) in Okinawa Island, southern Japan. Weed Biology and Management. 1(3): 164-169. [81226]

51. Hossain, Mohammad Amzad; Ishimine, Yukio; Akamine, Hikaru; Kuramochi, Hitoshi. 2004. Effect of nitrogen fertilizer application on growth, biomass production and N-uptake of torpedograss (Panicum repens L.). Weed Biology and Management. 4(2): 86-94. [81228]

52. Hossain, Mohammad Amzad; Ishimine, Yukio; Akamine, Hikaru; Murayama, Seiichi. 1996. Growth and development characteristics of torpedograss (Panicum repens L.) in Okinawa Island, Southern Japan. Weed Research, Japan. 41(4): 323-331. [81283]

53. Hossain, Mohammad Amzad; Ishimine, Yukio; Akamine, Hikaru; Murayama, Seiichi; Uddin, S. M. Moslem; Kuniyoshi, Kiyoshi. 1999. Effect of burial depth on emergence of Panicum repens. Weed Science. 47(6): 651-656. [81223]

54. Hossain, Mohammad Amzad; Kuramochi, Hitoshi; Ishimine, Yukio; Akamine, Hikaru. 2001. Application timing of asulam for torpedograss (Panicum repens L.) control in sugarcane in Okinawa Island. Weed Biology and Management. 1(2): 108-114. [81224]

55. Huffman, Jean M.; Judd, Walter S. 1998. Vascular flora of Myakka River State Park, Sarasota and Manatee Counties, Florida. Castanea. 63(1): 25-50. [79821]

56. Hutchinson, Jeffrey T.; Menges, Eric S. 2006. Evaluation of the invasiveness of non-native plants at the Archbold Biological Station. Florida Scientist. 69: 62-68. [80869]

57. Johnson, Douglas E. 1999. Surveying, mapping, and monitoring noxious weeds on rangelands. In: Sheley, Roger L.; Petroff, Janet K., eds. Biology and management of noxious rangeland weeds. Corvallis, OR: Oregon State University Press: 19-36. [35707]

58. Kartesz, John T. 1999. A synonymized checklist and atlas with biological attributes for the vascular flora of the United States, Canada, and Greenland. 1st ed. In: Kartesz, John T.; Meacham, Christopher A. Synthesis of the North American flora (Windows Version 1.0), [CD-ROM]. Chapel Hill, NC: North Carolina Botanical Garden (Producer). In cooperation with: The Nature Conservancy; U.S. Department of Agriculture, Natural Resources Conservation Service; U.S. Department of the Interior, Fish and Wildlife Service. [36715]

59. Ketterer, Eileen Ann. 2007. Evaluation of growth regulating herbicides for improved management of cogongrass and torpedograss. Gainesville, FL: University of Florida. 97 p. Thesis. [81231]

60. Kline, W. N.; Duquesnel, J. G. 1996. Management of invasive exotic plants with herbicides in Florida. Down to Earth. 51(2): 22-28. [75556]

61. Kuchler, A. W. 1964. Southern cordgrass prairie (Spartina alterniflora). In: Kuchler, A. W. Manual to accompany the map of potential vegetation of the conterminous United States. Special Publication No. 36. New York: American Geographical Society: 79. [67762]

62. LANDFIRE Rapid Assessment. 2005. Reference condition modeling manual (Version 2.1), [Online]. In: LANDFIRE. Cooperative Agreement 04-CA-11132543-189. Boulder, CO: The Nature Conservancy; U.S. Department of Agriculture, Forest Service; U.S. Department of the Interior (Producers). 72 p. Available: https://www.landfire.gov /downloadfile.php?file=RA_Modeling_Manual_v2_1.pdf [2007, May 24]. [66741]

63. LANDFIRE Rapid Assessment. 2007. Rapid assessment reference condition models, [Online]. In: LANDFIRE. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Lab; U.S. Geological Survey; The Nature Conservancy (Producers). Available: https://www.landfire.gov /models_EW.php [2008, April 18] [66533]

64. Langeland, K. A.; Ferrell, J. A.; Sellers, B.; Macdonald, G. E.; Stocker, R. K. 2009. Control of nonnative plants in natural areas of Florida, [Online]. In: Electronic Data Information Source (EDIS) database--Publication #SP 242. Gainesville, FL: University of Florida, Institute of Food and Agricultural Sciences Extension (Producer). Available: http://edis.ifas.ufl.edu/pdffiles/WG/WG20900.pdf [2009, October 20]. [75659]

