Thomas G. Barnes

Strategies to Convert Exotic Grass Pastures to Tall Grass Prairie Communities1

Abstract Exotic cool- and warm-season grasses have been used throughout the eastern United States as an improved forage in pastures and for wildlife habitat and erosion control. Several of these grasses, including tall fescue are invasive and diminish native grassland biodiversity. This article presents three strategies for reconstructing or rehabilitating native grasslands using herbicides. A variety of herbicides including glyphosate, imazapic, and clethodim, alone or in combination, are effective in killing tall fescue. Imazapic and clethodim show promise for removing tall fescue from native grasslands. Imazapic is more effective when applied with a surfactant and when tall fescue is burned before herbicide application. A standard recommendation for converting tall fescue to native warm-season grasses (NWSG) is to burn tall fescue in late winter, followed by application of 0.2 kg ai/ha imazapic with surfactant and a small amount of nitrogen a month later. The native grasses are seeded directly into the dying and dead sod with a no-till drill. An alternative method is to apply 2.2 kg ai/ha glyphosate to kill the fescue and use 0.067 kg ai/ha imazapic at seeding for weed control. NWSG can be effectively established using conventional tillage by preparing a firm seedbed, drilling or broadcasting the seed directly into the seedbed, and applying 0.067 kg ai/ha imazapic for weed control. Nomenclature: Clethodim; glyphosate; imazapic; tall fescue, Festuca arundinacea Schreb. #3 668 FESAR. Additional index words: Bahiagrass, bermudagrass, fescue conversion, herbicides, native warm-season grasses, quackgrass. Abbreviation: NWSG, native warm-season grasses.

Using Herbicides to Rehabilitate Native Grasslands

Abstract One of the threats to native biodiversity in native grasslands is the abundance of exotic plants. The objectives of this study were to evaluate the efficacy of imazapic, clethodim, and sulfosulfuron for removing tall fescue (Festuca arundinacea Schreb.) and releasing the native warm-season grasses (NWSG) and to document which species of broadleaf plants survive a post-emergence treatment of 0.2 kg ai/ha of imazapic or 0.03 kg ai/ha sulfosulfuron. All three herbicides reduced the amount of total vegetative cover after the first growing season, but there were no differences by the end of the second growing season. All herbicide-treated plots had less tall fescue than untreated control plots after the first and second growing seasons. After the first growing season, imazapic- and sulfosulfuron-treated plots had less tall fescue than clethodim-treated plots, but there was no difference by the end of the second growing season. NWSG increased the most in the imazapic-treated plots and second most in the sulfosulfuron-treated plots. NWSG did not increase in the clethodim-treated plots when compared to the controls after the first growing season. All herbicide treatments increased the amount of bare ground, and the clethodim was the least harmful to broadleaf plants. These herbicides show promise as a useful tool for removing tall fescue from remnant grasslands and enhancing NWSG and selected broadleaf plants in native grassland systems.

Herbicide and fire effects on smooth brome (Bromus inermis) and Kentucky bluegrass (Poa pratensis) in invaded prairie remnants.