65. Langeland, Kenneth A.; Burks, K. Craddock, eds. 1998. Identification and biology of non-native plants in Florida's natural areas. UF/IFAS Publication # SP 257. Gainesville, FL: University of Florida. 165 p. Available online: http://www.fleppc.org/ID_book.htm [2010, August 26]. [72429]

66. Liang, Zeng-Chin; Wu, Chiu-Yeh; Shieh, Zheng-Liang; Cheng, Shou-Liang. 2009. Utilization of grass plants for cultivation of Pleurotus citrinopileatus. International Biodeterioration & Biodegradation. 63(4): 509-514. [81246]

67. Lloyd, Francis E.; Tracy, S. M. 1901. The insular flora of Mississippi and Louisiana. Bulletin of the Torrey Botanical Club. 28(2): 61-101. [81247]

68. Looney, Paul B.; Gibson, David J.; Blyth, Amelie; Cousens, Michael I. 1993. Flora of the Gulf Islands National Seashore, Perdido Key, Florida. Bulletin of the Torrey Botanical Club. 120(3): 327-341. [81248]

69. MacDonald, Gregory E.; Ferrell, Jay; Sellers, Brent; Langeland, Ken; Duperron-Bond, Ona Tina; Ketterer-Guest, Eileen. 2008. Torpedograss--Panicum repens, [Online]. In: Plant info and images--Invasive plant management plans. In: Center for Aquatic and Invasive Plants. Gainesville, FL: University of Florida, Institute of Food and Agricultural Sciences, Center for Aquatic and Invasive Plants (Producer). Available: http://plants.ifas.ufl.edu/node/308 [2011, January 24]. [81756]

70. Mack, Richard N.; Simberloff, Daniel; Lonsdale, W. Mark; Evans, Harry; Clout, Michael; Bazzaz, Fakhri A. 2000. Biotic invasions: causes, epidemiology, global consequences, and control. Ecological Applications. 10(3): 689-710. [48324]

71. Martinez, M. L.; Valverde, T.; Moreno-Casasola, P. 1992. Germination response to temperature, salinity, light and depth of sowing of ten tropical dune species. Oecologia. 92(3): 343-353. [81258]

72. McAtee, W. L. 1910. Notes on Chen caerulescens, Chen rossi, and other waterfowl in Louisiana. The Auk. 27: 337-339. [19987]

73. McJunkin, David M. 1977. Aspects of cypress domes in southeastern Florida: a study in micro-phytogeography. Boca Raton, FL: Florida Atlantic University. 175 p. Thesis. [49161]

74. Miller, G. J.; Jones, S. B., Jr. 1967. The vascular flora of Ship Island, Mississippi. Castanea. 32(2): 84-99. [81266]

75. Miller, James H. 2003. Nonnative invasive plants of southern forests: A field guide for identification and control. Gen. Tech. Rep. SRS-62. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station. 93 p. Available online: http://www.srs.fs.usda.gov/pubs/gtr/gtr_srs062/ [2004, December 10]. [50788]

76. Moore, Frank R.; Kerlinger, Paul; Simons, Ted R. 1990. Stopover on a Gulf Coast barrier island by spring trans-Gulf migrants. The Wilson Bulletin. 102(3): 487-500. [81267]

77. Moreno-Casasola, Patricia. 1988. Patterns of plant species distribution on coastal dunes along the Gulf of Mexico. Journal of Biogeography. 15(5/6): 787-806. [81286]

78. Myers, James H.; Wunderlin, Richard P. 2003. Vascular flora of Little Manatee River State Park, Hillsborough County, Florida. Castanea. 68(1): 56-74. [75824]

79. Nemoto, Masayuki; Panchaban, Santibhab. 1991. Influence of livestock grazing on vegetation in a saline area in northeast Thailand. Ecological Research. 6(3): 265-276. [81268]

80. Nolfo-Clements, Lauren E. 2006. Vegetative survey of wetland habitats at Jean Lafitte National Historical Park and Preserve in southeastern Louisiana. Southeastern Naturalist. 5(3): 499-514. [80764]

81. Penfound, William T.; O'Neill, M. E. 1934. The vegetation of Cat Island, Mississippi. Ecology. 15(1): 1-16. [81270]

82. Peng, Sheng Y.; Twu, L. T. 1979. Studies on the regenerative capacity of rhizomes of torpedo grass (Panicum repens Linn.). 1. Characteristics in sprouting of rhizomes and resistance to herbicides and environmental adversities. Journal of the Agricultural Association of China. 107: 61-74. [81326]