Abstract Smooth brome and Kentucky bluegrass are introduced cool-season perennial grasses known to invade grasslands throughout North America. During the fall of 2005 and spring of 2006, we implemented a restoration study at six native prairie sites in eastern South Dakota that have been invaded by smooth brome and Kentucky bluegrass. Treatments included five herbicide combinations, a fall prescribed burn, and an untreated control to determine the potential of each for renovation of invaded native grasslands. Herbicide treatments tested were sulfosulfuron, imazapyr, imazapic + sulfosulfuron, and imazapyr + imazapic, and were applied in late September 2005 and mid-May 2006. Untreated control plots averaged 64% (± 3.1) smooth brome cover and 38% (± 5.5) Kentucky bluegrass cover after the third growing season. Smooth brome cover in herbicide treated plots ranged from 6 to 23% and Kentucky bluegrass cover ranged from 15 to 35% after the third growing season. Smooth brome cover was 20% (± 2.9) and Kentucky bluegrass cover was 19% (± 4.0) in burned plots after the third growing season. Spring and fall treatments had similar native plant cover after three growing seasons. Spring and fall application of 0.33 kg ai ha−1 imazapyr and 0.10 kg ai ha−1 imazapic + 0.16 kg ai ha−1 imazapyr had ≤ 10% smooth brome cover and increased native species cover after three growing seasons. Herbicides were effective at reducing cover of smooth brome and Kentucky bluegrass, and can be incorporated with other management strategies to restore prairie remnants. Nomenclature: imazapic, (±)-2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-5-methyl-3-pyridinecarboxylic acid; imazapyr, (±)-2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-3-pyridinecarboxylic acid; sulfosulfuron, (±)-1-(4,6-dimethoxypyrimidin-2-yl)-3-[(2-ethanesulfonyl-imidazo[1,2-a]pyridine-3-yl)sulfonylurea; Kentucky bluegrass, Poa pratensis L. POAPR. smooth brome, Bromus inermis Leyss. BROIN Interpretive Summary: Smooth brome and Kentucky bluegrass are introduced forage grasses that are known to invade native grasslands throughout North America. Effective management strategies for controlling these species in native grasslands have not been developed. In this study we compared the efficacy of prescribed fire and multiple herbicide combinations to control smooth brome and Kentucky bluegrass while minimizing harm to native species. We evaluated spring and fall application of herbicides to determine if they have any significant effect (positive or negative) on these species, as well as native species. Our results indicate that several herbicide combinations show potential for restoring native prairie fragments, but prescribed fire did not provide adequate long-term control. Applications of imazapyr herbicide resulted in the most consistent control of smooth brome. Initial reductions in Kentucky bluegrass cover were observed during the study, but cover increased throughout the study and likely will require further management to achieve desired control. Spring-treated plots had much more bare ground and visible injury to surviving plants than did the fall treatments after the first growing season. These herbicide treatments reduced cover of smooth brome and Kentucky bluegrass and can be integrated with other strategies to restore native prairie remnants.

Natural Grassland Response to Herbicides and Application Timing for Selective Control of Tall Fescue, an Invasive Cool-Season Grass

Abstract Natural grasslands are one of the most threatened ecosystems in North America. Conservation efforts are often hampered by exotic plant invasions in existing remnant natural grasslands. Tall fescue [Schedonorus phoenix (Scop.) Holub.] is an introduced cool-season (C3) forage/turf grass which readily invades natural grasslands in Kentucky and neighboring states. Our study objectives were to (1) compare the efficacy and application timing effect of clethodim to that of imazapic to selectively remove tall fescue from natural grasslands and (2) evaluate the response of the nontarget grassland plant community (i.e., native grass and forb canopy cover) following herbicide treatments. Clethodim and imazapic treatments consisted of early (April 4, 2001) and late (April 20, 2001) applications, and these were applied at 0.23 and 0.21 kg ai ha−1, respectively. Both herbicides reduced tall fescue cover (P ≤ 0.05); herbicide application timing had no effect on herbicide efficacy to control tall fescue. Native grass cover was higher (P ≤ 0.05) in all herbicide-treated plots compared to the untreated controls, except for the late clethodim-treated plots. All herbicide treatments increased forb abundance compared to controls. Spring applications of clethodim were equally effective to those of imazapic at controlling tall fescue in natural grasslands. Imazapic released native grasses better than clethodim, whereas clethodim was better at increasing forb abundance. Furthermore, early clethodim treatments had fewer nontarget effects on native C4 grasses compared to late clethodim treatments. Overall, clethodim shows promise as a beneficial management tool for tall fescue control in C4-dominated natural grasslands. Nomenclature: Clethodim; imazapic; tall fescue, Schedonorus phoenix (Scop.) Holub

No-till Establishment of Native Warm-Season Grasses In Tall Fescue Fields: First-year results indicate value of new herbicide