83. Peng, Sheng Y.; Twu, Lian T. 1974. Effect of competition by Panicum repens L. on sugarcane, and eradication by herbicides. In: Dick, J.; Collingwood, D. J., eds. Proceedings, 15th congress--International Society of Sugar Cane Technologists; 1974 June 13-29; Durban, South Africa. Volume 2: Agronomy, Plant Physiology, Agricultural Engineering. Durban, South Africa: The Executive Committee of the International Society of Sugar Cane Technologists: 794-808. [81313]

84. Perkins, Carroll J. 1968. Controlled burning in the management of muskrats and waterfowl in Louisiana coastal marshes. In: Proceedings, annual Tall Timbers fire ecology conference; 1968 March 14-15; Tallahassee, FL. No. 8. Tallahassee, FL: Tall Timbers Research Station: 269-280. [16941]

85. Ponzio, Kimberli J.; Miller, Steven J.; Underwood, Elizabeth; Rowe, Sean P.; Voltolina, Douglas J.; Miller, Timothy D. 2006. Responses of a willow (Salix caroliniana Michx.) community to roller-chopping. Natural Areas Journal. 26(1): 53-60. [64546]

86. Raunkiaer, C. 1934. The life forms of plants and statistical plant geography. Oxford: Clarendon Press. 632 p. [2843]

87. Royal Botanic Garden Edinburgh. 2011. Flora Europaea, [Online]. Edinburgh, UK: Royal Botanic Garden Edinburgh (Producer). Available: http://rbg-web2.rbge.org.uk/FE/fe.html. [41088]

88. Rundell, Hannelore; Woods, Michael. 2001. The vascular flora of Ech Lake, Alabama. Castanea. 66(4): 352-362. [75321]

89. Sartain, Rachel Tenpenny. 2003. Physiological factors affecting the management of torpedograss (Panicum repens (L.) Beauv.). Gainesville, FL: University of Florida. 46 p. Thesis. [81287]

90. Shabana, Yasser M.; Stiles, Carol M.; Charudattan, R.; Abou Tabl, Ayman H. 2010. Evaluation of bioherbicidal control of tropical signalgrass, crabgrass, smutgrass, and torpedograss. Weed Technology. 24(2): 165-172. [81273]

91. Sheley, Roger; Manoukian, Mark; Marks, Gerald. 1999. Preventing noxious weed invasion. In: Sheley, Roger L.; Petroff, Janet K., eds. Biology and management of noxious rangeland weeds. Corvallis, OR: Oregon State University Press: 69-72. [35711]

92. Smith, Brian Eugene. 1993. Ecophysiological and technological factors that influence the management of torpedograss [Panicum repens (L.) Beauv.]. Gainesville, FL: University of Florida. 92 p. Thesis. [81236]

93. Smith, Dian H.; Smart, R. Michael; Hanlon, Charles G. 2004. Influence of water level on torpedograss establishment in Lake Okeechobee, Florida. Lake and Reservoir Management. 20(1): 1-13. [81288]

94. Smith, Steve. 2010. [Email to Katharine Stone]. June 30. Regarding fire and para grass in Florida. Canal Point, FL: South Florida Water Management District, DuPuis Reserve, Invasive Species Operations. On file with: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory, Missoula, MT; FEIS files. [80292]

95. Stickney, Peter F. 1989. Seral origin of species comprising secondary plant succession in Northern Rocky Mountain forests. FEIS workshop: Postfire regeneration. Unpublished draft on file at: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory, Missoula, MT. 10 p. [20090]

96. Sutton, David L. 1996. Growth of torpedograss from rhizomes planted under flooded conditions. Journal of Aquatic Plant Management. 34: 50-53. [81205]

97. Toth, Louis A. 2007. Conversion of torpedograss (Panicum repens) to submerged aquatic vegetation in an operational stormwater treatment area for the Everglades. Journal of Aquatic Plant Management. 45: 119-121. [81290]

98. Toth, Louis A. 2007. Establishment of submerged aquatic vegetation in Everglades stormwater treatment areas: value of early control of torpedograss (Panicum repens). Journal of Aquatic Plant Management. 45: 17-20. [81289]

99. Tu, Mandy; Hurd, Callie; Randall, John M., eds. 2001. Weed control methods handbook: tools and techniques for use in natural areas. Davis, CA: The Nature Conservancy. 194 p. [37787]