Following a spring prescribed burn and a pre-emergence application of Plateau herbicide, Brian Washburn uses a Tye no-till drill to seed the research plots with native warmseason grasses. Photo by Daniel Bishop p to the release of PlateauTM herbicide, converting grasslands dominated by tall fescue (Festuca arundinacea) to native warm-season grasses (NWSGs) took several years. Native warm-season grasses can now be established in one growing season using Plateau herbicide. We present information in this paper that shows Plateau eliminated tall fescue and provided post-emergence weed control, allowing NWSGs (50 percent cover) to establish during the first year. More than 97 percent of tallgrass prairie in the United States has been destroyed, most acreage having been plowed down to create cropland or converted to pasture dominated by exotic, cool-season grasses (Sampson and Knopf, 1996). In the lower Midwest and upper South, many cool-season pastures were created by seeding tall fescue. This European grass has been planted on more than 35 million acres (Ball and others, 1993) for hay, pasture, surface-mine reclamation, and revegetation of Conservation Reserve Program (CRP) lands (Burns and Chamblee, 1979). More than 95 percent of all tall fescue fields are infected with a fungal endophyte (Neotyphodiurn coenophialum) that produces toxins that can cause weight loss, reproductive problems, and a variety of diseases in livestock and domestic animals (see Ball and others, 1993 for a review). Furthermore, tall fescue does not provide habitat for birds and has been shown to affect the nutritional ecology of birds (Barnes and others, 1995; Conover and Messmer, 1996). There is a strong interest in prairie restoration (Lutz, 1989). Planting NWSGs and forbs is an integral component this restoration (Packard and Mutel, 1997). In the past, however, NWSGs have been known to establish slowly and are susceptible to competition from weeds during the first growing season (Martin and others, 1982). Furthermore, the establishment of these grasses on highly erodible soils, where traditional seedbed preparations are not possible, requires no-till seeding techniques (Packard and Mutel, 1997). Prior to establishing NWSGs in tall fescuedominated fields, the fescue must be killed because it is an aggressive, sod-forming grass that has a competitive advantage over other plants as a result of the endophytic fungus (Ball and others, 1993; Smith, 1989). A single spring application of glyphosate at 3 to 5 pints/acre has been shown to kill 80 to 95 percent of tall fescue in Kentucky (Madison and others, 1995), Missouri (Defelice and Henning, 1990), and Georgia (Smith, 1989). A relatively new herbicide, AC 263,222 (product name Plateau), may be especially useful in NWSG establishment because several species of NWSGs and native forbs are tolerant to this herbicide (Vollmer, 1998). Masters and others

Restoring Native Plant Communities in Smooth Brome (Bromus inermis)–Dominated Grasslands

Abstract Smooth brome (Bromus inermis) is an introduced, cool-season perennial, sod-forming grass that has been shown to invade both native cool-and warm-season grasslands throughout North America. During the fall of 2005 through spring 2007, we implemented a smooth brome removal study at five sites in eastern South Dakota. Sites were selected to represent a range of soil and environmental conditions. Seven fall herbicide treatments, five spring herbicide treatments, an untreated plot that was planted with a native seed mix, and an untreated control that received no herbicide or seed addition were applied at each location in fall 2005/spring 2006 and fall 2006/spring 2007. Based upon first-year results, three fall herbicide treatments and two spring herbicide treatments were added in fall 2006/spring 2007. Sites were seeded with a native plant mix within 2 wk following spring herbicide treatment. Smooth brome cover in untreated plots ranged from 73 to 99% at the conclusion of the study. Smooth brome cover on herbicide-treated plots ranged from 0 to 84% on 2005/2006 plots and 0 to 98% on 2006/2007 plots after three growing seasons. Native plant response varied by site and treatment, possibly due to competition from exotic weeds. Although several herbicides show promise for control of smooth brome, future response of native plants will be important in determining the proper timing and herbicide combination. Nomenclature: Smooth brome, Bromus inermis Leyss. BROIN Interpretive Summary: Smooth brome (Bromus inermis) is an introduced, cool-season perennial, sod-forming grass that has been widely planted as a forage species. However, it is also an aggressive grass that can rapidly invade native cool-and warm-season grasslands throughout North America. Much work has been devoted to developing management strategies for smooth brome. Many of the past studies utilized herbicides that are no longer labeled for use in certain situations, or required conversion of invaded areas to agriculture for several years prior to planting native species. New herbicides have the potential to allow direct conversion of smooth brome–dominated areas to native plant communities without prior conversion to agriculture. In this study we compared the efficacy of several herbicide combinations to control smooth brome, while allowing the establishment of planted native species. We also evaluated spring and fall application timings to determine if they have any significant effect (positive or negative) on smooth brome control, as well as native plant establishment. Several herbicide combinations show potential for controlling smooth brome and allowing establishment of planted native species. Treatments with sulfosulfuron + glyphosate and imazapyr provided the most consistent smooth brome control during the study. Treatments that showed the greatest reduction in smooth brome also tended to have the highest cover of planted species. Caution still has to be exercised when using high rates of imazapyr, as it can cause injury to planted species. These results will allow managers to convert smooth brome–dominated fields to native plant communities without first converting them to agriculture, decreasing the amount of time necessary to achieve a successful conversion.