100. Tyser, Robin W.; Worley, Christopher A. 1992. Alien flora in grasslands adjacent to road and trail corridors in Glacier National Park, Montana (U.S.A.). Conservation Biology. 6(2): 253-262. [19435]

101. U.S. Department of Agriculture, Forest Service. 2001. Guide to noxious weed prevention practices. Washington, DC: U.S. Department of Agriculture, Forest Service. 25 p. Available online: https://www.fs.usda.gov /invasivespecies/documents/FS_WeedBMP_2001.pdf [2009, November 19]. [37889]

102. U.S. Department of Agriculture, Natural Resources Conservation Service. 2011. PLANTS Database, [Online]. Available: https://plants.usda.gov /. [34262]

103. Van Driesche, Roy; Lyon, Suzanne; Blossey, Bernd; Hoddle, Mark; Reardon, Richard, tech. coords. 2002. Biological control of invasive plants in the eastern United States. Publication FHTET-2002-04. Morgantown, WV: U.S. Department of Agriculture, Forest Service, Forest Health Technology Enterprise Team. 413 p. Available online: http://www.invasive.org/eastern/biocontrol/index.html [2009, November 19]. [54194]

104. Wagner, Warren L.; Herbst, Derral R.; Sohmer, S. H., eds. 1999. Manual of the flowering plants of Hawai'i. [Revised edition]. Volume 2. Bishop Museum Special Publication 97. Honolulu, HI: University of Hawai'i Press; Bishop Museum Press. 929 p. [70168]

105. Weber, Ewald. 2003. Invasive plant species of the world: a reference guide to environmental weeds. Cambridge, MA: CABI Publishing. 548 p. [71904]

106. Wilcut, J. W.; Truelove, B.; Davis, D. E. 1985. Cogongrass and torpedograss troublesome in coastal area. Highlights of Agricultural Research. 32(3): 9. [51051]

107. Wilcut, John W.; Dute, Roland R.; Truelove, Bryan; Davis, Donald E. 1988. Factors limiting the distribution of cogongrass, Imperata cylindrica, and torpedograss, Panicum repens. Weed Science. 36(5): 577-582. [50911]

108. Wilcut, John W.; Truelove, Bryan; Davis, Donald E.; Williams, John C. 1988. Temperature factors limiting the spread of cogongrass (Imperata cylindrica) and torpedograss (Panicum repens). Weed Science. 36(1): 49-55. [50921]

109. Wilcut, John William. 1986. The biology of cogongrass, torpedograss, and johnsongrass. Auburn, AL: Auburn University. 182 p. Dissertation. [81143]

110. Wilson, Linda M.; McCaffrey, Joseph P. 1999. Biological control of noxious rangeland weeds. In: Sheley, Roger L.; Petroff, Janet K., eds. Biology and management of noxious rangeland weeds. Corvallis, OR: Oregon State University Press: 97-115. [35715]

111. Wolverton, B. C.; Bounds, Byron Keith. 1988. Aquatic plants for pH adjustment and removal of toxic chemicals and dissolved minerals from water supplies. Journal of the Mississippi Academy of Sciences. 33: 71-80. [81330]

112. Wu, Z. Y.; Raven, P. H.; Hong, D. Y., eds. 2011. Flora of China, [Online]. Volumes 1-25. Beijing: Science Press; St. Louis, MO: Missouri Botanical Garden Press. In: eFloras. St. Louis, MO: Missouri Botanical Garden; Cambridge, MA: Harvard University Herbaria (Producers). Available: http://www.efloras.org/flora_page.aspx?flora_id=2 and http://flora.huh.harvard.edu/china. [72954]

113. Wunderlin, R. P.; Hansen, B. F. 2008. Atlas of Florida vascular plants, [Online]. In: PlantAtlas.org. Tampa, FL: University of South Florida, Institute for Systematic Botany (Producer). Available: http://www.florida.plantatlas.usf.edu/ [2009, October 15]. [54934]

114. Wunderlin, Richard P. 1982. Guide to the vascular plants of central Florida. Tampa, FL: University Presses of Florida. 472 p. [13125]

115. Wunderlin, Richard P.; Hansen, Bruce F. 2003. Guide to the vascular plants of Florida. 2nd ed. Gainesville, FL: The University of Florida Press. 787 p. [69433]

116. Zomlefer, Wendy B.; Giannasi, David E.; Bettinger, Kelly A.; Echols, S. Lee; Kruse, Lisa M. 2008. Vascular plant survey of Cumberland Island National Seashore, Camden County, Georgia. Castanea. 73(4): 251-282. [75096]