Postemergence Tall Fescue (Festuca arundinacea) Control at Different Growth Stages with Glyphosate and AC 263,2221

Abstract: Effective methods are needed to eradicate tall fescue (Festuca arundinacea) and convert tall fescue fields into habitats more suitable to wildlife species. The objectives of this study were to determine the efficacy of (1) a single glyphosate application during the spring or fall and (2) AC 263,222, alone and in combination with glyphosate, applied during four different tall fescue growth stages for control of established tall fescue. Studies were conducted during 1996 to 1998 in fields dominated by tall fescue located in central Kentucky. Pre- and posttreatment plant communities were described to quantify differences in vegetative characteristics due to herbicide applications. Glyphosate at 2.2 kg ai/ha applied during the spring or fall was effective in reducing tall fescue to less than 12% cover. AC 263,222 at 0.2 kg ai/ha, AC 263,222 at 0.2 kg/ha plus glyphosate at 0.6 kg/ha, or AC 263,222 at 0.2 kg/ha plus glyphosate at 1.1 kg/ha applied during the spring growth, boot, summer dormancy, and fall growth stages were equally effective, reducing tall fescue cover to less than 3% at 2 to 7 mo after treatment. Glyphosate and AC 263,222 are effective tools for the initial removal of tall fescue. Nomenclature: AC 263,222, (±)-2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-5-methyl-3-pyridinecarboxylic acid; glyphosate, N-(phosphonomethyl)glycine; tall fescue, Festuca arundinacea Schreb. #3 FESAR. Additional index words: Fescue conversion. Abbreviations: NWSG, native warm-season grasses; OM, organic matter; SE, standard error of the mean; MAT, months after treatment.

Native Grass and Forb Response to Pre-Emergent Application of Imazapic and Imazapyr

ABSTRACT: Grassland restoration attempts to rehabilitate and/or re-create biologically diverse native plant communities using a variety of management techniques including seeding, burning, grazing, and most recently using herbicides. Herbicides are an important tool for suppressing weed competition for initial seedling growth and removing exotic species in native plant communities. Little information is available on which species of native plants can endure a pre-emergent application of the imidazolinone herbicides. In spring 2006, we initiated a study testing responses of three native grasses and three native forbs to pre-emergent treatments of 0.035 kg ai/ha imazapic, 0.07 kg ai/ha imazapic, and 0.07 kg ai/ha imazapyr. Seedling establishment was monitored at 5 and 14 months after treatment and weed cover was monitored at 2.5, 5 and 14 months after treatment. There were no differences in the number of seedlings found in the untreated plots compared to all the herbicide-treated plots and there were no differences in seedling densities of green needlegrass (Nassella viridula) with the exception of the high imazapic treatment. Showy tick trefoil (Desmodium canadense) and Canada milk vetch (Astragalus crassicarpus) also appear to be able to tolerate applications of all herbicide treatments. There was less weed cover in the herbicide-treated plots when compared to the untreated control plots. This information provides managers options to include these species in initial seeding or restoration projects using these herbicides which may increase diversity and reduce restoration projects cost in the long term.

The effect of herbicide on the re-establishment of native grasses in the Blackland Prairie.

ABSTRACT: The Blackland Prairie of east-central Texas, the southernmost tip of the once vast North American Tallgrass Prairie, now covers only 1% of its original 6.8 million hectares. Thus, there is considerable interest in restoration and re-establishment of this endangered ecosystem. In a randomized complete block field experiment conducted near San Marcos, Texas, we tested the effectiveness of the post-emergent herbicide imazapic on weed control, establishment, and growth of four C4 warm-season grasses native to the Blackland Prairie (Andropogon gerardii, Sorghastrum nutans, Schizachyrium scoparium, and Bouteloua curtipendula). Treatment with three different levels of imazapic (0.07, 0.092, and 0.138 kg ai/ha) all significantly increased seedling density of native grasses, and low-to-medium levels of imazapic increased seedling shoot growth and flowering relative to water controls. End-of-season aboveground biomass of native grasses also increased with imazapic treatment while that of broadleaf species decreased. However, shoot biomass of exotic C4 grasses (principally Bothriochloa ischaemum and Dichanthium sericeum), the dominant species of this site prior to study, was not significantly affected by imazapic treatment. Despite vigorous site preparation and pretreatment with a broad-spectrum herbicide (Roundup®), these exotic C4 bluestem grasses continued to dominate all treatment plots. These findings indicate that while imazapic is beneficial for native warm season grass establishment, it is inadequate to effectively control these exotic bluestems, which are abundant on many sites once occupied by Blackland Prairie. Successful restoration of native grasses in the Blackland Prairie will, therefore, require more effective means of controlling or eliminating these aggressive exotic species.

Herbicide Treatment and Timing for Controlling Kentucky Bluegrass (Poa pratensis) and Tall Fescue (Festuca arundinacea) in Cool Season Grasslands of Central Kentucky, USA

ABSTRACT: The goal of this study was to evaluate the efficacy of four herbicides for controlling invasive Kentucky bluegrass (Poa pratensis L.) and tall fescue (Festuca arundinacea Schreb.) in idle grasslands by monitoring post-treatment plant communities. Experiments were conducted in two remnant savannas in central Kentucky. With the exception of domestic grazing, these sites were chosen because they were undisturbed by agriculture and development. Single treatments of 0.2 kg ai/ha imazapic, 0.2 kg ai/ha clethodim, 0.2 kg ai/ha imazapic + 1.1 kg ai/ha glyphosate, 0.03 kg ai/ha sulfosulfuron, and an untreated control were implemented in fall 2004 and spring and summer 2005 at each site in a randomized complete block design. Plant communities were monitored 3, 10, 12, 14, and 15 months after the final treatments were implemented. At 15 months post-treatment, tall fescue cover was reduced in all treatment plots relative to the untreated control, with the greatest reduction in tall fescue cover occurring in the summer treatment plots. Spring applications of each herbicide were more effective for Kentucky bluegrass control than summer or fall treatments. All herbicide treatments reduced Kentucky bluegrass compared to untreated plots. The most effective herbicide treatment was imazapic + glyphosate, which reduced Kentucky bluegrass cover to less than 7%. However, the resulting bare ground facilitated invasions by other aggressive exotic species, notably musk thistle (Carduus nutans L.). Spring applications of clethodim reduced Kentucky bluegrass cover relative to the untreated plots, and resulted in the highest number of native plant species compared to all other plots. This conservation of forb cover provided by clethodim may be of importance in managing areas impaired by this aggressive, invasive grass. Nomenclature: Carduus nutans L., Clethodim, glyphosate, imazapic, Kentucky bluegrass, musk thistle, Poa pratensis L., sulfosulfuron, tall fescue